Ashrae 2003 HVAC applications

• Chapter 32, Geothermal Energy, updated for new research, has expanded text on ground-source heat pumps, covering site char-acterization, thermal testing, load calculations, borehole op

MAIN MENU

HELP TERMINOLOGY Contributors

Preface

Technical Committees, Task Groups, and

Technical Resource Groups

COMFORT APPLICATIONS

• A01 Residences

• A02 Retail Facilities

• A03 Commercial and Public Buildings

• A04 Places of Assembly

• A05 Hotels, Motels, and Dormitories

• A06 Educational Facilities

• A07 Health Care Facilities

• A08 Justice Facilities

• A09 Surface Transportation

• A10 Aircraft

• A11 Ships

INDUSTRIAL APPLICATIONS

• A12 Industrial Air Conditioning

• A13 Enclosed Vehicular Facilities

• A14 Laboratories

• A15 Engine Test Facilities

• A16 Clean Spaces

• A17 Data Processing and Electronic Office Areas

• A18 Printing Plants

• A19 Textile Processing Plants

• A20 Photographic Material Facilities

• A21 Museums, Libraries, and Archives

• A22 Environmental Control for Animals and Plants

• A23 Drying and Storing Selected Farm Crops

• A24 Air Conditioning of Wood and Paper Product

Facilities

• A25 Power Plants

• A26 Nuclear Facilities

• A27 Mine Air Conditioning and Ventilation

• A28 Industrial Drying Systems

• A29 Ventilation of the Industrial Environment

• A30 Industrial Local Exhaust Systems

2003 HVAC Applications

(SI Edition)

2003 HVAC Applications

(SI Edition)

ENERGY-RELATED APPLICATIONS

• A32 Geothermal Energy

• A33 Solar Energy Use

• A34 Thermal Storage

BUILDING OPERATIONS AND MANAGEMENT

• A35 Energy Use and Management

• A36 Owning and Operating Costs

• A37 Testing, Adjusting, and Balancing

• A38 Operating and Maintenance Management

• A39 Computer Applications

• A40 Building Energy Monitoring

• A41 Supervisory Control Strategies and Optimization

• A42 New Building Commissioning

GENERAL APPLICATIONS

• A43 Building Envelopes

• A44 Building Air Intake and Exhaust Design

• A45 Control of Gaseous Indoor Air

Contaminants

• A46 Design and Application of Controls

• A47 Sound and Vibration Control

• A48 Water Treatment

• A49 Service Water Heating

• A50 Snow Melting and Freeze Protection

• A51 Evaporative Cooling Applications

• A52 Fire and Smoke Management

• A53 Radiant Heating and Cooling

• A54 Seismic and Wind Restraint Design

• A55 Electrical Considerations

• A56 Codes and Standards

The American Society of Heating, Refrigerating and

Air-Condi-tioning Engineers is the world’s foremost technical society in the

fields of heating, ventilation, air conditioning, and refrigeration Its

members worldwide are individuals who share ideas, identify

needs, support research, and write the industry’s standards for

test-ing and practice The result is that engineers are better able to keep

indoor environments safe and productive while protecting and

pre-serving the outdoors for generations to come

One of the ways that ASHRAE supports its members’ and

indus-try’s need for information is through ASHRAE Research

Thou-sands of individuals and companies support ASHRAE Research

annually, enabling ASHRAE to report new data about materialproperties and building physics and to promote the application ofinnovative technologies

The chapters in ASHRAE Handbooks are updated through theexperience of members of ASHRAE technical committees andthrough results of ASHRAE Research reported at ASHRAE meet-ings and published in ASHRAE special publications and in

ASHRAE Transactions

For information about ASHRAE Research or to become a ber, contact ASHRAE, 1791 Tullie Circle, Atlanta, GA 30329; tele-phone: 404-636-8400; www.ashrae.org

mem-The 2003 ASHRAE Handbook

The 2003 ASHRAE Handbook—HVAC Applications contains

chapters on a broad range of applications, written to help design

engineers use equipment and systems described in other Handbook

volumes This edition includes two new chapters, Chapter 8, Justice

Facilities, and Chapter 55, Electrical Considerations Nearly every

Applications chapter has been revised for current requirements and

techniques The ASHRAE technical committees that prepare

chap-ters have provided new information, clarified existing information,

deleted obsolete material, and reorganized chapters to make the

Handbook more understandable and easier to use Some of the

revi-sions are as follows:

• Chapter 7, Health Care Facilities, contains extensive updates to

HVAC requirements for hospitals, including new temperature and

humidity design guidelines for various facility areas

• Chapter 8, Justice Facilities, is a new chapter with information on

related terminology, requirements, and design considerations for

these facilities

• Chapter 14, Laboratories, has new data on biological safety

cab-inets and scale-up laboratories, and research updates on exhaust

stack location and caging system ventilation

• Chapter 21, Museums, Libraries, and Archives, rewritten,

con-tains more information on pollutant sources, indoor air quality,

and threats to artifacts

• Chapter 26, Nuclear Facilities, has updates for regulatory

require-ments plus added information on international reactor designs

and standards, cascade ventilation, heavy water reactors, and

gas-cooled reactor HVAC systems

• Chapter 27, Mine Air Conditioning and Ventilation, updated for

current practice, has expanded text on ventilation system design,

health and safety, and new examples, including one using the

fac-tor-of-merit method for designing direct-contact heat exchangers

• Chapter 29, Ventilation of the Industrial Environment, has been

completely rewritten for clarity and ease of use

• Chapter 30, Industrial Local Exhaust Systems, has been

exten-sively revised and refocused for ease of use

• Chapter 31, Kitchen Ventilation, has new cooking emission and

hood flow rate information, plus schlieren photographs of hood

tests showing actual containment and spillage

• Chapter 32, Geothermal Energy, updated for new research, has

expanded text on ground-source heat pumps, covering site

char-acterization, thermal testing, load calculations, borehole options,

design strategy, water quality, well pump control, and horizontal

closed-loop systems

• Chapter 34, Thermal Storage, contains updates for research,

oper-ation and control, and combustion turbine inlet air cooling in

stor-age applications

• Chapter 35, Energy Use and Management, retitled and rewritten,

also has updated DOE energy consumption data

• Chapter 36, Owning and Operating Costs, contains new servicelife considerations, energy cost analysis resources, and updatesfor deregulation issues and ASHRAE research

• Chapter 37, Testing, Adjusting, and Balancing, has a rewrittenhydronic balancing section, and updated text on instrumentationand sound and vibration testing

• Chapter 38, Operation and Maintenance Management, tially revised, has a new section on results-oriented maintenancemanagement

substan-• Chapter 39, Computer Applications, has new and revised mation on hardware, development tools, networking, the Internet,web sites, and application software and utilities for HVAC designtasks, simulation, business management, and monitoring andcontrol

infor-• Chapter 42, New Building Commissioning, rewritten andexpanded, has more information on commissioning at everystage, from owner project requirement development throughoccupancy and operation

• Chapter 44, Building Air Intake and Exhaust Design, has updatesfrom ASHRAE research, covering dilution equations, stackheight estimating, air intake design, and the dilution effects ofarchitectural screens

• Chapter 47, Sound and Vibration Control, updated for currenttechnology and standards, also has new sections on emergencygenerators and plumbing system noise

• Chapter 50, Snow Melting and Freeze Protection, retitled, nowcovers freeze protection systems, and has updates from ASHRAEresearch on transient analysis of snow-melting performance

• Chapter 55, Electrical Considerations, a new chapter on buildingelectrical issues for HVAC equipment, has sections on electricalprinciples, codes, performance, safety, power quality, motor-starting effects, and rates

This Handbook is published both as a bound print volume and inelectronic format on a CD-ROM It is available in two editions: oneusing inch-pound (I-P) units of measurement, the other using theInternational System of Units (SI)

Corrections to the 2000, 2001, and 2002 Handbooks are posted

on the ASHRAE web site at http://www.ashrae.org Corrections for

this volume will be reported in the 2004 ASHRAE Handbook— HVAC Systems and Equipment and on the ASHRAE web site.

To make suggestions for improving a chapter or for information

on how you can help revise a chapter, please comment using a form

on the ASHRAE web site; or e-mail mowen@ashrae.org; or write

to Handbook Editor, ASHRAE, 1791 Tullie Circle, Atlanta, GA30329; or fax 404-321-5478

Mark S OwenASHRAE Handbook Editor

Copyright © 2003, ASHRAE

In addition to the Technical Committees, the following individuals contributed significantly

to this volume The appropriate chapter numbers follow each contributor’s name

Trueman Engineering Services

Phoenix Controls Corporation

Clayton Group Services

Claude Laval Corporation

ASHRAE HANDBOOK COMMITTEE

Kenneth W Cooper, Chair

2003 HVAC Applications Volume Subcommittee: Kenneth W Cooper, Chair

ASHRAE HANDBOOK STAFF

Nancy F Thysell, Typographer/Page Designer Barry Kurian, Manager and Jayne E Jackson

Publishing Services

W Stephen Comstock,

Director, Communications and Publications

Publisher

PACE-CONDITIONING systems for residential use vary with

Sboth local and application factors Local factors include energy

source availability (present and projected) and price; climate;

socio-economic circumstances; and the availability of installation and

maintenance skills Application factors include housing type,

con-struction characteristics, and building codes As a result, many

dif-ferent systems are selected to provide combinations of heating,

cooling, humidification, dehumidification, and air filtering This

chapter emphasizes the more common systems for space

condition-ing of both scondition-ingle-family (i.e., traditional site-built and modular or

manufactured homes) and multifamily residences Low-rise

multi-family buildings generally follow single-multi-family practice because

constraints favor compact designs Retrofit and remodeling

con-struction also adopt the same systems as those for new concon-struction,

but site-specific circumstances may call for unique designs

Systems

Common residential systems are listed in Table 1 Three

gener-ally recognized groups are central forced air, central hydronic, and

zoned systems System selection and design involve such key

deci-sions as (1) source(s) of energy, (2) means of distribution and

deliv-ery, and (3) terminal device(s)

Climate determines the services needed Heating and cooling are

generally required Air cleaning (by filtration or electrostatic

devices) can be added to most systems Humidification, which can

also be added to most systems, is generally provided in heating

sys-tems only when psychrometric conditions make it necessary for

comfort and health (as defined in ASHRAE Standard 55) Cooling

systems usually dehumidify as well Typical residential installations

are shown in Figures 1 and 2

Figure 1 shows a gas furnace, a split-system air conditioner, a

humidifier, and an air filter The system functions as follows: Air

from the space enters the equipment through a return air duct (1)

It passes initially through the air filter (2) The circulating blower(3) is an integral part of the furnace (4), which supplies heat duringwinter An optional humidifier (10) adds moisture to the heated air,which is distributed throughout the home via the supply duct (9).When cooling is required, the circulating air passes across the evap-orator coil (5), which removes heat and moisture from the air.Refrigerant lines (6) connect the evaporator coil to a remote con-densing unit (7) located outdoors Condensate from the evaporator

is removed through a drainline with a trap (8)

Figure 2 shows a split-system heat pump, supplemental electricresistance heaters, a humidifier, and an air filter The system func-tions as follows: Air from the space enters the equipment throughthe return air duct (1) and passes through a filter (2) The circulatingblower (3) is an integral part of the indoor unit (or air handler) ofthe heat pump (4), which supplies heat via the indoor coil (6) duringthe heating season Optional electric heaters (5) supplement heatfrom the heat pump during periods of low ambient temperature andcounteract airstream cooling during the defrost cycle An optionalhumidifier (10) adds moisture to the heated air, which is distributedthroughout the home via the supply duct (9) When cooling isrequired, the circulating air passes across the indoor coil (6), whichremoves heat and moisture from the air Refrigerant lines (11)connect the indoor coil to the outdoor unit (7) Condensate from theindoor coil is removed through a drainline with a trap (8).Single-package systems, where all equipment is contained inone cabinet, are also popular in the United States They are used

The preparation of this chapter is assigned to TC 7.6, Unitary and Room

Air Conditioners and Heat Pumps.

Central Forced Air

Central Hydronic Zoned

Most common

energy

sources

Gas Oil Electricity Resistance Heat pump

Gas Oil Electricity Resistance Heat pump

Gas Electricity Resistance Heat pump

system

Piping or Free delivery Terminal

devices

Diffusers Registers Grilles

Radiators Radiant panels Fan-coil units

Included with product or same

as forced-air or hydronic systems

Fig 1 Typical Residential Installation of Heating, Cooling, Humidifying, and Air Filtering System

Fig 1 Typical Residential Installation of Heating, Cooling,

Humidifying, and Air Filtering System

Copyright © 2003, ASHRAE

extensively in areas where residences have duct systems in

crawl-spaces beneath the main floor and in areas such as the Southwest,

where typically rooftop-mounted packages connect to attic duct

systems

Central hydronic heating systems are popular both in Europe and

in parts of North America where central cooling has not normally

been provided New construction, especially in multistory homes,

now typically includes central cooling

Zoned systems are designed to condition only part of a home at

any one time They may consist of individual room units or central

systems with zoned distribution networks Multiple central systems

that serve individual floors or the sleeping and common portions of

a home separately are sometimes used in large single-family houses

The source of energy is a major consideration in system

selec-tion For heating, gas and electricity are most widely used, followed

by oil, wood, solar energy, geothermal energy, waste heat, coal,

district thermal energy, and others Relative prices, safety, and

envi-ronmental concerns (both indoor and outdoor) are further factors in

heating energy source selection Where various sources are

avail-able, economics strongly influence the selection Electricity is the

dominant energy source for cooling

Equipment Sizing

The heat loss and gain of each conditioned room and of ductwork

or piping run through unconditioned spaces in the structure must be

accurately calculated in order to select equipment with the proper

heating and cooling capacity To determine heat loss and gain

accu-rately, the floor plan and construction details must be known The

plan should include information on wall, ceiling, and floor

construc-tion as well as the type and thickness of insulaconstruc-tion Window design

and exterior door details are also needed With this information, heat

loss and gain can be calculated using the Air-Conditioning

Contrac-tors of America (ACCA) Manual J or similar calculation

proce-dures To conserve energy, many jurisdictions require that the

building be designed to meet or exceed the requirements of

ASHRAE Standard 90.2, Energy-Efficient Design of New

Low-Rise Residential Buildings, or similar requirements

Proper matching of equipment capacity to the building heat loss

and gain is essential The heating capacity of air-source heat pumps

is usually supplemented by auxiliary heaters, most often of the

elec-tric resistance type; in some cases, however, fossil fuel furnaces or

solar systems are used

Undersized equipment will be unable to maintain the intendedindoor temperature under conditions of extreme outdoor tempera-tures Some oversizing may be desirable to enable recovery fromsetback and to maintain indoor comfort during outdoor conditionsthat are more extreme than the nominal design conditions Grosslyoversized equipment can cause discomfort because of short on-times, wide indoor temperature swings, and inadequate dehumidi-fication when cooling Gross oversizing may also contribute tohigher energy use by increasing cyclic thermal losses and off-cyclelosses Variable-capacity equipment (heat pumps, air conditioners,and furnaces) can more closely match building loads over specificambient temperature ranges, usually reducing these losses andimproving comfort levels; in the case of heat pumps, supplementalheat needs may also be reduced

Recent trends toward tight building construction with improvedvapor retarders and low infiltration may cause high indoor humidityconditions and the buildup of indoor air contaminants in the space

Air-to-air heat-recovery equipment may be used to provide pered ventilation air to tightly constructed houses Outdoor airintakes connected to the return duct of central systems may also beused when reducing installed costs is the most important task Sim-ple exhaust systems with passive air intakes are also becoming pop-ular However, all ventilation schemes increase the building loadand the required system capacity, thereby resulting in greater energyconsumption In all cases, minimum ventilation rates, as outlined in

tem-ASHRAE Standard 62, should be maintained.

SINGLE-FAMILY RESIDENCES Heat Pumps

Heat pumps for single-family houses are normally unitary tems; that is, they use single-package units or split systems as illus-trated in Figure 2

sys-Most commercially available heat pumps (particularly in NorthAmerica) are electrically powered air-source systems Supplemen-tal heat is generally required at low outdoor temperatures or duringdefrost In most cases, supplemental or backup heat is provided byelectric resistance heaters

Heat pumps may be classified by thermal source and distributionmedium in the heating mode as well as the type of fuel used Themost commonly used classes of heat pump equipment are air-to-airand water-to-air Air-to-water and water-to-water types are also used

Heat pump systems, as contrasted to the heat pump equipment,are generally described as air-source or ground-source The thermalsink for cooling is generally assumed to be the same as the thermalsource for heating Air-source systems using ambient air as the heatsource/sink are generally the least costly to install and thus the mostcommonly used Ground-source systems usually use water-to-airheat pumps to extract heat from the ground via groundwater or aburied heat exchanger

Ground-Source (Geothermal) Systems As a heat source/sink,

groundwater (from individual wells or supplied as a utility fromcommunity wells) offers the following advantages over ambient air:

(1) heat pump capacity is independent of ambient air temperature,reducing supplementary heating requirements; (2) no defrost cycle

is required; (3) although operating conditions for establishing ratedefficiency are not the same as for air-source systems, the seasonalefficiency is usually higher for heating and for cooling; and (4) peakheating energy consumption is usually lower Two other systemtypes are ground-coupled and surface-water-coupled systems

Ground-coupled systems offer the same advantages, but becausesurface water temperatures track fluctuations in air temperature,surface-water-coupled systems may not offer the same benefits asother ground-source systems Both system types circulate brine orwater in a buried or submerged heat exchanger to transfer heat fromthe ground Direct-expansion ground-source systems, with evapo-rators buried in the ground, are rarely used Water-source systems

Fig 2 Typical Residential Installation of Heat Pump

Fig 2 Typical Residential Installation of Heat Pump

that extract heat from surface water (e.g., lakes or rivers) or city (tap)

water are sometimes used where local conditions permit

Water supply, quality, and disposal must be considered for

groundwater systems Caneta Research (1995) and Kavanaugh and

Rafferty (1997) provide detailed information on these subjects

Secondary coolants for ground-coupled systems are discussed in

Caneta Research (1995) and in Chapter 21 of the ASHRAE

Hand-book—Fundamentals Buried heat exchanger configurations may be

horizontal or vertical, with the vertical including both

multiple-shallow- and single-deep-well configurations Ground-coupled

sys-tems avoid water quality, quantity, and disposal concerns but are

sometimes more expensive than groundwater systems However,

ground-coupled systems are usually more efficient, especially when

pumping power for the groundwater system is considered Proper

installation of the ground coil(s) is critical to success

Add-On Heat Pumps In add-on systems, a heat pump is

added—often as a retrofit—to an existing furnace or boiler plus fan

coil system The heat pump and combustion device are operated in

one of two ways: (1) alternately, depending on which is most

cost-effective, or (2) in parallel In unitary bivalent heat pumps, the heat

pump and combustion device are grouped in a common chassis and

cabinets to provide similar benefits at lower installation costs

Fuel-Fired Heat Pumps Extensive research and development

has been conducted to develop fuel-fired heat pumps They have

been marketed in North America

Water-Heating Options Heat pumps may be equipped with

desuperheaters (either integral or field-installed) to reclaim heat for

domestic water heating when operated in the cooling mode

Inte-grated space-conditioning and water-heating heat pumps with an

additional full-size condenser for water heating are also available

Furnaces

Furnaces are fueled by gas (natural or propane), electricity, oil,

wood, or other combustibles Gas, oil, and wood furnaces may draw

combustion air from the house or from outdoors If the furnace space

is located such that combustion air is drawn from the outdoors, the

arrangement is called an isolated combustion system (ICS) Furnaces

are generally rated on an ICS basis When outdoor air is ducted to the

combustion chamber, the arrangement is called a direct vent system

This latter method is used for manufactured home applications and

some mid- and high-efficiency equipment designs Using outside air

for combustion eliminates both the infiltration losses associated with

the use of indoor air for combustion and the stack losses associated

with atmospherically induced draft hood-equipped furnaces

Two available types of high-efficiency gas furnaces are

noncon-densing and connoncon-densing Both increase efficiency by adding or

improving heat exchanger surface area and reducing heat loss during

furnace off-times The higher-efficiency condensing type also

recov-ers more energy by condensing water vapor from the combustion

products The condensate is developed in a high-grade stainless steel

heat exchanger and is disposed of through a drain line Condensing

furnaces generally use PVC for vent pipes and condensate drains

Wood-fueled furnaces are used in some areas A recent advance

in wood furnaces is the addition of catalytic converters to enhance

the combustion process, increasing furnace efficiency and

produc-ing cleaner exhaust

Chapters 28 and 29 of the ASHRAE Handbook—Systems and

Equipment include more detailed information on furnaces and

fur-nace efficiency

Hydronic Heating Systems

With the growth of demand for central cooling systems, hydronic

systems have declined in popularity in new construction, but still

account for a significant portion of existing systems in colder

cli-mates The fluid is heated in a central boiler and distributed by

pip-ing to terminal units in each room Terminal units are typically

either radiators or baseboard convectors Other terminal units

include fan coils and radiant panels Most recently installed tial systems use a forced-circulation, multiple-zone hot water sys-tem with a series-loop piping arrangement Chapters 12, 27, and 32

residen-of the ASHRAE Handbook—Systems and Equipment have moreinformation on hydronics

Design water temperature is based on economic and comfortconsiderations Generally, higher temperatures result in lower firstcosts because smaller terminal units are needed However, lossestend to be greater, resulting in higher operating costs and reducedcomfort due to the concentrated heat source Typical design temper-atures range from 80 to 95°C For radiant panel systems, designtemperatures range from 45 to 75°C The preferred control methodallows the water temperature to decrease as outdoor temperaturesrise Provisions for expansion and contraction of piping and heatdistributing units and for eliminating air from the hydronic systemare essential for quiet, leaktight operation

Fossil fuel systems that condense water vapor from the flue gasesmust be designed for return water temperatures in the range of 50 to55°C for most of the heating season Noncondensing systems mustmaintain high enough water temperatures in the boiler to preventthis condensation If rapid heating is required, both terminal unitand boiler size must be increased, although gross oversizing should

be avoided

Another concept for multi- or single-family dwellings is a bined water-heating/space-heating system that uses water from thedomestic hot water storage tank to provide space heating Water cir-culates from the storage tank to a hydronic coil in the system air han-dler Space heating is provided by circulating indoor air across thecoil A split-system central air conditioner with the evaporator located

com-in the system air handler can be com-included to provide space coolcom-ing

Zoned Heating Systems

Zoned systems offer the potential for lower operating costs,because unoccupied areas can be kept at lower temperatures in thewinter Common areas can be maintained at lower temperatures atnight and sleeping areas at lower temperatures during the day.One form of this system consists of individual heaters located

in each room These heaters are usually electric or gas-fired tric heaters are available in the following types: baseboard free-convection, wall insert (free-convection or forced-fan), radiantpanels for walls and ceilings, and radiant cables for walls, ceil-ings, and floors Matching equipment capacity to heating require-ments is critical for individual room systems Heating deliverycannot be adjusted by adjusting air or water flow, so greater preci-sion in room-by-room sizing is needed Most individual heatershave integral thermostats that limit the ability to optimize unitcontrol without continuous fan operation

Elec-Individual heat pumps for each room or group of rooms (zone)are another form of zoned electric heating For example, two ormore small unitary heat pumps can be installed in two-story or largeone-story homes

The multisplit heat pump consists of a central compressor and

an outdoor heat exchanger to service up to eight indoor zones.Each zone uses one or more fan coils, with separate thermostaticcontrols for each zone Such systems are used in both new and ret-rofit construction

A method for zoned heating in central ducted systems is thezone-damper system This consists of individual zone dampers andthermostats combined with a zone control system Both variable airvolume (damper position proportional to zone demand) and on-off(damper fully open or fully closed in response to thermostat) typesare available Such systems sometimes include a provision to mod-ulate to lower capacities when only a few zones require heating

Solar Heating

Both active and passive solar energy systems are sometimes used

to heat residences In typical active systems, flat plate collectors

heat air or water Air systems distribute heated air either to the living

space for immediate use or to a thermal storage medium (e.g., a rock

pile) Water systems pass heated water through a secondary heat

exchanger and store extra heat in a water tank Due to low delivered

water temperatures, radiant floor panels requiring moderate

temper-atures are generally used

Trombe walls and sunspaces are two common passive

sys-tems Glazing facing south (in the northern hemisphere), with

overhangs to reduce solar gains in the summer, and movable

insulated panels can reduce heating requirements

Some form of backup heating is generally needed with solar

energy systems

Chapter 32 has information on sizing solar heating equipment

Unitary Air Conditioners

In forced-air systems, the same air distribution duct system can

be used for both heating and cooling Split-system central cooling,

as illustrated in Figure 1, is the most widely used forced-air system

Upflow, downflow, and horizontal-airflow indoor units are

avail-able Condensing units are installed on a noncombustible pad

out-side and contain a motor- or engine-driven compressor, condenser,

condenser fan and fan motor, and controls The condensing unit and

evaporator coil are connected by refrigerant tubing that is normally

field-supplied However, precharged, factory-supplied tubing with

quick-connect couplings is also common where the distance

between components is not excessive

A distinct advantage of split-system central cooling is that it can

readily be added to existing forced-air heating systems Airflow

rates are generally set by the cooling requirements to achieve good

performance, but most existing heating duct systems are adaptable

to cooling Airflow rates of 45 to 60 L/s per kilowatt of refrigeration

are normally recommended for good cooling performance As with

heat pumps, these systems may be fitted with desuperheaters for

domestic water heating

Some cooling equipment includes forced-air heating as an integral

part of the product Year-round heating and cooling packages with a

gas, oil, or electric furnace for heating and a vapor-compression

sys-tem for cooling are available Air-to-air and water-source heat pumps

provide cooling and heating by reversing the flow of refrigerant

Distribution Duct systems for cooling (and heating) should be

designed and installed in accordance with accepted practice Useful

information is found in ACCA Manuals D and G Chapter 9 of the

ASHRAE Handbook—Systems and Equipment also discusses air

distribution design for small heating and cooling systems

Because weather is the primary influence on the load, the

cool-ing and heatcool-ing load in each room changes from hour to hour

Therefore, the owner or occupant should be able to make seasonal

or more frequent adjustments to the air distribution system to

obtain improved comfort Such adjustments may involve opening

additional outlets in second-floor rooms during the summer and

throttling or closing heating outlets in some rooms during the

win-ter Manually adjustable balancing dampers may be provided to

facilitate these adjustments Other possible refinements are the

installation of a heating and cooling system sized to meet heating

requirements, with additional self-contained cooling units serving

rooms with high summer loads, or of separate central systems for

the upper and lower floors of a house On deluxe applications,

zone-damper systems can be used Another way of balancing

cool-ing and heatcool-ing loads is by uscool-ing variable-capacity compressors in

heat pump systems

Operating characteristics of both heating and cooling equipment

must be considered when zoning is used For example, a reduction

in the air quantity to one or more rooms may reduce the airflow

across the evaporator to such a degree that frost forms on the fins

Reduced airflow on heat pumps during the heating season can cause

overloading if airflow across the indoor coil is not maintained above

45 L/s per kilowatt Reduced air volume to a given room would

reduce the air velocity from the supply outlet and might cause isfactory air distribution in the room Manufacturers of zoned sys-tems normally provide guidelines for avoiding such situations

unsat-Special Considerations In split-level houses, cooling and heating

are complicated by air circulation between various levels In manysuch houses, the upper level tends to overheat in winter and undercool

in summer Multiple outlets, some near the floor and others near theceiling, have been used with some success on all levels To control air-flow, the homeowner opens some outlets and closes others from sea-son to season Free circulation between floors can be reduced bylocating returns high in each room and keeping doors closed

In existing homes, the cooling that can be added is limited by theair-handling capacity of the existing duct system Although theexisting duct system is usually satisfactory for normal occupancy, itmay be inadequate during large gatherings In all cases where newcooling (or heating) equipment is installed in existing homes, sup-ply-air ducts and outlets must be checked for acceptable air-han-dling capacity and air distribution Maintaining upward airflow at

an effective velocity is important when converting existing heatingsystems with floor or baseboard outlets to both heat and cool It isnot necessary to change the deflection from summer to winter forregisters located at the perimeter of a residence Registers locatednear the floor on the inside walls of rooms may operate unsatisfac-torily if the deflection is not changed from summer to winter

Occupants of air-conditioned spaces usually prefer minimumperceptible air motion Perimeter baseboard outlets with multipleslots or orifices directing air upwards effectively meet this re-quirement Ceiling outlets with multidirectional vanes are alsosatisfactory

A residence without a forced-air heating system may be cooled

by one or more central systems with separate duct systems, by vidual room air conditioners (window-mounted or through-the-wall), or by minisplit room air conditioners

indi-Cooling equipment must be located carefully Because coolingsystems require higher indoor airflow rates than most heating sys-tems, the sound levels generated indoors are usually higher Thus,indoor air-handling units located near sleeping areas may requiresound attenuation Outdoor noise levels should also be consideredwhen locating the equipment Many communities have ordinancesregulating the sound level of mechanical devices, including coolingequipment Manufacturers of unitary air conditioners often certify

the sound level of their products in an ARI program (ARI Standard 270) ARI Standard 275 gives information on how to predict the

dBA sound level when the ARI sound rating number, the equipmentlocation relative to reflective surfaces, and the distance to the prop-erty line are known

An effective and inexpensive way to reduce noise is to put tance and natural barriers between sound source and listener How-ever, airflow to and from air-cooled condensing units must not beobstructed Most manufacturers provide recommendations regard-ing acceptable distances between condensing units and natural bar-riers Outdoor units should be placed as far as is practical fromporches and patios, which may be used while the house is beingcooled Locations near bedroom windows and neighboring homesshould also be avoided

dis-Evaporative Coolers

In climates that are dry throughout the entire cooling season,evaporative coolers can be used to cool residences Further details

on evaporative coolers can be found in Chapter 19 of the ASHRAE

Handbook—Systems and Equipment and in Chapter 51 of this ume

vol-Humidifiers

For improved winter comfort, equipment that increases indoorrelative humidity may be needed In a ducted heating system, a

central humidifier can be attached to or installed within a supply

plenum or main supply duct, or installed between the supply and

return duct systems When applying supply-to-return duct

humidi-fiers on heat pump systems, care should be taken to maintain proper

airflow across the indoor coil Self-contained humidifiers can be

used in any residence Even though this type of humidifier

intro-duces all the moisture to one area of the home, moisture will migrate

and raise humidity levels in other rooms

Overhumidification, which can cause condensate to form on the

coldest surfaces in the living space (usually the windows), should be

avoided Also, because moisture migrates through all structural

materials, vapor retarders should be installed near the warmer inside

surface of insulated walls, ceilings, and floors in most temperature

climates Lack of attention to this construction detail allows

mois-ture to migrate from inside to outside, causing damp insulation,

pos-sible structural damage, and exterior paint blistering

Central humidifiers may be rated in accordance with ARI

Stan-dard 610 This rating is expressed in the number of litres per day

evaporated by 60°C entering air Some manufacturers certify the

performance of their product to the ARI standard Selecting the

proper size humidifier is important and is outlined in ARI

Guide-line F.

Humidifier cleaning and maintenance schedules should be

fol-lowed to maintain efficient operation and prevent bacteria build-up

Chapter 20 of the ASHRAE Handbook—Systems and Equipment

contains more information on residential humidifiers

Dehumidifiers

Many homes also use dehumidifiers to remove moisture and

con-trol indoor humidity levels In cold climates, dehumidification is

sometimes required during the summer in basement areas to control

mold and mildew growth and to reduce zone humidity levels

Tra-ditionally, portable dehumidifiers have been used to control

humid-ity in this application Although these portable units are not always

as efficient as central systems, their low first cost and the ability to

serve a single zone make them appropriate in many circumstances

In hot and humid climates, the importance of providing sufficient

dehumidification with sensible cooling is increasingly recognized

Although conventional air conditioning units provide some

dehu-midification as a consequence of sensible cooling, in some cases

space humidity levels can still exceed the upper limit of 60%

rela-tive humidity specified in ASHRAE Standard 55.

Several dehumidification enhancements to conventional

air-conditioning systems are possible to improve moisture removal

characteristics and lower the space humidity level Some simple

improvements include lowering the supply airflow rate and

elimi-nating off-cycle fan operation Additional equipment options such

as condenser/reheat coils, sensible-heat-exchanger-assisted

evapo-rators (e.g., heat pipes), and subcooling/reheat coils can further

improve dehumidification performance Desiccants, applied as

either thermally activated units or heat recovery systems (e.g.,

enthalpy wheels), can also increase dehumidification capacity and

lower the indoor humidity level Some dehumidification options

add heat to the conditioned zone that, in some cases, increases the

load on the sensible cooling equipment

Air Filters

Most comfort conditioning systems that circulate air incorporate

some form of air filter Usually they are disposable or cleanable

filters that have relatively low air-cleaning efficiency

Higher-efficiency alternatives include pleated media filters and electronic

air filters These high-efficiency filters may have high static

pres-sure drops The air distribution system should be carefully evaluated

before installing such filters

Air filters are mounted in the return air duct or plenum and

oper-ate whenever air circuloper-ates through the duct system Air filters are

rated in accordance with ARI Standard 680, which is based on ASHRAE Standard 52.1 Atmospheric dust spot efficiency levels

are generally less than 20% for disposable filters and vary from 60

to 90% for electronic air filters

To maintain optimum performance, the collector cells of tronic air filters must be cleaned periodically Automatic indicatorsare often used to signal the need for cleaning Electronic air filtershave higher initial costs than disposable or pleated filters, but gen-erally last the life of the air-conditioning system Chapter 24 of the

elec-ASHRAE Handbook—Systems and Equipment covers the design ofresidential air filters in more detail

Controls

Historically, residential heating and cooling equipment has beencontrolled by a wall thermostat Today, simple wall thermostats withbimetallic strips are often replaced by microelectronic models thatcan set heating and cooling equipment at different temperature lev-els, depending on the time of day This has led to night setback con-trol to reduce energy demand and operating costs For heat pumpequipment, electronic thermostats can incorporate night setbackwith an appropriate scheme to limit use of resistance heat duringrecovery Chapter 45 contains more details about automatic controlsystems

MULTIFAMILY RESIDENCES

Attached homes and low-rise multifamily apartments generallyuse heating and cooling equipment comparable to that used insingle-family dwellings Separate systems for each unit allow indi-vidual control to suit the occupant and facilitate individual metering

of energy use

Forced-Air Systems

High-rise multifamily structures may also use unitary heatingand cooling equipment comparable to that used in single-familydwellings Equipment may be installed in a separate mechanicalequipment room in the apartment, or it may be placed in a soffit orabove a drop ceiling over a hallway or closet

Small residential warm-air furnaces may also be used, but ameans of providing combustion air and venting combustion prod-ucts from gas- or oil-fired furnaces is required It may be neces-sary to use a multiple-vent chimney or a manifold-type ventsystem Local codes should be consulted Direct vent furnacesthat are placed near or on an outside wall are also available forapartments

Hydronic Systems

Individual heating and cooling units are not always possible orpractical in high-rise structures In this case, applied central sys-tems are used Two- or four-pipe hydronic central systems arewidely used in high-rise apartments Each dwelling unit has eitherindividual room units or ducted fan-coil units

The most flexible hydronic system with usually the lowest ating costs is the four-pipe type, which provides heating or coolingfor each apartment dweller The two-pipe system is less flexiblebecause it cannot provide heating and cooling simultaneously Thislimitation causes problems during the spring and fall when someapartments in a complex require heating while others require cool-ing due to solar or internal loads This spring/fall problem may beovercome by operating the two-pipe system in a cooling mode andproviding the relatively low amount of heating that may be required

oper-by means of individual electric resistance heaters

See the section on Hydronic Heating Systems for description of acombined water-heating/space-heating system for multi- or single-family dwellings Chapter 12 of the ASHRAE Handbook—Systems

and Equipment discusses hydronic design in more detail

Through-the-Wall Units

Through-the-wall room air conditioners, packaged terminal air

conditioners (PTACs), and packaged terminal heat pumps (PTHPs)

can be used for conditioning single rooms Each room with an

out-side wall may have such a unit These units are used extensively in

the renovation of old buildings because they are self-contained and

typically do not require complex piping or ductwork renovation

Room air conditioners have integral controls and may include

resistance or heat pump heating PTACs and PTHPs have special

indoor and outdoor appearance treatments, making them adaptable

to a wider range of architectural needs PTACs can include gas,

elec-tric resistance, hot water, or steam heat Integral or remote

wall-mounted controls are used for both PTACs and PTHPs Further

information may be found in Chapter 46 of the ASHRAE

Hand-book—Systems and Equipment and in ARI Standard 310/380.

Water-Loop Heat Pumps

Any mid- or high-rise structure having interior zones with high

internal heat gains that require year-round cooling can efficiently

use a water-loop heat pump Such systems have the flexibility and

control of a four-pipe system while using only two pipes

Water-source heat pumps allow for individual metering of each apartment

The building owner pays only the utility cost for the circulating

pump, cooling tower, and supplemental boiler heat Existing

build-ings can be retrofitted with heat flow meters and timers on fan

motors for individual metering Economics permitting, solar or

ground heat energy can provide the supplementary heat in lieu of a

boiler The ground can also provide a heat sink, which in some cases

can eliminate the cooling tower In areas where the water table is

continuously high and the soil is porous, groundwater from wells

can be used

Special Concerns for Apartment Buildings

Many ventilation systems are used in apartment buildings

Local building codes generally govern air quantities ASHRAE

Standard 62 requires minimum outdoor air values of 24 L/s

inter-mittent or 10 L/s continuous or operable windows for baths and

toi-lets, and 48 L/s intermittent or 12 L/s continuous or operable

windows for kitchens

In some buildings with centrally controlled exhaust and supply

systems, the systems are operated on time clocks for certain periods

of the day In other cases, the outside air is reduced or shut off during

extremely cold periods If known, these factors should be

consid-ered when estimating heating load

Another important load, frequently overlooked, is heat gain from

piping for hot water services

Buildings using exhaust and supply air systems 24 h/day may

benefit from air-to-air heat recovery devices (see Chapter 44 of the

ASHRAE Handbook—Systems and Equipment) Such recovery

devices can reduce energy consumption by transferring 40 to 80%

of the sensible and latent heat between the exhaust air and supply air

streams

Infiltration loads in high-rise buildings without ventilation

open-ings for perimeter units are not controllable on a year-round basis by

general building pressurization When outer walls are pierced to

supply outdoor air to unitary or fan-coil equipment, combined wind

and thermal stack effects create other infiltration problems

Interior public corridors in apartment buildings need positive

ventilation with at least two air changes per hour Conditioned

sup-ply air is preferable Some designs transfer air into the apartments

through acoustically lined louvers to provide kitchen and toilet

makeup air, if necessary Supplying air to, instead of exhausting air

from, corridors minimizes odor migration from apartments into

corridors

Air-conditioning equipment must be isolated to reduce noise

generation or transmission The design and location of cooling

tow-ers must be chosen to avoid disturbing occupants within the buildingand neighbors in adjacent buildings Also, for cooling towers, pre-

vention of Legionella is a serious concern Further information on

cooling towers is in Chapter 36 of the ASHRAE

Handbook—Sys-tems and Equipment

In large apartment houses, a central panel may allow individualapartment air-conditioning systems or units to be monitored formaintenance and operating purposes

MANUFACTURED HOMES

Manufactured homes are constructed at a factory and in 1999constituted over 7% of all housing units and about 21% of all newsingle-family homes sold In the United States, heating and cool-ing systems in manufactured homes, as well as other facets ofconstruction such as insulation levels, are regulated by HUD Man-ufactured Home Construction and Safety Standards Each com-plete home or home section is assembled on a transportationframe—a chassis with wheels and axles—for transport Manufac-tured homes vary in size from small, single-floor section unitsstarting at 37 m2 to large, multiple sections, which when joinedtogether can provide over 230 m2 and have an appearance similar

to site-constructed homes

Heating systems are factory-installed and are primarily air downflow units feeding main supply ducts built into the subfloor,with floor registers located throughout the home A small percent-age of homes in the far South and in the Southwest use upflow unitsfeeding overhead ducts in the attic space Typically there is no returnduct system Air returns to the air handler from each room throughhallways The complete heating system is a reduced clearance typewith the air-handling unit installed in a small closet or alcove usu-ally located in a hallway Sound control measures may be required

forced-if large forced-air systems are installed close to sleeping areas Gas,oil, and electric furnaces or heat pumps may be installed by thehome manufacturer to satisfy market requirements

Gas and oil furnaces are compact direct-vent types that have beenapproved for installation in a manufactured home The special vent-ing arrangement used is a vertical through-the-roof concentric pipe-in-pipe system that draws all air for combustion directly from theoutdoors and discharges the combustion products through a wind-proof vent terminal Gas furnaces must be easily convertible fromliquefied petroleum to natural gas and back as required at the finalsite

Manufactured homes may be cooled with add-on split or package air-conditioning systems when the supply ducts are ade-quately sized and rated for that purpose according to HUD require-ments The split-system evaporator coil may be installed in theintegral coil cavity provided with the furnace A high static pressureblower is used to overcome resistance through the furnace, the evap-orator coil, and the compact air duct distribution system Single-package air conditioners are connected with flexible air ducts tofeed existing factory in-floor or overhead ducts Dampers or othermeans are required to prevent the cooled, conditioned air from back-flowing through a furnace cabinet

single-A typical installation of a downflow gas or oil furnace with asplit-system air conditioner is illustrated in Figure 3 Air enters thefurnace from the hallway (1), passing through a louvered door (2) onthe front of the furnace The air then passes through air filters (3)and is drawn into the top-mounted blower (4), which during the win-ter forces air down over the heat exchanger, where it picks up heat

For summer cooling, the blower forces air through the furnace heatexchanger and then through the split-system evaporator coil (5),which removes heat and moisture from the passing air During heat-ing and cooling, the conditioned air then passes through a combus-tible floor base via a duct connector (6) before flowing into the floorair distribution duct (7) The evaporator coil is connected via quick-connect refrigerant lines (8) to a remote air-cooled condensing unit

(9) The condensate collected at the evaporator is drained by a

flex-ible hose (10), routed to the exterior through the floor construction,

and connected to a suitable drain

REFERENCES

ACCA 1970 Selection of distribution systems Manual G, 1st ed

Air-Con-ditioning Contractors of America, Washington, D.C.

ACCA 1986 Load calculation for residential winter and summer air

condi-tioning Manual J, 7th ed Air-Conditioning Contractors of America,

Washington, D.C.

ACCA 1995 Duct design for residential winter and summer air

condition-ing and equipment selection Manual D, 3rd ed Air-Conditioncondition-ing

Con-tractors of America, Washington, D.C.

ARI 1993 Packaged terminal air-conditioners and heat pumps Standard

310/380-93 Air Conditioning and Refrigeration Institute, Arlington, VA.

ARI 1993 Residential air filter equipment Standard 680-93 Air

Condi-tioning and Refrigeration Institute, Arlington, VA.

ARI 1995 Sound rating of outdoor unitary equipment Standard 270-95.

Air Conditioning and Refrigeration Institute, Arlington, VA.

ARI 1996 Central system humidifiers for residential applications Standard

610-96 Air Conditioning and Refrigeration Institute, Arlington, VA ARI 1997 Selection, installation and servicing of residential humidifiers.

Guideline F-1997 Air Conditioning and Refrigeration Institute,

Arling-ton, VA.

ARI 1997 Application of sound rating levels of outdoor unitary equipment.

Standard 275-97 Air Conditioning and Refrigeration Institute,

Kavanaugh, S.P and K Rafferty 1997 Ground source heat pumps—Design

of geothermal systems for commercial and institutional buildings.

ASHRAE.

Fig 3 Typical Installation of Heating and Cooling

Equip-ment for a Manufactured Home

Fig 3 Typical Installation of Heating and Cooling

Equipment for a Manufactured Home

HIS chapter covers design and application of air-conditioning

Tand heating systems for various retail merchandising facilities

Load calculations, systems, and equipment are covered elsewhere in

the Handbook series

GENERAL CRITERIA

To apply equipment properly, the construction of the space to be

conditioned, its use and occupancy, the time of day in which greatest

occupancy occurs, physical building characteristics, and lighting

layout must be known

The following must also be considered:

• Electric power—size of service

• Heating—availability of steam, hot water, gas, oil, or electricity

• Cooling—availability of chilled water, well water, city water, and

water conservation equipment

• Internal heat gains

• Rigging and delivery of equipment

• Structural considerations

• Obstructions

• Ventilation—opening through roof or wall for outside air duct,

number of doors to sales area, and exposures

• Orientation of store

• Code requirements

• Utility rates and regulations

• Building standards

Specific design requirements, such as the increase in outside air

required for exhaust where lunch counters exist, must be

consid-ered The requirements of ASHRAE ventilation standards must be

followed Heavy smoking and objectionable odors may necessitate

special filtering in conjunction with outside air intake and exhaust

Load calculations should be made using the procedure outlined in

Chapter 29 of the ASHRAE Handbook—Fundamentals

Almost all localities have some form of energy code in effect that

establishes strict requirements for insulation, equipment

efficien-cies, system designs, etc., and places strict limits on fenestration and

lighting The requirements of ASHRAE Standard 90 should be met

as a minimum guideline for retail facilities

HVAC system selection and design for retail facilities are

nor-mally determined by economics First cost is usually the

determin-ing factor for small stores; for large retail facilities, operatdetermin-ing and

maintenance costs are also considered Generally, decisions about

mechanical systems for retail facilities are based on a cash flow

analysis rather than on a full life-cycle analysis

SMALL STORES

Large glass areas found at the front of many small stores may

cause high peak solar heat gain unless they have northern exposures

High heat loss may be experienced on cold, cloudy days The HVAC

system for this portion of the small store should be designed to

offset the greater cooling and heating requirements Entrance bules and heaters may be needed in cold climates

vesti-Many new small stores are part of a shopping center Althoughexterior loads will differ between stores, internal loads will be sim-ilar; proper design is important

Design Considerations

System Design Single-zone unitary rooftop equipment is

com-mon in store air conditioning Using multiple units to condition thestore involves less ductwork and can maintain comfort in the event

of partial equipment failure Prefabricated and matching curbs plify installation and ensure compatibility with roof materials.Heat pumps, offered as packaged equipment, are readily adapt-able to small-store applications and have a low first cost Winterdesign conditions, utility rates, and operating cost should be com-pared to those for conventional heating systems before this type ofequipment is chosen

sim-Water-cooled unitary equipment is available for small-store airconditioning, but many U.S communities restrict the use of citywater and groundwater for condensing purposes and require instal-lation of a cooling tower Water-cooled equipment generally oper-ates efficiently and economically

Retail facilities often have a high sensible heat gain relative to thetotal heat gain Unitary HVAC equipment should be designed andselected to provide the necessary sensible heat removal

Air Distribution External static pressures available in

small-store air-conditioning units are limited, and ducts should bedesigned to keep duct resistances low Duct velocities should notexceed 6 m/s and pressure drop should not exceed 0.8 Pa/m.Average air quantities range from 47 to 60 L/s per kilowatt ofcooling in accordance with the calculated internal sensible heatload

Attention should be paid to suspended obstacles, such as lightsand displays, that interfere with proper air distribution

The duct system should contain enough dampers for air ing Dampers should be installed in the return and outside air ductfor proper outside air/return air balance Volume dampers should beinstalled in takeoffs from the main supply duct to balance air to thebranch ducts

balanc-Control Controls for small stores should be kept as simple as

possible while still able to perform required functions Unitaryequipment is typically available with manufacturer-supplied con-trols for easy installation and operation

Automatic dampers should be placed in the outside air intake toprevent outside air from entering when the fan is turned off.Heating controls vary with the nature of the heating medium.Duct heaters are generally furnished with manufacturer-installedsafety controls Steam or hot-water heating coils require a motor-ized valve for heating control

Time clock control can limit unnecessary HVAC operation.Unoccupied reset controls should be provided in conjunction withtimed control

Maintenance To protect the initial investment and ensure

max-imum efficiency, maintenance of air-conditioning units in small

The preparation of this chapter is assigned to TC 9.8, Large Building

Air-Conditioning Applications.

Copyright © 2003, ASHRAE

stores should be contracted out to a reliable service company on a

yearly basis The contract should clearly specify responsibility for

filter replacements, lubrication, belts, coil cleaning, adjustment of

controls, compressor maintenance, replacement of refrigerant,

pump repairs, electrical maintenance, winterizing, system start-up,

and extra labor required for repairs

Improving Operating Cost Outside air economizers can

re-duce the operating cost of cooling in most climates They are

gen-erally available as factory options or accessories with roof-mounted

units Increased exterior insulation generally reduces operating

en-ergy requirements and may in some cases allow the size of installed

equipment to be reduced Many codes now include minimum

re-quirements for insulation and fenestration materials

DISCOUNT, BIG-BOX, AND

SUPERCENTER STORES

Large warehouse or big-box stores attract customers with

dis-count prices when large quantities are purchased These stores

typ-ically have high-bay fixture displays and usually store merchandise

in the sales area They feature a wide range of merchandise and may

include such diverse areas as a lunch counter, an auto service area,

a supermarket, a pharmacy, and a garden shop Some stores sell

pets, including fish and birds This variety of merchandise must be

considered in designing air conditioning The design and

applica-tion suggesapplica-tions for small stores also apply to discount stores

Another type of big-box facility provides both dry good and

grocery areas The grocery area is typically treated as a traditional

stand-alone grocery (see the section on Supermarkets)

Condition-ing outside air for the dry goods areas must be considered to limit

the introduction of excess moisture that will migrate to the freezer

aisles

Hardware, lumber, furniture, etc., is also sold in big-box

facili-ties A particular concern in this type of facility is ventilation for

material-handling equipment, such as forklift trucks

In addition, areas such as stockrooms, rest rooms, offices, and

special storage rooms for perishable merchandise may require air

conditioning or refrigeration

Load Determination

Operating economics and the spaces served often dictate inside

design conditions Some stores may base summer load calculations

on a higher inside temperature (e.g., 27ºC db) but then set the

ther-mostats to control at 22 to 24ºC db This reduces the installed

equip-ment size while providing the desired inside temperature most of the

time

Special rooms for storage of perishable goods are usually

designed with separate unitary air conditioners

The heat gain from lighting will not be uniform throughout the

entire area For example, jewelry and other specialty displays

typi-cally have lighting heat gains of 65 to 85 W per square meter of floor

area, whereas the typical sales area has an average value of 20 to

40 W/m2 For stockrooms and receiving, marking, toilet, and rest

room areas, a value of 20 W/m2 may be used When available, actual

lighting layouts rather than average values should be used for load

computation

The store owner usually determines the population density for a

store based on its location, size, and past experience

Food preparation and service areas in discount and outlet stores

range from small lunch counters with heat-producing equipment

(ranges, griddles, ovens, coffee urns, toasters) in the conditioned

space to large deluxe installations with kitchens separate from the

conditioned space Chapter 31 has specific information on HVAC

systems for kitchen and eating spaces

Data on the heat released by special merchandising equipment,

such as amusement rides for children or equipment used for

pre-paring speciality food items (e.g., popcorn, pizza, frankfurters,

hamburgers, doughnuts, roasted chickens, cooked nuts, etc.), should

be obtained from the equipment manufacturers

Ventilation and outside air must be provided as required in

ASHRAE Standard 62 and local codes.

Design Considerations

Heat released by installed lighting is usually sufficient to set the design roof heat loss Therefore, interior areas of thesestores need cooling during business hours throughout the year

off-Perimeter areas, especially the storefront and entrance areas, mayhave highly variable heating and cooling requirements Properzone control and HVAC design are essential The location ofcheckout lanes in this area makes proper environmental controleven more important

System Design The important factors in selecting discount and

outlet store air-conditioning systems are (1) installation costs, (2)floor space required for equipment, (3) maintenance requirementsand equipment reliability, and (4) simplicity of control Roof-mounted units are most commonly used

Air Distribution The air supply for large sales areas should

generally be designed to satisfy the primary cooling requirement

For perimeter areas, the variable heating and cooling requirementsmust be considered

Because these stores require high, clear areas for display andrestocking, air is generally distributed from heights of 4.3 m andgreater Air distribution at these heights requires high velocities inthe heating season to overcome the buoyancy of hot air The dis-charge air velocity creates turbulence in the space and induces air-flow from the ceiling area to promote complete mixing of the air

During the cooling season the designer can take advantage ofstratification to reduce equipment load By introducing air near cus-tomers at low velocity, the air will stratify during the cooling season

With this method of air distribution, the set-point temperature can

be maintained in the occupant zone and the temperature in the upperspace can be allowed to rise However, this strategy requires equip-ment to destratify the air during the heating season Space-mountedfans, and radiant heating at the perimeter, entrance, and sales areasmay be required

Control Because the controls are usually operated by

person-nel who have little knowledge of air conditioning, systems should

be simple, dependable, and fully automatic, as simple to operate as

a residential system Most unitary equipment has automatic tronic controls for ease of operation

elec-Maintenance Most stores do not employ trained maintenance

personnel; they rely instead on service contracts with either theinstaller or a local service company For suggestions on loweringoperating costs, see the section on Small Stores

SUPERMARKETS Load Determination

Heating and cooling loads should be calculated using the ods outlined in Chapter 29 of the ASHRAE Handbook—Fundamen-

meth-tals Data for calculating loads caused by people, lights, motors, andheat-producing equipment should be obtained from the store owner

or manager or from the equipment manufacturer In supermarkets,space conditioning is required both for human comfort and forproper operation of refrigerated display cases The air-conditioningunit should introduce a minimum quantity of outside air, either the

volume required for ventilation based on ASHRAE Standard 62 or

the volume required to maintain slightly positive pressure in thespace, whichever is larger

Many supermarkets are units of a large chain owned or operated

by a single company The standardized construction, layout, andequipment used in designing many similar stores simplify loadcalculations

It is important that the final air-conditioning load be correctly

determined Refer to manufacturers’ data for information on total

heat extraction, sensible heat, latent heat, and percentage of latent to

total loadfor display cases Engineers report considerable fixture

heat removal (case load) variation as the relative humidity and

temperature vary in comparatively small increments Relative

humidity above 55% (24°C and 10.3 g/kg absolute humidity)

sub-stantially increases the load; reduced absolute humidity

substan-tially decreases the load, as shown in Figure 1 Trends in store

design, which include more food refrigeration and more efficient

lighting, reduce the sensible component of the load even further

To calculate the total load and percentage of latent and sensible

heat that the air conditioning must handle, the refrigerating effect

imposed by the display fixtures must be subtracted from the

build-ing’s gross air-conditioning requirements (Table 1)

Modern supermarket designs have a high percentage of closed

refrigerated display fixtures These vertical cases have large glass

display doors and greatly reduce the problem of latent and sensible

heat removal from the occupied space The doors do, however,

require heaters to minimize condensation and fogging These

heat-ers should cycle by automatic control

For more information on supermarkets, see Chapter 47, Retail

Food Store Refrigeration and Equipment, in the ASHRAE

Hand-book—Refrigeration

Design Considerations

Store owners and operators frequently complain about cold

aisles, heaters that operate even when the outside temperature is

above 21ºC, and air conditioners that operate infrequently These

problems are usually attributed to spillover of cold air from open

refrigerated display equipment

Although refrigerated display equipment may cause cold stores,

the problem is not excessive spillover or improperly operating

equipment Heating and air-conditioning systems must compensate

for the effects of open refrigerated display equipment Design

con-siderations include the following:

• Increased heating requirement because of removal of large

quan-tities of heat, even in summer

• Net air-conditioning load after deducting the latent and sensiblerefrigeration effect The load reduction and change in sensible-latent load ratio have a major effect on equipment selection

• Need for special air circulation and distribution to offset the heatremoved by open refrigerating equipment

• Need for independent temperature and humidity control.Each of these problems is present to some degree in every super-market, although situations vary with climate and store layout.Methods of overcoming these problems are discussed in the follow-ing sections Energy costs may be extremely high if the year-roundair-conditioning system has not been designed to compensate forthe effects of refrigerated display equipment

Heat Removed by Refrigerated Displays The display

refrig-erator not only cools a displayed product but envelops it in a blanket

of cold air that absorbs heat from the room air in contact with it.Approximately 80 to 90% of the heat removed from the room byvertical refrigerators is absorbed through the display opening Thus,the open refrigerator acts as a large air cooler, absorbing heat fromthe room and rejecting it via the condensers outside the building.Occasionally, this conditioning effect can be greater than the designair-conditioning capacity of the store The heat removed by the

refrigeration equipment must be considered in the design of the

air-conditioning and heating systems because this heat is beingremoved constantly, day and night, summer and winter, regardless

of the store temperature

Display cases increase the building heating requirement suchthat heat is often required at unexpected times The followingexample illustrates the extent of this cooling effect The desiredstore temperature is 24ºC Store heat loss or gain is assumed to be

8 kW/ºC of temperature difference between outside and storetemperature (This value varies with store size, location, andexposure.) The heat removed by refrigeration equipment is

56 kW (This value varies with the number of refrigerators.) Thelatent heat removed is assumed to be 19% of the total, leaving81% or 45.4 kW sensible heat removed, which will cool the store45.4/8 = 5.7ºC By constantly removing sensible heat from its

Fig 1 Refrigerated Case Load Variation with Store

Air Humidity

Fig 1 Refrigerated Case Load Variation with Store

Air Humidity

Refrigerated Display Fixtures

Display Fixture Types

RE on Building Per Unit Length of Fixture* Latent

Heat, W/m

% Latent

to Total RE

Sensible Heat, W/m

Total RE, W/m

Low-temperature (frozen food)

environment, the refrigeration equipment in this store will cool

the store 5.7ºC below outside temperature in winter and in

sum-mer Thus, in mild climates, heat must be added to the store to

maintain comfort conditions

The designer can either discard or reclaim the heat removed by

refrigeration If economics and store heat data indicate that the heat

should be discarded, heat extraction from the space must be

included in the heating load calculation If this internal heat loss is

not included, the heating system may not have sufficient capacity to

maintain design temperature under peak conditions

The additional sensible heat removed by the cases may change

the air-conditioning latent load ratio from 32% to as much as 50%

of the net heat load Removing a 50% latent load by refrigeration

alone is very difficult Normally, it requires specially designed

equipment with reheat or chemical adsorption

Multishelf refrigerated display equipment requires 55% rh or

less In the dry-bulb temperature ranges of average stores, humidity

in excess of 55% can cause heavy coil frosting, product zone

frost-ing in low-temperature cases, fixture sweatfrost-ing, and substantially

increased refrigeration power consumption

A humidistat can be used during summer cooling to control

humidity by transferring heat from the condenser to a heating coil in

the airstream The store thermostat maintains proper summer

tem-perature conditions Override controls prevent conflict between the

humidistat and the thermostat

The equivalent result can be accomplished with a conventional

air-conditioning system by using three- or four-way valves and

reheat condensers in the ducts This system borrows heat from the

standard condenser and is controlled by a humidistat For higher

energy efficiency, specially designed equipment should be

consid-ered Desiccant dehumidifiers and heat pipes have also been used

Humidity Cooling from refrigeration equipment does not

pre-clude the need for air conditioning On the contrary, it increases the

need for humidity control

With increases in store humidity, heavier loads are imposed on

the refrigeration equipment, operating costs rise, more defrost

peri-ods are required, and the display life of products is shortened The

dew point rises with relative humidity, and sweating can become so

profuse that even nonrefrigerated items such as shelving

superstruc-tures, canned products, mirrors, and walls may sweat

Lower humidity results in lower operating costs for refrigerated

cases There are three methods to reduce the humidity level: (1)

standard air conditioning, which may overcool the space when the

latent load is high and sensible load is low; (2) mechanical

dehu-midification, which removes moisture by lowering the air

tempera-ture to its dew point, and uses hot-gas reheat when needed to

discharge at any desired temperature; and (3) desiccant

dehumidifi-cation, which removes moisture independent of temperature,

sup-plying warm air to the space unless postcooling is provided to

discharge at any desired temperature

Each method provides different dew-point temperatures at

dif-ferent energy consumption and capital expenditures The designer

should evaluate and consider all consequential tradeoffs Standard

air conditioning requires no additional investment but reduces the

space dew-point temperature only to 16 to 18°C At 24°C space

temperature this results in 60 to 70% rh at best Mechanical

dehu-midifiers can provide humidity levels of 40 to 50% at 24°C Supply

air temperature can be controlled with hot-gas reheat between 10

and 32°C Desiccant dehumidification can provide levels of 35 to

40% rh at 24°C Postcooling supply air may be required, depending

on internal sensible loads A desiccant is reactivated by passing hot

air at 80 to 121ºC through the desiccant base

System Design The same air-handling equipment and

distri-bution system are generally used for both cooling and heating

The entrance area is the most difficult section to heat Many

supermarkets in the northern United States are built with

vesti-bules provided with separate heating equipment to temper the

cold air entering from outside Auxiliary heat may also be vided at the checkout area, which is usually close to the frontentrance Methods of heating entrance areas include the use of(1) air curtains, (2) gas-fired or electric infrared radiant heaters,and (3) waste heat from the refrigeration condensers

pro-Air-cooled condensing units are the most commonly used insupermarkets Typically, a central air handler conditions theentire sales area Specialty areas like bakeries, computer rooms,

or warehouses are better served with a separate air handlerbecause the loads in these areas vary and require different controlthan the sales area

Most installations are made on the roof of the supermarket

If air-cooled condensers are located on the ground outside thestore, they must be protected against vandalism as well as truckand customer traffic If water-cooled condensers are used on theair-conditioning equipment and a cooling tower is required,provisions should be made to prevent freezing during winteroperation

Air Distribution Designers overcome the concentrated load at

the front of a supermarket by discharging a large portion of thetotal air supply into the front third of the sales area

The air supply to the space with a standard air-conditioningsystem is typically 5 L/s per square metre of sales area This valueshould be calculated based on the sensible and latent internalloads The desiccant system typically requires less air supplybecause of its high moisture removal rate, typically 2.5 L/s persquare metre Mechanical dehumidification can fall within theseparameters, depending on required dew point and suction pressurelimitations

Being denser, air cooled by the refrigerators settles to the floorand becomes increasingly colder, especially in the first 900 mmabove the floor If this cold air remains still, it causes discomfortand does not help to cool other areas of the store that need morecooling Cold floors or areas in the store cannot be eliminated bythe simple addition of heat Reduction of air-conditioning capac-ity without circulation of localized cold air is analogous toinstalling an air conditioner without a fan To take advantage ofthe cooling effect of the refrigerators and provide an even tem-perature in the store, the cold air must be mixed with the generalstore air

To accomplish the necessary mixing, air returns should belocated at floor level; they should also be strategically placed toremove the cold air near concentrations of refrigerated fixtures

Returns should be designed and located to avoid creating drafts

There are two general solutions to this problem:

• Return Ducts in Floor This is the preferred method and can be

accomplished in two ways The floor area in front of the ated display cases is the coolest area Refrigerant lines are run toall of these cases, usually in tubes or trenches If the trenches ortubes are enlarged and made to open under the cases for air return,air can be drawn in from the cold area (Figure 2) The air isreturned to the air-handling unit through a tee connection to thetrench before it enters the back room area The opening throughwhich the refrigerant lines enter the back room should be sealed

refriger-If refrigerant line conduits are not used, air can be returnedthrough inexpensive underfloor ducts If refrigerators haveinsufficient undercase air passage, the manufacturer should beconsulted Often they can be raised off the floor approximately

40 mm Floor trenches can also be used as ducts for tubing,electrical supply, and so forth

Floor-level return relieves the problem of localized cold areasand cold aisles and uses the cooling effect for store cooling, orincreases the heating efficiency by distributing the air to areasthat need it most

• Fans Behind Cases If ducts cannot be placed in the floor,

circulating fans can draw air from the floor and discharge it above

the cases (Figure 3) Although this approach prevents

objection-able cold aisles in front of the refrigerated display cases, it does

not prevent an area with a concentration of refrigerated fixtures

from remaining colder than the rest of the store

Control Store personnel should only be required to change the

position of a selector switch to start or stop the system or to change

from heating to cooling or from cooling to heating Control systems

for heat recovery applications are more complex and should becoordinated with the equipment manufacturer

Maintenance and Heat Reclamation Most supermarkets,

except large chains, do not employ trained maintenance personnel,but rather rely on service contracts with either the installer or a localservice company This relieves store management of the responsi-bility of keeping the air conditioning operating properly

Heat extracted from the store and heat of compression may bereclaimed for heating cost saving One method of reclaimingrejected heat is to use a separate condenser coil located in the airconditioner’s air handler, either alternately or in conjunction withthe main refrigeration condensers, to provide heat as required (Fig-ure 4) Another system uses water-cooled condensers and deliversits rejected heat to a water coil in the air handler

The heat rejected by conventional machines using air-cooledcondensers may be reclaimed by proper duct and damper design(Figure 5) Automatic controls can either reject this heat to the out-side or recirculate it through the store

DEPARTMENT STORES

Department stores vary in size, type, and location, so tioning design should be specific to each store An ample mini-mum quantity of outside air reduces or eliminates odor problems.Essential features of a quality system include (1) an automatic con-trol system properly designed to compensate for load fluctuations,(2) zoned air distribution to maintain uniform conditions undershifting loads, and (3) use of outside air for cooling during inter-mediate seasons and peak sales periods It is also desirable toadjust inside temperature for variations in the outside temperature.Although close control of humidity is not necessary, a properlydesigned system should operate to maintain relative humidity at50% or below with a corresponding dry-bulb temperature of 26ºC.This humidity limit eliminates musty odors and retards perspira-tion, particularly in fitting rooms

The number of customers and store personnel normally found

on each conditioned floor must be ascertained, particularly in cialty departments or other areas having a greater-than-averageconcentration of occupants Lights should be checked for wattageand type Table 2 gives approximate values for lighting in variousareas; Table 3 gives approximate occupancies

spe-Fig 2 Floor Return Ducts

Fig 3 Air Mixing Using Fans Behind Cases

Fig 4 Heat Reclaiming Systems

Fig 5 Machine Room with Automatic Temperature trol Interlocked with Store Temperature Control

Control Interlocked with Store Temperature Control

Other loads, such as those from motors, beauty parlor and

restau-rant equipment, and any special display or merchandising

equip-ment, should be determined

The minimum outside air requirement should be as defined in

ASHRAE Standard 62, which is generally acceptable and adequate

for removing odors and keeping thebuilding atmosphere fresh

However, local ventilation ordinances may require greater

quanti-ties of outside air

Paint shops, alteration rooms, rest rooms, eating places, and

locker rooms should be provided with positive exhaust ventilation,

and their requirements must be checked against local codes

Design Considerations

Before performing load calculations, the designer should

exam-ine the store arrangement to determexam-ine what will affect the load and

the system design For existing buildings, actual construction, floor

arrangement, and load sources can be surveyed For new buildings,

examination of the drawings and discussion with the architect or

owner is required

Larger stores may contain beauty parlors, restaurants, lunch

counters, or auditoriums These special areas may operate during all

store hours If one of these areas has a load that is small in

propor-tion to the total load, the load may be met by the porpropor-tion of the air

conditioning serving that floor If present or future operation could

for any reason be compromised by such a strategy, this space should

be served by separate air conditioning Because of the concentrated

load in the beauty parlor, separate air distribution should be

pro-vided for this area

The restaurant, because of its required service facilities, is

gen-erally centrally located It is often used only during lunchtime For

odor control, a separate air-handling system should be considered

Future plans for the store must be ascertained because they can

have a great effect on the type of air conditioning and refrigeration

to be used

System Design Air conditioning for department stores may be

unitary or central station Selection should be based on owning and

operating costs as well as special considerations for the particular

store, such as store hours, load variations, and size of load

Large department stores often use central-station systems

con-sisting of air-handling units having chilled-water cooling coils,

hot-water heating coils, fans, and filters Air systems must have

adequate zoning for varying loads, occupancy, and usage Wide

variations in people loads may justify considering variable-volume

air distribution systems Water chilling and heating plants distribute

water to the various air handlers and zones and may take advantage

of some load diversity throughout the building

Air-conditioning equipment should not be placed in the sales

area; instead, it should be located in ceiling, roof, and mechanical

equipment room areas whenever practicable Maintenance and

operation after installation should be considered when sitingequipment

Air Distribution All buildings must be studied for

orienta-tion, wind exposure, construcorienta-tion, and floor arrangement Thesefactors affect not only load calculations, but also zone arrange-ments and duct locations In addition to entrances, wall areas withsignificant glass, roof areas, and population densities, theexpected locations of various departments (e.g., the lamp depart-ment) should be considered Flexibility must be left in the ductdesign to allow for future movement of departments The prelimi-nary duct layout should also be checked in regard to winter heat-ing to determine any special situations It is usually necessary todesign separate air systems for entrances, particularly in northernareas This is also true for storage areas where cooling is not con-templated

Air curtains may be installed at entrance doorways to limit orprevent infiltration of unconditioned air, at the same time providinggreater ease of entry compared to a vestibule with a second set ofdoors

Control The necessary extent of automatic control depends on

the type of installation and the extent to which it is zoned Controlmust be such that correctly conditioned air is delivered to each zone

Outside air intake should be automatically controlled to operate atminimum cost while providing required airflow Partial or full auto-matic control should be provided for cooling to compensate for loadfluctuations Completely automatic refrigeration plants should beconsidered

Maintenance Most department stores employ personnel for

routine operation and maintenance, but rely on service and tive maintenance contracts for refrigeration cycles, chemical treat-ment, central plant systems, and major repairs

preven-Improving Operating Cost An outside air economizer can

reduce the operating cost of cooling in most climates These aregenerally available as factory options or accessories with the air-handling units or control systems Heat recovery and thermal stor-age should also be analyzed

CONVENIENCE CENTERS

Many small stores, discount stores, supermarkets, drugstores,theaters, and even department stores are located in conveniencecenters The space for an individual store is usually leased Ar-rangements for installing air conditioning in leased space vary

Typically, the developer builds a shell structure and provides thetenant with an allowance for usual heating and cooling and otherminimum interior finish work The tenant must then install anHVAC system In another arrangement, developers install HVACunits in the small stores with the shell construction, often before thespace is leased or the occupancy is known Larger stores typicallyprovide their own HVAC design and installation

Design Considerations

The developer or owner may establish standards for typical ing and cooling that may or may not be sufficient for the tenant’sspecific requirements The tenant may therefore have to install sys-tems of different sizes and types than originally allowed for by thedeveloper The tenant must ascertain that power and other serviceswill be available for the total intended requirements

heat-The use of party walls in convenience centers tends to reduceheating and cooling loads However, the effect an unoccupied adja-cent space has on the partition load must be considered

REGIONAL SHOPPING CENTERS

Regional shopping centers generally incorporate an enclosed,heated and air-conditioned mall These centers are normally owned

by a developer, who may be an independent party, a financial tution, or one of the major tenants in the center

Major department stores are typically considered separate

build-ings, although they are attached to the mall The space for individual

small stores is usually leased Arrangements for installing air

con-ditioning in the individually leased spaces vary, but are similar to

those for small stores in convenience centers

Table 4 presents typical data that can be used as check figures and

field estimates However, this table should not be used for final

determination of load, because the values are only averages

Design Considerations

The owner provides the air-conditioning system for the

enclosed mall The mall may use a central plant or unitary

equip-ment The owner generally requires that the individual tenant

stores connect to a central plant and includes charges for heating

and cooling in the rent Where unitary systems are used, the

owner generally requires that the individual tenant install a

uni-tary system of similar design

The owner may establish standards for typical heating and

cool-ing systems that may or may not be sufficient for the tenant’s

spe-cific requirements Therefore, the tenant may have to install systems

of different sizes than originally allowed for by the developer

Leasing arrangements may include provisions that have a

det-rimental effect on conservation (such as allowing excessive

light-ing and outside air or deletlight-ing requirements for economizer

systems) The designer of HVAC for tenants in a shopping center

must be well aware of the lease requirements and work closely

with leasing agents to guide these systems toward better energy

efficiency

Many regional shopping centers contain specialty food court

areas that require special considerations for odor control, outside air

requirements, kitchen exhaust, heat removal, and refrigeration

equipment

System Design Regional shopping centers vary widely in

phys-ical arrangement and architectural design Single-level and smaller

centers usually use unitary systems for mall and tenant air

condi-tioning; multilevel and larger centers usually use a central plant The

owner sets the design of the mall and generally requires that similar

systems be installed for tenant stores

A typical central plant may distribute chilled air to individual

tenant stores and to the mall air-conditioning system and use

variable-volume control and electric heating at the local use point

Some plants distribute both hot and chilled water Some all-air

sys-tems also distribute heated air The central plant provides improved

efficiency and better overall economics of operation Central plants

also provide the basic components required for smoke control

Air Distribution Air distribution for individual stores should be

designed for a particular space occupancy Some tenant stores tain a negative pressure relative to the mall for odor control.Air distribution should maintain a slight positive pressure rela-tive to atmospheric pressure and a neutral pressure relative to most

main-of the individual tenant stores Exterior entrances should have tibules with independent heating systems

ves-Smoke management is required by many building codes, so airdistribution should be designed to easily accommodate smoke con-trol requirements

Maintenance Methods for ensuring the operation and

mainte-nance of HVAC systems in regional shopping centers are similar tothose used in department stores Individual tenant stores may have

to provide their own maintenance

Improving Operating Cost Methods for lowering operating

costs in shopping centers are similar to those used in departmentstores Some shopping centers have successfully used cooling towerheat exchanger economizers

Central plant systems for regional shopping centers typicallyhave much lower operating costs than unitary systems However, theinitial cost of the central plant system is typically higher

MULTIPLE-USE COMPLEXES

Multiple-use complexes are being developed in most metropolitanareas These complexes generally combine retail facilities with otherfacilities such as offices, hotels, residences, or other commercial spaceinto a single site This consolidation of facilities into a single site orstructure provides benefits such as improved land use; structural sav-ings; more efficient parking; utility savings; and opportunities formore efficient electrical, fire protection, and mechanical systems

Load Determination

The various occupancies may have peak HVAC demands thatoccur at different times of the day or even of the year Therefore, theHVAC loads of these occupancies should be determined indepen-dently Where a combined central plant is considered, a block loadshould also be determined

Design Considerations

Retail facilities are generally located on the lower levels ofmultiple-use complexes, and other commercial facilities are onupper levels Generally, the perimeter loads of the retail portiondiffer from those of the other commercial spaces Greater light-ing and population densities also make HVAC demands for theretail space different from those for the other commercial space.The differences in HVAC characteristics for various occupancieswithin a multiple-use complex indicate that separate air handling anddistribution should be used for the separate spaces However, com-bining the heating and cooling requirements of various facilities into

a central plant can achieve a substantial saving A combined centralheating and cooling plant for a multiple-use complex also providesgood opportunities for heat recovery, thermal storage, and other sim-ilar functions that may not be economical in a single-use facility.Many multiple-use complexes have atriums The stack effect cre-ated by atriums requires special design considerations for tenants andspace on the main floor Areas near entrances require special mea-sures to prevent drafts and accommodate extra heating requirements

System Design Individual air-handling and distribution systems

should be designed for the various occupancies The central heatingand cooling plant may be sized for the block load requirements,which may be less than the sum of each occupancy’s demand

Control Multiple-use complexes typically require centralized

control It may be dictated by requirements for fire and smoke trol, security, remote monitoring, billing for central facilities use,maintenance control, building operations control, and energy man-agement

con-Table 4 Typical Installed Cooling Capacity

and Lighting Levels—Midwestern United States

Type of Space

Area per Unit of Installed Cooling

m 2 /kW

Installed Cooling per Unit

of Area, W/m 2

Lighting Density

of Area, W/m 2

Annual Lighting Energy Use, a kWh/m 2

Fast food

food court tenant area 4.23 236.6 32.3 131.3

food court seating area 3.88 258.7 32.3 131.3

Source: Based on 2001 Data—Midwestern United States.

a Hours of operating lighting assumes 12 h/day and 6.5 days/week.

b Jewelry, high-end lingerie, and some other lighting levels are typically 65 to 85 120

W/m 2 and can range to 120 W/m 2

c 62.4 kWh/m 2 for centers that shut off lighting during daylight, assuming 6 h/day and

6.2 days/week.

HIS chapter summarizes load characteristics and both general

Tand specific design criteria that apply to commercial buildings

Design criteria include such factors as comfort level; cost; and fire,

smoke, and odor control Specific information is included on dining

and entertainment centers, office buildings, bowling centers,

com-munication centers, transportation centers, and warehouses

Muse-ums, libraries, and archives are covered in Chapter 21

GENERAL CRITERIA

In theory, most systems, if properly applied, can be successful in

any building However, in practice, such factors as initial and

oper-ating costs, space allocation, architectural design, location, and the

engineer’s evaluation and experience limit the proper choices for a

given building type

Heating and air-conditioning systems that are simple in design

and of the proper size for a given building generally have fairly low

maintenance and operating costs For optimum results, as much

inherent thermal control as is economically possible should be built

into the basic structure The relationship between the shape,

orien-tation, and air-conditioning capacity of a building should also be

considered Because the exterior load may vary from 30 to 60% of

the total air-conditioning load when the fenestration area ranges

from 25 to 75% of the exterior envelope surface area, it may be

desirable to minimize the perimeter area For example, a rectangular

building with a four-to-one aspect ratio requires substantially more

refrigeration than a square building with the same floor area

Building size, shape, and component selection are normally

determined by the building architect and/or owner Changing any of

these parameters to reach optimum results requires cooperation

among these individuals or groups

Proper design also considers controlling noise and minimizing

pollution of the atmosphere and water systems around the building

Retrofitting existing buildings is also an important part of the

construction industry because of increased costs of construction

and the necessity of reducing energy consumption Table 1 lists

factors to consider before selecting a system for any building The

selection is often made by the owner and may not be based on an

engineering study To a great degree, system selection is based on

the engineer’s ability to relate factors involving higher first cost or

lower life-cycle cost and benefits that have no calculable monetary

value

Some buildings are constructed with only heating and ventilating

systems For these buildings, greater design emphasis should be

placed on natural or forced ventilation systems to minimize

occu-pant discomfort during hot weather To provide for future cooling,

humidification, or both, the design principles are the same as those

for a fully air-conditioned building

Load Characteristics

Load characteristics for the building must be understood toensure that systems respond adequately at part load as well as atfull load Systems must be capable of responding to load fluctua-tions based on the combination of occupancy variations, processload shifts, solar load variations, and atmospheric weather condi-tions (e.g., temperature and humidity changes) Some buildingloads may be brief and infrequent, such as an annual meeting of alarge group in a conference room, whereas others may be moreconstant and long-lasting, such as operation of data processingequipment

Analysis of any building for heat recovery or total energy tems requires sufficient load profile and load duration information

sys-on all forms of building input to (1) properly evaluate the neous effect of one on the other when no energy storage is contem-plated and (2) evaluate short-term effects (up to 48 h) when energystorage is used

instanta-Load profile curves consist of appropriate energy loads plottedagainst the time of day Load duration curves indicate the accumu-lated number of hours at each load condition, from the highest to thelowest load for a day, a month, or a year The area under load profileand load duration curves for corresponding periods is equivalent tothe load multiplied by the time These calculations must considerthe type of air and water distribution systems in the building.Load profiles for two or more energy forms during the sameoperating period may be compared to determine load-matchingcharacteristics under diverse operating conditions For example,when thermal energy is recovered from a diesel-electric generator at

a rate equal to or less than the thermal energy demand, the energycan be used instantaneously, avoiding waste It may be worthwhile

to store thermal energy when it is generated at a greater rate thandemanded A load profile study helps determine the economics ofthermal storage

Similarly, with internal source heat recovery, load matching must

be integrated over the operating season with the aid of load durationcurves for overall feasibility studies These curves are useful inenergy consumption analysis calculations as a basis for hourly inputvalues in computer programs (see Chapter 31 of the ASHRAE Hand-

book—Fundamentals)

Aside from environmental considerations, the economic ity of district heating and cooling is influenced by load density anddiversity factors for branch feeds to buildings along distributionmains For example, the load density or energy per unit length ofdistribution main can be small enough in a complex of low-rise,lightly loaded buildings located at a considerable distance from oneanother, to make a central heating, cooling, or heating and coolingplant uneconomical

feasibil-Concentrations of internal loads peculiar to each application arecovered later in this chapter and in Chapters 28, 29, and 30 of the

ASHRAE Handbook—Fundamentals

The preparation of this chapter is assigned to TC 9.8, Large Building

Air-Conditioning Applications.

Copyright © 2003, ASHRAE

Table 1 General Design Criteria a, b

General Category Specific Category

Inside Design Conditions

Air Movement

Circulation, air changes per hour

15 to 20

Nightclubs and Casinos

10 to 15

Communication

Centers

Telephone Terminal Rooms

8 to 12

Ship Docks

8 to 12

Bus Terminals

Table 1 General Design Criteria a, b(Concluded)

Noise c Filtering Efficiencies (ASHRAE Standard 52.1) Load Profile Comments

NC 35 to 50 Use charcoal for odor control with manual purge control

for 100% outside air to exhaust ±35% prefilters

to NC 60 85% or better Varies with location and use Constant temperature and humidity required

lighting and people Constant temperature and humidity required

Peak at 10 A M to 3 P M

Design Concepts

If a structure is characterized by several exposures and

multipur-pose use, especially with wide load swings and noncoincident

energy use in certain areas, multiunit or unitary systems may be

considered for such areas, but not necessarily for the entire building

The benefits of transferring heat absorbed by cooling from one area

to other areas, processes, or services that require heat may enhance

the selection of such systems Systems such as incremental

closed-loop heat pumps may be cost-effective

When the cost of energy is included in the rent with no means for

permanent or checkmetering, tenants tend to consume excess

energy This energy waste raises operating costs for the owner,

decreases profitability, and has a detrimental effect on the

environ-ment Although design features can minimize excess energy

penal-ties, they seldom eliminate waste For example, U.S Department of

Housing and Urban Development nationwide field records for

total-electric housing show that rent-included dwellings use

approxi-mately 20% more energy than those directly metered by a public

utility company

Diversity factor benefits for central heating and cooling in

rent-included buildings may result in lower building demand and

con-nected loads However, energy waste may easily result in load

fac-tors and annual energy consumption exceeding that of buildings

where the individual has a direct economic incentive to reduce

energy consumption Heat flow meters should be considered for

charging for energy consumption

Design Criteria

In many applications, design criteria are fairly evident, but in all

cases, the engineer should understand the owner’s and user’s intent

because any single factor may influence system selection The

engi-neer’s experience and judgment in projecting future needs may be a

better criterion for system design than any other single factor

Comfort Level Comfort, as measured by temperature,

humid-ity, air motion, air qualhumid-ity, noise, and vibration, is not identical for

all buildings, occupant activities, or uses of space The control of

static electricity may be a consideration in humidity control

Costs Owning and operating costs can affect system selection

and seriously conflict with other criteria Therefore, the engineer

must help the owner resolve these conflicts by considering factors

such as cost and availability of different fuels, ease of equipment

access, and maintenance requirements

Local Conditions Local, state, and national codes, regulations,

and environmental concerns must be considered in design Chapters

26 and 27 of the ASHRAE Handbook—Fundamentals give

informa-tion on calculating the effects of weather in specific areas

Automatic Temperature Control Proper automatic

tempera-ture control maintains occupant comfort during varying internal

and external loads Improper temperature control may mean a loss

of customers in restaurants and other public buildings An energy

management control system can be combined with a building

auto-mation system to allow the owner to manage energy, lighting,

security, fire protection, and other similar systems from one centralcontrol point Chapters 35 and 46 include more details

Fire, Smoke, and Odor Control Fire and smoke can easily

spread through elevator shafts, stairwells, ducts, and other routes

Although an air-conditioning system can spread fire and smoke by(1) fan operation, (2) penetrations required in walls or floors, or (3)the stack effect without fan circulation, a properly designed andinstalled system can be a positive means of fire and smoke control

Chapter 52 has information on techniques for positive controlafter a fire starts Effective attention to fire and smoke control alsohelps prevent odor migration into unventilated areas (see Chapter

45) The design of the ventilation system should consider applicableNational Fire Protection Association standards, especially NFPA

Standards 90A and 96.

DINING AND ENTERTAINMENT

CENTERS Load Characteristics

Air conditioning restaurants, cafeterias, bars, and nightclubs sents common load problems encountered in comfort conditioning,with additional factors pertinent to dining and entertainment appli-cations Such factors include

pre-• Extremely variable loads with high peaks, in many cases, ring twice daily

occur-• High sensible and latent heat gains because of gas, steam, electricappliances, people, and food

• Sensible and latent loads that are not always coincident

• Large quantities of makeup air normally required

• Localized high sensible and latent heat gains in dancing areas

• Unbalanced conditions in restaurant areas adjacent to kitchenswhich, although not part of the conditioned space, still requirespecial attention

• Heavy infiltration of outside air through doors during rush hours

• Smoking versus nonsmoking areasInternal heat and moisture loads come from occupants, motors,lights, appliances, and infiltration Separate calculations should bemade for patrons and employees The sensible and latent heat loadmust be proportioned in accordance with the design temperatureselected for both sitting and working people, because the latent-to-sensible heat ratio for each category decreases as the room temper-ature decreases

Hoods required to remove heat from appliances may also stantially reduce the space latent loads

sub-Infiltration is a considerable factor in many restaurant tions because of short occupancy and frequent door use It isincreased by the need for large quantities of makeup air, whichshould be provided mechanically to replace air exhausted throughhoods and for smoke removal Systems for hood exhaust makeupshould concentrate on exhausting nonconditioned and minimallyheated makeup air Wherever possible, vestibules or revolving doorsshould be installed to reduce infiltration

applica-Notes to Table 1 , General Design Criteria

a This table shows design criteria differences between various commercial and public

build-ings It should not be used as the sole source for design criteria Each type of data contained

here can be determined from the ASHRAE Handbooks and Standards.

b Consult governing codes to determine minimum allowable requirements Outside air

requirements may be reduced if high-efficiency adsorption equipment or other odor- or

gas-removal equipment is used See ASHRAE Standard 62 for calculation procedures Also see

Chapter 45 in this volume and Chapter 13 of the ASHRAE Handbook—Fundamentals.

c Refer to Chapter 47

d Food in these areas is often eaten more quickly than in a restaurant; therefore, turnover of

din-ers is much faster Because dindin-ers seldom remain for long periods, they do not require the

degree of comfort necessary in restaurants Thus, it may be possible to lower design criteria

standards and still provide reasonably comfortable conditions Although space conditions of

27°C and 50% rh may be satisfactory for patrons when it is 35°C and 50% rh outside, inside

conditions of 26°C and 40% rh are better.

e Cafeterias and luncheonettes usually have some or all food preparation equipment and trays in the same room with the diners These establish- ments are generally noisier than restaurants, so noise transmission from air-conditioning equipment is not as critical.

f In some nightclubs, noise from the air-conditioning system must be kept low so patrons can hear the entertainment.

g Usually determined by kitchen hood requirements.

h Peak kitchen heat load does not generally occur at peak dining load, although in luncheonettes and some cafeterias where cooking is done in dining areas, peaks may be simultaneous.

i Methods for removal of chemical pollutants must also be considered.

j Also includes service stations.

Design Concepts

The following factors influence system design and equipment

selection:

• High concentrations of food, body, and tobacco-smoke odors

require adequate ventilation with proper exhaust facilities

• Step control of refrigeration plants gives satisfactory and

econom-ical operation under reduced loads

• Exhausting air at the ceiling removes smoke and odor

• Building design and space limitations often favor one equipment

type over another For example, in a restaurant having a vestibule

with available space above it, air conditioning with condensers

and evaporators remotely located above the vestibule may be

sat-isfactory Such an arrangement saves valuable space, even though

self-contained units located within the conditioned space may be

somewhat lower in initial and maintenance costs In general,

small cafeterias, bars, and the like, with loads up to 35 kW, can be

most economically conditioned with packaged units; larger and

more elaborate establishments require central plants

• Smaller restaurants with isolated plants usually use

direct-expan-sion systems

• Mechanical humidification is typically not provided because of

high internal latent loads

• Some air-to-air heat recovery equipment can reduce the energy

required for heating and cooling ventilation air Chapter 44 of the

ASHRAE Handbook—HVAC Systems and Equipment includes

de-tails The potential for grease condensation on heat recovery

sur-faces must also be considered

• A vapor compression or desiccant-based dehumidifier should

be considered for makeup air handling and enhanced humidity

control

Because eating and entertainment centers generally have low

sensible heat factors and require high ventilation rates, fan-coil and

induction systems are usually not applicable All-air systems are

more suitable Space must be established for ducts, except for small

systems with no ductwork Large establishments are often served by

central chilled-water systems

In cafeterias and luncheonettes, the air distribution system must

keep food odors at the serving counters away from areas where

patrons are eating This usually means heavy exhaust air

require-ments at the serving counters, with air supplied into, and induced

from, eating areas Exhaust air must also remove the heat from hot

trays, coffee urns, and ovens to minimize patron and employee

dis-comfort and to reduce air-conditioning loads These factors often

create greater air-conditioning loads for cafeterias and

luncheon-ettes than for restaurants

Odor Removal Transferring air from dining areas into the

kitchen keeps odors and heat out of dining areas and cools the

kitchen Outside air intake and kitchen exhaust louvers should be

located so that exhaust air is neither drawn back into the system nor

allowed to cause discomfort to passersby

Where odors can be drawn back into dining areas, activated

char-coal filters, air washers, or ozonators are used to remove odors

Kitchen, locker room, toilet, or other malodorous air should not be

recirculated unless air purifiers are used

Kitchen Air Conditioning If planned in the initial design

phases, kitchens can often be air conditioned effectively without

excessive cost It is not necessary to meet the same design criteria

as for dining areas, but kitchen temperatures can be reduced

sig-nificantly The relatively large number of people and food loads in

dining and kitchen areas produce a high latent load Additional

cooling required to eliminate excess moisture increases

refrigera-tion plant, cooling coil, and air-handling equipment size

Advantageously located self-contained units, with air

distri-bution designed so as not to produce drafts off hoods and other

equipment, can be used to spot-cool intermittently High-velocity

air distribution may be effective The costs are not excessive, andkitchen personnel efficiency can be improved greatly

Even in climates with high wet-bulb temperatures, direct or rect evaporative cooling may be a good compromise between theexpense of air conditioning and lack of comfort in ventilated kitch-ens For more information, see Chapter 31, Kitchen Ventilation

indi-Special Considerations

In establishing design conditions, the duration of individualpatron occupancy should be considered Patrons entering from out-side are more comfortable in a room with a high temperature thanthose who remain long enough to become acclimated Nightclubsand deluxe restaurants are usually operated at a lower effective tem-perature than cafeterias and luncheonettes

Often, the ideal design condition must be rejected for an able condition because of equipment cost or performance limita-tions Restaurants are frequently affected in this way because ratios

accept-of latent to sensible heat may result in uneconomical or oversizedequipment selection, unless an enhanced dehumidification system

or a combination of lower design dry-bulb temperature and higherrelative humidity (which gives an equal effective temperature) isselected

In severe climates, entrances and exits in any dining ment should be completely shielded from diners to prevent drafts.Vestibules provide a measure of protection However, both vestibuledoors are often open simultaneously Revolving doors or localmeans for heating or cooling infiltration air may be provided to off-set drafts

establish-Uniform employee comfort is difficult to maintain because of(1) temperature differences between the kitchen and dining roomand (2) the constant motion of employees Because customer satis-faction is essential to a dining establishment’s success, patron com-fort is the primary consideration However, maintaining satisfactorytemperature and atmospheric conditions for customers also helpsalleviate employee discomfort

One problem in dining establishments is the use of partitions toseparate areas into modular units Partitions create such variedload conditions that individual modular unit control is generallynecessary

Baseboard radiation or convectors, if required, should be located

so as not to overheat patrons This is difficult to achieve in some outs because of movable chairs and tables For these reasons, it isdesirable to enclose all dining room and bar heating elements ininsulated cabinets with top outlet grilles and baseboard inlets Withheating elements located under windows, this practice has the addi-tional advantage of directing the heat stream to combat windowdowndraft and air infiltration Separate smoking and nonsmokingareas may be required The smoking area should be exhausted orserved by separate air-handling equipment Air diffusion deviceselection and placement should minimize smoke migration towardnonsmoking areas Smoking areas must have a negative air pressurerelationship with adjacent occupied areas

lay-Restaurants In restaurants, people are seated and served at

tables, and food is generally prepared in remote areas This type ofdining is usually enjoyed in a leisurely and quiet manner, so theambient atmosphere should be such that the air conditioning is notnoticed Where specialized or open cooking is a feature, provisionsshould be made for control and handling of cooking odors andsmoke

Bars Bars are often a part of a restaurant or nightclub If they

are establishments on their own, they often serve food as well asdrinks, and they should be classified as restaurants with food prep-aration in remote areas Alcoholic beverages produce pungentvapors, which must be drawn off In addition, smoking at bars isgenerally considerably heavier than in restaurants Therefore, out-side air requirements are relatively high by comparison

Nightclubs and Casinos Both nightclubs and casinos may

include a restaurant, bar, stage, and dancing area The bar should be

treated as a separately zoned area, with its own supply and exhaust

system People in the restaurant area who dine and dance may

require twice the air changes and cooling required by patrons who

dine and then watch a show The length of stay generally exceeds

that encountered in most eating places In addition, eating in

night-clubs and casinos is usually secondary to drinking and smoking

Patron density usually exceeds that of conventional eating

establish-ments

Kitchens The kitchen has the greatest concentration of noise,

heat load, smoke, and odors; ventilation is the chief means of

removing these objectionable elements and preventing them from

entering dining areas To ensure odor control, kitchen air pressure

should be kept negative relative to other areas Maintenance of

rea-sonably comfortable working conditions is important For more

information, see Chapter 31, Kitchen Ventilation

OFFICE BUILDINGS Load Characteristics

Office buildings usually include both peripheral and interior

zone spaces The peripheral zone extends from 3 to 3.6 m inward

from the outer wall toward the interior of the building and frequently

has a large window area These zones may be extensively

subdi-vided Peripheral zones have variable loads because of changing sun

position and weather These zone areas typically require heating in

winter During intermediate seasons, one side of the building may

require cooling, while another side requires heating However, the

interior zone spaces usually require a fairly uniform cooling rate

throughout the year because their thermal loads are derived almost

entirely from lights, office equipment, and people Interior space

conditioning is often by systems that have variable air volume

con-trol for low- or no-load conditions

Most office buildings are occupied from approximately 8:00 A.M

to 6:00 P.M.; many are occupied by some personnel from as early as

5:30 A.M to as late as 7:00 P.M Some tenants’ operations may

require night work schedules, usually not to extend beyond 10:00

P.M Office buildings may contain printing plants, communications

operations, broadcasting studios, and computing centers, which

could operate 24 h per day Therefore, for economical

air-condition-ing design, the intended uses of an office buildair-condition-ing must be well

established before design development

Occupancy varies considerably In accounting or other sections

where clerical work is done, the maximum density is approximately

one person per 7 m2 of floor area Where there are private offices,

the density may be as little as one person per 19 m2 The most

seri-ous cases, however, are the occasional waiting rooms, conference

rooms, or directors’ rooms where occupancy may be as high as one

person per 2 m2

The lighting load in an office building constitutes a significant

part of the total heat load Lighting and normal equipment electrical

loads average from 10 to 50 W/m2 but may be considerably higher,

depending on the type of lighting and the amount of equipment

Buildings with computer systems and other electronic equipment

can have electrical loads as high as 50 to 110 W/m2 An accurate

appraisal should be made of the amount, size, and type of computer

equipment anticipated for the life of the building to size the

air-handling equipment properly and provide for future installation of

air-conditioning apparatus

About 30% of the total lighting heat output from recessed

fix-tures can be withdrawn by exhaust or return air and, therefore, will

not enter into space-conditioning supply air requirements By

con-necting a duct to each fixture, the most balanced air system can be

provided However, this method is expensive, so the suspended

ceiling is often used as a return air plenum with the air drawn from

the space to above the suspended ceiling

Miscellaneous allowances (for fan heat, duct heat pickup, ductleakage, and safety factors) should not exceed 12% of the total load

Building shape and orientation are often determined by the ing site, but certain variations in these factors can increase refriger-ation load by 10 to 15% Shape and orientation should therefore becarefully analyzed in the early design stages

build-Design Concepts

The variety of functions and range of design criteria applicable tooffice buildings have allowed the use of almost every available air-conditioning system Multistory structures are discussed here, butthe principles and criteria are similar for all sizes and shapes ofoffice buildings

Attention to detail is extremely important, especially in modularbuildings Each piece of equipment, duct and pipe connections,and the like may be duplicated hundreds of times Thus, seeminglyminor design variations may substantially affect construction andoperating costs In initial design, each component must be ana-lyzed not only as an entity, but also as part of an integrated system

This systems design approach is essential for achieving optimumresults

There are several classes of office buildings, determined by thetype of financing required and the tenants who will occupy thebuilding Design evaluation may vary considerably based on spe-cific tenant requirements; it is not enough to consider typical floorpatterns only Included in many larger office buildings are stores,restaurants, recreational facilities, data centers, telecommunicationcenters, radio and television studios, and observation decks

Built-in system flexibility is essential for office building design

Business office procedures are constantly being revised, and basicbuilding services should be able to meet changing tenant needs

The type of occupancy may have an important bearing on theselection of the air distribution system For buildings with oneowner or lessee, operations may be defined clearly enough that asystem can be designed without the degree of flexibility needed for

a less well-defined operation However, owner-occupied buildingsmay require considerable design flexibility because the owner willpay for all alterations The speculative builder can generally chargealterations to tenants When different tenants occupy differentfloors, or even parts of the same floor, the degree of design and oper-ation complexity increases to ensure proper environmental comfortconditions to any tenant, group of tenants, or all tenants at once

This problem is more acute if tenants have seasonal and variableovertime schedules

Stores, banks, restaurants, and entertainment facilities may havehours of occupancy or design criteria that differ substantially fromthose of office buildings; therefore, they should have their own airdistribution systems and, in some cases, their own heating and/orrefrigeration equipment

Main entrances and lobbies are sometimes served by a separatesystem because they buffer the outside atmosphere and the buildinginterior Some engineers prefer to have a lobby summer temperature

2 to 3.5 K above office temperature to reduce operating cost and temperature shock to people entering or leaving the building

the-The unique temperature and humidity requirements of data cessing installations and the fact that they often run 24 h per day forextended periods generally warrant separate refrigeration and airdistribution systems Separate backup systems may be required fordata processing areas in case the main building HVAC system fails

pro-Chapter 17 has further information

The degree of air filtration required should be determined Theservice cost and the effect of air resistance on energy costs should beanalyzed for various types of filters Initial filter cost and air pollu-tion characteristics also need to be considered Activated charcoalfilters for odor control and reduction of outside air requirements areanother option to consider

Providing office buildings with continuous 100% outside air is

seldom justified; therefore, most office buildings are designed to

minimize outside air use, except during economizer operation

However, attention to inside air quality may dictate higher levels of

ventilation air In addition, the minimum volume of outside air

should be maintained in variable-volume air-handling systems

Dry-bulb or enthalpy-controlled economizer cycles should be

con-sidered for reducing energy costs

When an economizer cycle is used, systems should be zoned so

that energy waste will not occur by heating outside air This is often

accomplished by a separate air distribution system for the interior

and each major exterior zone

High-rise office buildings have traditionally used perimeter

dual-duct, induction, or fan-coil systems Where fan-coil or induction

sys-tems have been installed at the perimeter, separate all-air syssys-tems

have generally been used for the interior More recently, variable air

volume systems, including modulated air diffusers and

self-con-tained perimeter unit systems, have also been used If variable air

volume systems serve the interior, perimeters are usually served by

variable-volume or dual-duct systems supplemented with

fan-pow-ered terminals, terminals with reheat coils, or radiation (ceiling

pan-els or baseboard) The perimeter systems can be hydronic or electric

Many office buildings without an economizer cycle have a

bypass multizone unit installed on each floor or several floors with

a heating coil in each exterior zone duct Variable air volume

varia-tions of the bypass multizone and other floor-by-floor, all-air

sys-tems are also being used These syssys-tems are popular because of their

low fan power and initial cost, and energy savings from independent

operating schedules, which are possible between floors occupied by

tenants with different operating hours

Perimeter radiation or infrared systems with conventional,

sin-gle-duct, low-velocity air conditioning that furnishes air from

pack-aged air-conditioning units or multizone units may be more

economical for small office buildings The need for a perimeter

sys-tem, which is a function of exterior glass percentage, external wall

thermal value, and climate severity, should be carefully analyzed

A perimeter heating system separate from the cooling system is

preferable, because air distribution devices can then be selected for

a specific duty rather than as a compromise between heating and

cooling performance The higher cost of additional air-handling or

fan-coil units and ductwork may lead the designer to a less

expen-sive option, such as fan-powered terminal units with heating coils

serving perimeter zones in lieu of a separate heating system

Radi-ant ceiling panels for the perimeter zones are another option

Interior space usage usually requires that interior

air-condition-ing systems allow modification to handle all load situations

Vari-able air volume systems are often used When using these systems,

low-load conditions should be carefully evaluated to determine

whether adequate air movement and outside air can be provided at

the proposed supply air temperature without overcooling Increases

in supply air temperature tend to nullify energy savings in fan

power, which are characteristic of variable air volume systems

Low-temperature air distribution for additional savings in transport

energy is seeing increased use, especially when coupled with an ice

storage system

In small to medium-sized office buildings, air-source heat pumps

may be chosen In larger buildings, internal source heat pump

sys-tems (water-to-water) are feasible with most types of

air-condition-ing systems Heat removed from core areas is rejected to either a

cooling tower or perimeter circuits The internal source heat pump

can be supplemented by a central heating system or electrical coils

on extremely cold days or over extended periods of limited

occu-pancy Removed excess heat may also be stored in hot-water tanks

Many heat recovery or internal-source heat pump systems

exhaust air from conditioned spaces through lighting fixtures

Approximately 30% of lighting heat can be removed in this manner

One design advantage is a reduction in required air quantities In

addition, lamp life is extended by operation in a much cooler ent environment

ambi-Suspended ceiling return air plenums eliminate sheet metalreturn air ductwork to reduce floor-to-floor height requirements.However, suspended ceiling plenums may increase the difficulty ofproper air balancing throughout the building Problems often con-nected with suspended ceiling return plenums are as follows:

• Air leakage through cracks, with resulting smudges

• Tendency of return air openings nearest to a shaft opening or lector duct to pull too much air, thus creating uneven air motionand possible noise

col-• Noise transmission between office spacesAir leakage can be minimized by proper workmanship To over-come drawing too much air, return air ducts can be run in the sus-pended ceiling pathway from the shaft, often in a simple radialpattern Ends of the ducts can be left open or dampered Generoussizing of return air grilles and passages lowers the percentage ofcircuit resistance attributable to the return air path This bolsterseffectiveness of supply air balancing devices and reduces the signif-icance of air leakage and drawing too much air Structural blockagecan be solved by locating openings in beams or partitions with firedampers, where required

Spatial Requirements

Total office building electromechanical space requirements varytremendously based on types of systems planned; however, the aver-age is approximately 8 to 10% of the gross area Clear heightrequired for fan rooms varies from approximately 3 to 5.5 m,depending on the distribution system and equipment complexity

On office floors, perimeter fan-coil or induction units requireapproximately 1 to 3% of the floor area Interior air shafts and pipechases require approximately 3 to 5% of the floor area Therefore,ducts, pipes, and equipment require approximately 4 to 8% of eachfloor’s gross area

Where large central units supply multiple floors, shaft spacerequirements depend on the number of fan rooms In such cases, onemechanical equipment room usually furnishes air requirements for

8 to 20 floors (above and below for intermediate levels), with anaverage of 12 floors The more floors served, the larger the ductshafts and equipment required This results in higher fan roomheights and greater equipment size and mass

The fewer floors served by an equipment room, the greater theflexibility in serving changing floor or tenant requirements Often,one mechanical equipment room per floor and complete elimination

of vertical shafts requires no more total floor area than fewer largermechanical equipment rooms, especially when there are many smallrooms and they are the same height as typical floors Equipment canalso be smaller, although maintenance costs will be higher Energycosts may be reduced with more equipment rooms serving fewerareas, because equipment can be shut off in unoccupied areas, andhigh-pressure ductwork will not be required Equipment rooms onupper levels generally cost more to install because of rigging andtransportation logistics

In all cases, mechanical equipment rooms must be thermally andacoustically isolated from office areas

Cooling Towers Cooling towers are the largest single piece of

equipment required for air-conditioning systems Cooling towersrequire approximately 1 m2 of floor area per 400 m2 of total build-ing area and are 4 to 12 m high When towers are located on theroof, the building structure must be capable of supporting the cool-ing tower and dunnage, full water load (approximately 590 to

730 kg/m2), and seismic and wind load stresses

Where cooling tower noise may affect neighboring buildings,towers should be designed to include sound traps or other suitablenoise baffles This may affect tower space, mass of the units, andmotor power Slightly oversizing cooling towers can reduce noise

and power consumption because of lower speeds, but this may

increase initial cost

Cooling towers are sometimes enclosed in a decorative screen

for aesthetic reasons; therefore, calculations should ascertain that

the screen has sufficient free area for the tower to obtain its required

air quantity and to prevent recirculation

If the tower is placed in a rooftop well or near a wall, or split into

several towers at various locations, design becomes more

compli-cated, and initial and operating costs increase substantially Also,

towers should not be split and placed on different levels because

hydraulic problems increase Finally, the cooling tower should be

built high enough above the roof so that the bottom of the tower and

the roof can be maintained properly

Special Considerations

Office building areas with special ventilation and cooling

re-quirements include elevator machine rooms, electrical and

tele-phone closets, electrical switchgear, plumbing rooms, refrigeration

rooms, and mechanical equipment rooms The high heat loads in

some of these rooms may require air-conditioning units for spot

cooling

In larger buildings with intermediate elevator, mechanical, and

electrical machine rooms, it is desirable to have these rooms on the

same level or possibly on two levels This may simplify horizontal

ductwork, piping, and conduit distribution systems and permit more

effective ventilation and maintenance of these equipment rooms

An air-conditioning system cannot prevent occupants at the

perimeter from feeling direct sunlight Venetian blinds and drapes

are often provided but seldom used External shading devices

(screens, overhangs, etc.) or reflective glass are preferable

Tall buildings in cold climates experience severe stack effect

The extra amount of heat provided by the air-conditioning system in

attempts to overcome this problem can be substantial The

follow-ing features help combat infiltration from the stack effect:

• Revolving doors or vestibules at exterior entrances

• Pressurized lobbies or lower floors

• Tight gaskets on stairwell doors leading to the roof

• Automatic dampers on elevator shaft vents

• Tight construction of the exterior skin

• Tight closure and seals on all dampers opening to the

exterior

BOWLING CENTERS

Bowling centers may also contain a bar, a restaurant, a children’s

play area, offices, locker rooms, and other types of facilities Such

auxiliary areas are not discussed in this section, except as they may

affect design for the bowling area, which consists of alleys and a

spectator area

Load Characteristics

Bowling alleys usually have their greatest period of use in the

evenings, but weekend daytime use may also be heavy Thus, when

designing for the peak air-conditioning load on the building, it is

necessary to compare the day load and its high outside solar load

and off-peak people load with the evening peak people load and zero

solar load Because bowling areas generally have little fenestration,

solar load may not be important

If the building contains auxiliary areas, these areas may be

included in the refrigeration, heating, and air distribution systems

for the bowling alleys, with suitable provisions for zoning the

dif-ferent areas as dictated by load analysis Alternatively, separate

sys-tems may be established for each area having different load

operation characteristics

Heat buildup from lights, external transmission load, and

pin-setting machinery in front of the foul line can be reduced by

exhausting some air above the alleys or from the area containing thepin-setting machines; however, this gain should be comparedagainst the cost of conditioning additional makeup air In calculat-ing the air-conditioning load, a portion of the unoccupied alleyspace load is included Because this consists mainly of lights andsome transmission load, about 15 to 30% of this heat load may have

to be taken into account The higher figure may apply when the roof

is poorly insulated, no exhaust air is taken from this area, or no tical baffle is used at the foul line One estimate is 16 to 32 W persquare metre of vertical surface at the foul line, depending mostly onthe type and intensity of the lighting

ver-The heat load from bowlers and spectators may be found in Table

1 in Chapter 29 of the ASHRAE Handbook—Fundamentals The

proper heat gain should be applied for each person to avoid too large

a design heat load

Design Concepts

As with other building types having high occupancy loads, heavysmoke and odor concentration, and low sensible heat factors, all-airsystems are generally the most suitable for bowling alley areas

Because most bowling alleys are almost windowless except for suchareas as entrances, exterior restaurants, and bars, it is uneconomical

to use terminal unit systems because of the small number required

Where required, radiation in the form of baseboard or radiant ing panels is generally placed at perimeter walls and entrances

ceil-It is not necessary to maintain normal inside temperatures downthe length of the alleys; temperatures may be graded down to the pinarea Unit heaters are often used at this location

Air Pressurization Spectator and bowling areas must be well

shielded from entrances so that no cold drafts are created in theseareas To minimize infiltration of outside air into the alleys, the ex-haust and return air system should handle only 85 to 90% of the totalsupply air, maintaining a positive pressure in the space when outsideair pressurization is taken into consideration

Air Distribution Packaged units without ductwork produce

uneven space temperatures, and unless they are carefully locatedand installed, the units may cause objectionable drafts Central duct-work is recommended for all but the smallest buildings, even wherepackaged refrigeration units are used Because only the areasbehind the foul line are air conditioned, the ductwork should pro-vide comfortable conditions within this area

The return and exhaust air systems should have a large number ofsmall registers uniformly located at high points, or pockets, to drawoff the hot, smoky, and odorous air In some parts of the country andfor larger bowling alleys, it may be desirable to use all outside air tocool during intermediate seasons

Special Considerations

People in sports and amusement centers engage in a high degree

of physical activity, which makes them feel warmer and increasestheir rate of evaporation In these places, odor and smoke control areimportant environmental considerations

Bowling centers are characterized by the following:

• A large number of people concentrated in a relatively small area

of a very large room A major portion of the floor area is cupied

unoc-• Heavy smoking, high physical activity, and high latent heat load

• Greatest use from about 6:00 P.M to midnight

The first two items make furnishing large amounts of outside airmandatory to minimize odors and smoke in the atmosphere

The area between the foul line and the bowling pins need not beair conditioned or ventilated Transparent or opaque vertical parti-tions are sometimes installed to separate the upper portions of theoccupied and unoccupied areas so that air distribution is better con-tained within the occupied area

COMMUNICATION CENTERS

Communication centers include telephone terminal buildings,

radio stations, television studios, and transmitter and receiver

sta-tions Most telephone terminal rooms are air conditioned because

constant temperature and relative humidity help prevent

break-downs and increase equipment life In addition, air conditioning

permits the use of a lower number of air changes, which, for a given

filter efficiency, decreases the chances of damage to relay contacts

and other delicate equipment

Radio and television studios require critical analysis for the

elim-ination of heat build-up and the control of noise Television studios

have the added problem of air movement, lighting, and occupancy

load variations This section deals with television studios because

they present most of the problems also found in radio studios

Load Characteristics

Human occupancy is limited in telephone terminal rooms, so the

air-conditioning load is primarily equipment heat load

Television studios have very high lighting capacities, and the

lighting load may fluctuate considerably in intensity over short

peri-ods Operating hours may vary every day In addition, there may be

from one to several dozen people onstage for short times The

air-conditioning system must be extremely flexible and capable of

han-dling wide load variations quickly, accurately, and efficiently,

sim-ilar to the conditions of a theater stage The studio may also have an

assembly area with a large number of spectator seats Generally,

stu-dios are located so that they are completely shielded from external

noise and thermal environments

Design Concepts

The critical areas of a television studio are the performance

stu-dio and control rooms The audience area may be treated much like

a place of assembly Each area should have its own air distribution

system or at least its own zone control separate from the studio

sys-tem Heat generated in the studio area should not be allowed to

per-meate the audience atmosphere

The air distribution system selected must have the capabilities of

a dual-duct, single-duct system with cooling and heating booster

coils, a variable air volume system, or a multizone system to satisfy

design criteria The air distribution system should be designed so

that simultaneous heating and cooling cannot occur unless heating

is achieved solely by heat recovery

Studio loads seldom exceed 350 kW of refrigeration Even if the

studio is part of a large communications center or building, the

stu-dio should have its own refrigeration system in case of emergencies

The refrigeration equipment in this size range may be reciprocating

units, which require a remote location so that machine noise is

iso-lated from the studio

Special Considerations

On-Camera Studio This is the “stage” of the television studio

and requires the same general considerations as a concert hall

stage Air movement must be uniform, and, because scenery,

cam-eras, and equipment may be moved during the performance,

duct-work must be planned carefully to avoid interference with proper

studio operation

Control Room Each studio may have one or more control

rooms serving different functions The video control room, which

is occupied by the program and technical directors, contains

mon-itors and picture-effect controls The room may require up to 30 air

changes per hour to maintain proper conditions The large number

of necessary air changes and the low sound level that must be

main-tained require special analysis of the air distribution system

If a separate control room is furnished for the announcer, the heat

load and air distribution problems will not be as critical as those for

control rooms for the program, technical, and audio directors

Thermostatic control should be furnished in each control room,and provisions should be made to enable occupants to turn the airconditioning on and off

Noise Control Studio microphones are moved throughout the

studio during a performance, and they may be moved past or set nearair outlets or returns These microphones are considerably moresensitive than the human ear; therefore, air outlets or returns should

be located away from areas where microphones are likely to beused Even a leaky pneumatic thermostat can be a problem

Air Movement It is essential that air movement in the stage

area, which often contains scenery and people, be kept below0.13 m/s within 3.7 m of the floor The scenery is often fragile andwill move in air velocities above 0.13 m/s; also, actors’ hair andclothing may be disturbed

Air Distribution Ductwork must be fabricated and installed so

that there are no rough edges, poor turns, or improperly installeddampers to cause turbulence and eddy currents in the ducts Duct-work should contain no holes or openings that might create whis-tles Air outlet locations and the distribution pattern must becarefully analyzed to eliminate turbulence and eddy currents in thestudio that might cause noise that could be picked up by studiomicrophones

At least some portions of supply, return, and exhaust ductworkwill require acoustical material to maintain noise criterion (NC)levels from 20 to 25 Any duct serving more than one room shouldacoustically separate each room by means of a sound trap All duct-work should be suspended by means of neoprene or rubber inshear-type vibration mountings Where ductwork goes throughwall or floor slabs, the openings should be sealed with acousticallydeadening material The supply fan discharge and the return andexhaust fan inlets should have sound traps; all ductwork connec-tions to fans should be made with nonmetallic, flexible material.Air outlet locations should be coordinated with ceiling-mountedtracks and equipment Air distribution for control rooms mayrequire a perforated ceiling outlet or return air plenum system

Piping Distribution All piping in the studio, as well as in

ad-jacent areas that might transmit noise to the studio, should besupported by suitable vibration isolation hangers To prevent trans-mitting vibration, piping should be supported from rigid structuralelements to maximize absorption

Mechanical Equipment Room This room should be located as

far from the studio as possible All equipment should be selected forvery quiet operation and should be mounted on suitable vibration-eliminating supports Structural separation of the room from the stu-dio is generally required

Offices and Dressing Rooms The functions of these rooms are

quite different from each other and from the studio areas It is ommended that such rooms be treated as separate zones, with theirown controls

rec-Air Return Whenever practicable, the largest portion of studio

air should be returned over the banks of lights This is similar to ater stage practice Sufficient air should also be removed from stu-dio high points to prevent heat build-up

the-TRANSPORTATION CENTERS

The major transportation facilities are airports, ship docks, busterminals, and passenger car garages Airplane hangars andfreight and mail buildings are also among the types of buildings

to be considered Freight and mail buildings are usually handled

as standard warehouses

Load Characteristics

Airports, ship docks, and bus terminals operate on a 24 h basis,with a reduced schedule during late night and early morning hours

Airports Terminal buildings consist of large, open circulating

areas, one or more floors high, often with high ceilings, ticketingcounters, and various types of stores, concessions, and convenience

facilities Lighting and equipment loads are generally average, but

occupancy varies substantially Exterior loads are, of course, a

func-tion of architectural design The largest single problem often is

ther-mal drafts created by large entranceways, high ceilings, and long

passageways, which have many openings to the outside

Ship Docks Freight and passenger docks consist of large,

high-ceilinged structures with separate areas for administration, visitors,

passengers, cargo storage, and work The floor of the dock is usually

exposed to the outside just above the water level Portions of the side

walls are often open while ships are in port In addition, the large

ceiling (roof) area presents a large heating and cooling load Load

characteristics of passenger dock terminals generally require the

roof and floors to be well insulated Occasional heavy occupancy

loads in visitor and passenger areas must be considered

Bus Terminals This building type consists of two general areas:

the terminal building, which contains passenger circulation, ticket

booths, and stores or concessions, and the bus loading area Waiting

rooms and passenger concourse areas are subject to a highly

vari-able people load Occupancy density may reach 1 m2 per person

and, at extreme periods, 0.3 to 0.5 m2 per person Chapter 13,

Enclosed Vehicular Facilities, has further information on bus

termi-nals

Design Concepts

Heating and cooling is generally centralized or provided for each

building or group in a complex In large, open-circulation areas of

transportation centers, any all-air system with zone control can be

used Where ceilings are high, air distribution is often along the side

wall to concentrate the air conditioning where desired and avoid

dis-turbing stratified air Perimeter areas may require heating by

radia-tion, a fan-coil system, or hot air blown up from the sill or floor

grilles, particularly in colder climates Hydronic perimeter radiant

ceiling panels may be especially suited to these high-load areas

Airports Airports generally consist of one or more central

terminal buildings connected by long passageways or trains to

rotundas containing departure lounges for airplane loading Most

terminals have portable telescoping-type loading bridges

connect-ing departure lounges to the airplanes These passageways eliminate

the heating and cooling problems associated with traditional

perma-nent structure passenger loading

Because of difficulties in controlling the air balance because of

the many outside openings, high ceilings, and long, low

passage-ways (which often are not air conditioned), the terminal building

(usually air conditioned) should be designed to maintain a

substan-tial positive pressure Zoning is generally required in passenger

waiting areas, in departure lounges, and at ticket counters to take

care of the widely variable occupancy loads

Main entrances may have vestibules and windbreaker partitions

to minimize undesirable air currents in the building

Hangars must be heated in cold weather, and ventilation may be

required to eliminate possible fumes (although fueling is seldom

permitted in hangars) Gas-fired, electric, and low- and

high-inten-sity radiant heaters are used extensively in hangars because they

provide comfort for employees at relatively low operating costs

Hangars may also be heated by large air blast heaters or

floor-buried heated liquid coils Local exhaust air systems may be used to

evacuate fumes and odors that occur in smaller ducted systems

Under some conditions, exhaust systems may be portable and may

include odor-absorbing devices

Ship Docks In severe climates, occupied floor areas may

con-tain heated floor panels The roof should be well insulated, and, in

appropriate climates, evaporative spray cooling substantially

re-duces the summer load Freight docks are usually heated and well

ventilated but seldom cooled

High ceilings and openings to the outside may present serious

draft problems unless the systems are designed properly Vestibule

entrances or air curtains help minimize cross-drafts Air door blastheaters at cargo opening areas may be quite effective

Ventilation of the dock terminal should prevent noxious fumesand odors from reaching occupied areas Therefore, occupied areasshould be under positive pressure, and cargo and storage areasexhausted to maintain negative air pressure Occupied areas should

be enclosed to simplify any local air conditioning

In many respects, these are among the most difficult buildings toheat and cool because of their large open areas If each function isproperly enclosed, any commonly used all-air or large fan-coil sys-tem is suitable If areas are left largely open, the best approach is toconcentrate on proper building design and heating and cooling ofthe openings High-intensity infrared spot heating is often advanta-geous (see Chapter 15 of the ASHRAE Handbook—Systems and

Equipment) Exhaust ventilation from tow truck and cargo areasshould be exhausted through the roof of the dock terminal

Bus Terminals Conditions are similar to those for airport

termi-nals, except that all-air systems are more practical because ceilingheights are often lower, and perimeters are usually flanked by stores

or office areas The same systems are applicable as for airport minals, but ceiling air distribution is generally feasible

ter-Properly designed radiant hydronic or electric ceiling systemsmay be used if high-occupancy latent loads are fully considered

This may result in smaller duct sizes than are required for all-air tems and may be advantageous where bus loading areas are abovethe terminal and require structural beams This heating and coolingsystem reduces the volume of the building that must be conditioned

sys-In areas where latent load is a concern, heating-only panels may beused at the perimeter, with a cooling-only interior system

The terminal area air supply system should be under high tive pressure to ensure that no fumes and odors infiltrate from busareas Positive exhaust from bus loading areas is essential for aproperly operating total system (see Chapter 13)

posi-Special Considerations

Airports Filtering outside air with activated charcoal filters

should be considered for areas subject to excessive noxious fumesfrom jet engine exhausts However, locating outside air intakes asremotely as possible from airplanes is a less expensive and morepositive approach

Where ionization filtration enhancers are used, outside air tities are sometimes reduced because of cleaner air However, caremust be taken to maintain sufficient amounts of outside air for spacepressurization

quan-Ship Docks Ventilation design must ensure that fumes and

odors from forklifts and cargo in work areas do not penetrate pied and administrative areas

occu-Bus Terminals The primary concerns with enclosed bus loading

areas are health and safety problems, which must be handled byproper ventilation (see Chapter 13) Although diesel engine fumesare generally not as noxious as gasoline fumes, bus terminals oftenhave many buses loading and unloading at the same time, and thetotal amount of fumes and odors may be quite disturbing

Enclosed Garages In terms of health and safety, enclosed bus

loading areas and automobile parking garages present the mostserious problems in these buildings Three major problems areencountered The first and most serious is emission of carbon mon-oxide (CO) by cars and oxides of nitrogen by buses, which cancause serious illness and possibly death The second problem is oiland gasoline fumes, which may cause nausea and headaches andcan also create a fire hazard The third is lack of air movement andthe resulting stale atmosphere that develops because of increasedcarbon dioxide content in the air This condition may cause head-aches or grogginess Most codes require a minimum ventilation rate

to ensure that the CO concentration does not exceed safe limits

Chapter 13 covers ventilation requirements and calculation dures for enclosed vehicular facilities in detail

All underground garages should have facilities for testing the CO

concentration or should have the garage checked periodically

Clogged duct systems; improperly operating fans, motors, or

damp-ers; clogged air intake or exhaust louvers, etc., may not allow proper

air circulation Proper maintenance is required to minimize any

operational defects

WAREHOUSES

Warehouses are used to store merchandise and may be open to

the public at times They are also used to store equipment and

mate-rial inventory at industmate-rial facilities The buildings are generally not

air conditioned, but often have sufficient heat and ventilation to

pro-vide a tolerable working environment Associated facilities

occu-pied by office workers, such as shipping, receiving, and inventory

control offices, are generally air conditioned

Load Characteristics

Internal loads from lighting, people, and miscellaneous sources

are generally low Most of the load is thermal transmission and

infil-tration An air-conditioning load profile tends to flatten where

mate-rials stored are massive enough to cause the peak load to lag

Design Concepts

Most warehouses are only heated and ventilated Forced flow

unit heaters may be located near heat entrances and work areas

Large central heating and ventilating units are widely used Even

though comfort for warehouse workers may not be considered, it

may be necessary to keep the temperature above 4°C to protect

sprinkler piping or stored materials from freezing

A building designed for the addition of air conditioning at a

later date will require less heating and be more comfortable For

maximum summer comfort without air conditioning, excellent

ventilation with noticeable air movement in work areas is sary Even greater comfort can be achieved in appropriate climates

neces-by adding roof spray cooling This can reduce the roof’s surfacetemperature by 20 to 30 K, thereby reducing ceiling radiationinside Low- and high-intensity radiant heaters can be used tomaintain the minimum ambient temperature throughout a facilityabove freezing Radiant heat may also be used for occupant com-fort in areas permanently or frequently open to the outside

If the stored product requires defined inside conditions, an conditioning system must be added Using only ventilation mayhelp in maintaining lower space temperature, but caution should beexercised not to damage the stored product with uncontrolledhumidity Direct or indirect evaporative cooling may also be anoption

air-Special Considerations

Forklifts and trucks powered by gasoline, propane, and otherfuels are often used inside warehouses Proper ventilation is neces-sary to alleviate the buildup of CO and other noxious fumes Properventilation of battery-charging rooms for electrically powered fork-lifts and trucks is also required

NFPA 1994 Ventilation control and fire protection of commercial cooking

operations Standard 96-2001 National Fire Protection Association,

Quincy, MA.

NFPA 1996 Installation of air conditioning and ventilating systems ANSI/

NFPA Standard 90A-2002 National Fire Protection Association,

Quincy, MA.

Arenas and Stadiums 4.4

Convention and Exhibition Centers 4.5

Natatoriums 4.5

Fairs and Other Temporary Exhibits 4.8

Atriums 4.8

SSEMBLY rooms are generally large, have relatively high

ceil-A ings, and are few in number for any given facility They

usu-ally have a periodicusu-ally high density of occupancy per unit floor

area, as compared to other buildings, and thus have a relatively low

design sensible heat ratio

This chapter summarizes some of the design concerns for

enclosed assembly buildings (Chapter 3, which covers general

cri-teria for commercial and public buildings, also includes information

that applies to public assembly buildings.)

GENERAL CRITERIA

Energy conservation codes and standards must be considered

because they have a major impact on design and performance

Assembly buildings may have relatively few hours of use per

week and may not be in full use when maximum outdoor

tempera-tures or solar loading occur Often they are fully occupied for as

lit-tle as 1 to 2 h, and the load may be materially reduced by precooling

The designer needs to obtain as much information as possible about

the anticipated hours of use, particularly the times of full seating, so

that simultaneous loads may be considered to obtain optimum

per-formance and operating economy Dehumidification requirements

should be considered before reducing equipment size The

intermit-tent or infrequent nature of the cooling loads may allow these

build-ings to benefit from thermal storage systems

The occupants usually generate the major room cooling and

ven-tilation load The number of occupants is best determined from the

seat count, but when this is not available, it can be estimated at 0.7

to 0.9 m2 per person for the entire seating area, including exit aisles

but not the stage, performance areas, or entrance lobbies

Outdoor Air

Outdoor air ventilation rates as prescribed by ASHRAE

Stan-dard 62 can be a major portion of the total load The latent load

(dehumidification and humidification) and energy used to maintain

the relative humidity within prescribed limits is also a concern

Humidity must be maintained at proper levels to prevent mold and

mildew growth and for acceptable indoor air quality and comfort

Lighting Loads

Lighting loads are one of the few major loads that vary from

one type of assembly building to another Lighting may be at the

level of 1600 lux in convention halls where television cameras are

expected to be used, or lighting may be virtually absent, as in a

movie theater In many assembly buildings, lights are controlled

by dimmers or other means to present a suitably low level of light

during performances, with much higher lighting levels during

cleanup, when the house is nearly empty The designer should

ascertain the light levels associated with maximum occupancies,

not only for economy but also to determine the proper room

sen-sible heat ratio

Indoor Air Conditions

Indoor air temperature and humidity should follow ASHRAEcomfort recommendations in Chapter 8 of the ASHRAE Hand-

book—Fundamentals and ASHRAE Standard 55 In addition, the

following should be considered:

• In arenas, stadiums, gymnasiums, and movie theaters, peoplegenerally dress informally Summer indoor conditions may favorthe warmer end of the thermal comfort scale while the winterindoor temperature may favor the cooler end of the scale

• In churches, concert halls, and theaters, most men wear jacketsand ties and women often wear suits The temperature shouldfavor the middle range of design, and there should be littlesummer-to-winter variation

• In convention and exhibition centers, the public is continuallywalking Here the indoor temperature should favor the lowerrange of comfort conditions both in summer and in winter

• In spaces with a high population density or with a sensible heatfactor of 0.75 or less, reheat should be considered

• Energy conservation codes must be considered in both the designand during operation

Assembly areas generally require some reheat to maintain therelative humidity at a suitably low level during periods of maximumoccupancy Refrigerant hot gas or condenser water is well suited forthis purpose Face and bypass control of low-temperature coolingcoils is also effective In colder climates, it may also be desirable toprovide humidification High rates of internal gain may make evap-orative humidification attractive during economizer cooling

Filtration

Most places of assembly are minimally filtered with filters rated

at 30 to 35% efficiency, as tested in accordance with ASHRAE

Standard 52.1 Where smoking is permitted, however, filters with a

minimum rating of 80% are required to remove tobacco smokeeffectively Filters with 80% or higher efficiency are also recom-mended for those facilities having particularly expensive interiordecor Because of the few operating hours of these facilities, theadded expense of higher-efficiency filters can be justified by theirlonger life Low-efficiency prefilters are generally used with high-efficiency filters to extend their useful life Ionization and chemi-cally reactive filters should be considered where high concentra-tions of smoke or odors are present

Noise and Vibration Control

The desired noise criteria (NC) vary with the type and quality ofthe facility The need for noise control may be minimal in a gymna-sium or natatorium, but it is important in a concert hall Facilitiesthat are used for varied functions require noise control evaluationover the entire spectrum of use

In most cases, sound and vibration control is required for bothequipment and duct systems, as well as in the selection of diffusersand grilles When designing a performance theater or concert hall,

an experienced acoustics engineer should be consulted In these

The preparation of this chapter is assigned to TC 9.8, Large Building

Air-Conditioning Applications.

Copyright © 2003, ASHRAE

projects, the quantity and quality or characteristic of the noise is

very important

Transmission of vibration and noise can be decreased by

mount-ing pipes, ducts, and equipment on a separate structure independent

of the music hall If the mechanical equipment space is close to the

music hall, the entire mechanical equipment room may need to be

floated on isolators, including the floor slab, structural floor

mem-bers, and other structural elements such as supporting pipes or

sim-ilar materials that can carry vibrations Properly designed inertia

pads are often used under each piece of equipment The equipment

is then mounted on vibration isolators

Manufacturers of vibration isolating equipment have devised

methods to float large rooms and entire buildings on isolators

Where subway and street noise may be carried into the structure of

a music hall, it is necessary to float the entire music hall on isolators

If the music hall is isolated from outside noise and vibration, it also

must be isolated from mechanical equipment and other internal

noise and vibrations

External noise from mechanical equipment such as cooling

tow-ers should not enter the building Care should be taken to avoid

designs that permit noises to enter the space through air intakes or

reliefs and carelessly designed duct systems

Ancillary Facilities

Ancillary facilities are generally a part of any assembly building;

almost all have some office space Convention centers and many

auditoriums, arenas, and stadiums have restaurants and cocktail

lounges Churches may have apartments for the clergy or a school

Many facilities have parking structures These varied ancillary

facil-ities are discussed in other chapters of this volume However, for

reasonable operating economy, these facilities should be served by

separate systems when their hours of use differ from those of the

main assembly areas

Air Conditioning

Because of their characteristic large size and need for considerable

ventilation air, assembly buildings are frequently served by

single-zone or variable-volume systems providing 100% outdoor air

Sepa-rate air-handling units usually serve each zone, although multizone,

dual-duct, or reheat types can also be applied with lower operating

efficiency In larger facilities, separate zones are generally provided

for the entrance lobbies and arterial corridors that surround the

seat-ing space Low-intensity radiant heatseat-ing is often an efficient

alterna-tive In some assembly rooms, folding or rolling partitions divide the

space for different functions, so a separate zone of control for each

resultant space is best In extremely large facilities, several

air-han-dling systems may serve a single space, due to the limits of equipment

size and also for energy and demand considerations

Peak Load Reduction

There are several techniques currently in use to help address peak

loads Thermal storage is discussed in Chapter 34 Another popular

technique, precooling, can be managed by the building operator

Pre-cooling the building mass several degrees below the desired indoor

temperature several hours before it is occupied allows it to absorb a

part of the peak heat load This cooling reduces the equipment size

needed to meet short-term loads The effect can be used if cooling

time of at least 1 h is available prior to occupancy, and then only when

the period of peak load is relatively short (2 h or less)

The designer must advise the owner that the space temperature

will be cold to most people as occupancy begins, but will warm up

as the performance progresses; this should be understood by all

con-cerned before proceeding with a precooling concept Precooling

works best when the space is used only occasionally during the

hot-ter part of the day and when provision of full capacity for an

occa-sional purpose is not economically justifiable

Stratification

Because most assembly buildings have relatively high ceilings,some heat may be allowed to stratify above the occupied zone,thereby reducing the load on the equipment Heat from lights can bestratified, except for the radiant portion (about 50% for fluorescentand 65% for incandescent or mercury-vapor fixtures) Similarly,only the radiant effect of the upper wall and roof load (about 33%)reaches the occupied space Stratification only occurs when air isadmitted and returned at a sufficiently low elevation so that it doesnot mix with the upper air Conversely, stratification may increaseheating loads during periods of minimal occupancy in winter Inthese cases, ceiling fans, air-handling systems, or high/low air dis-tribution may be desirable to reduce stratification Balconies mayalso be affected by stratification and should be well ventilated

Air Distribution

In assembly buildings, people generally remain in one placethroughout a performance, so they cannot avoid drafts Therefore,good air distribution is essential

Heating is seldom a major problem, except at entrances or ing warm-up before occupancy Generally, the seating area is iso-lated from the exterior by lobbies, corridors, and other ancillaryspaces For cooling, air can be supplied from the overhead space,where it mixes with heat from the lights and occupants Return airopenings can also aid air distribution Air returns located belowseating or at a low level around the seating can effectively distrib-ute air with minimum drafts; however, register velocities in excess

dur-of 1.4 m/s may cause objectionable drafts and noise

Because of the configuration of these spaces, supply jet nozzleswith long throws of 15 to 45 m may need to be installed on side-walls For ceiling distribution, downward throw is not critical pro-vided returns are low This approach has been successful inapplications that are not particularly noise-sensitive, but thedesigner needs to select air distribution nozzles carefully

The air-conditioning systems must be quiet This is difficult toachieve if the supply air is expected to travel 9 m or more from side-wall outlets to condition the center of the seating area Due to thelarge size of most houses of worship, theaters, and halls, high airdischarge velocities from the wall outlets are required These highvelocities can produce objectionable noise levels for people sittingnear the outlets This can be avoided if the return air system doessome of the work The supply air must be discharged from the airoutlet (preferably at the ceiling) at the highest velocity consistentwith an acceptable noise level Although this velocity does not allowthe conditioned air to reach all seats, the return air registers, whichare located near seats not reached by the conditioned air, pull the air

to cool or heat the audience, as required In this way, the supply airblankets the seating area and is pulled down uniformly by the returnair registers under or beside the seats

A certain amount of exhaust air should be taken from the ceiling

of the seating area, preferably over the balcony (if there is one) toprevent pockets of hot air, which can produce a radiant effect andcause discomfort, as well as increase the cost of air conditioning

Where the ceiling is close to the audience (e.g., below balconies andmezzanines), specially designed plaques or air-distributing ceilingsshould be provided to absorb noise

Regular ceiling diffusers placed more than 9 m apart normallygive acceptable results if careful engineering is applied in theselection of the diffusers Because large air quantities are generallyinvolved and because the building is large, fairly large capacitydiffusers, which tend to be noisy, are frequently selected Lineardiffusers are more acceptable architecturally and perform well ifselected properly Integral dampers in diffusers should not be used

as the only means of balancing because they generate intolerableamounts of noise, particularly in larger diffusers

Mechanical Equipment Rooms

The location of mechanical and electrical equipment rooms

affects the degree of sound attenuation treatment required Those

located near the seating area are more critical because of the normal

attenuation of sound through space Those near the stage area are

critical because the stage is designed to project sound to the

audi-ence If possible, mechanical equipment rooms should be in an area

separated from the main seating or stage area by buffers such as

lob-bies or service areas The economies of the structure, attenuation,

equipment logistics, and site must be considered in selecting

loca-tions for mechanical equipment rooms

At least one mechanical equipment room is placed near the roof

to house the toilet exhaust, general exhaust, cooling tower, kitchen,

and emergency stage exhaust fans, if any Individual roof-mounted

exhaust fans may be used, thus eliminating the need for a

ical equipment room However, to reduce sound problems,

mechan-ical equipment should not be located on the roof over the music hall

or stage but rather over offices, storerooms, or auxiliary areas

HOUSES OF WORSHIP

Houses of worship seldom have full or near-full occupancy more

than once a week, but they have considerable use for smaller

func-tions (meetings, weddings, funerals, christenings, or daycare)

throughout the rest of the week It is important to determine how and

when the building will be used When thermal storage is used,

longer operation of equipment prior to occupancy may be required

due to the high thermal mass of the structure The seating capacity

of houses of worship is usually well defined Some houses of

wor-ship have a movable partition to form a single large auditorium for

special holiday services It is important to know how often this

max-imum use is expected

Houses of worship test a designer’s ingenuity in locating

equip-ment and air diffusion devices in architecturally acceptable places

Because occupants are often seated, drafts and cold floors should be

avoided Many houses of worship have a high vaulted ceiling, which

creates thermal stratification Where stained glass is used, a shade

coefficient equal to solar glass (SC = 0.70) is assumed

Houses of worship may also have auxiliary rooms that should be

air conditioned To ensure privacy, sound transmission between

adjacent areas should be considered in the air distribution scheme

Diversity in the total air-conditioning load requirements should be

evaluated to take full advantage of the characteristics of each area

In houses of worship, it is desirable to provide some degree of

individual control for the platform, sacristy, and bema or choir area

AUDITORIUMS

The types of auditoriums considered are movie theaters,

play-houses, and concert halls Auditoriums in schools and the large

auditoriums in some convention centers may follow the same

prin-ciples, with varying degrees of complexity

Movie Theaters

Motion picture theaters are the simplest of the auditorium

struc-tures mentioned here They run continuously for periods of 4 to 8 h

or more and, thus, are not a good choice for precooling techniques,

except for the first matinee peak They operate frequently at low

occupancy levels, and low-load performance must be considered

Additionally, they tend to have lower sensible heat factors; special

care must be taken to ensure proper relative humidity levels can be

maintained without overcooling the space

Motion picture sound systems make noise control less important

than it is in other kinds of theaters The lobby and exit passageways

in a motion picture theater are seldom densely occupied, although

some light to moderate congestion can be expected for short times

in the lobby area A reasonable design for the lobby space is one son per 1.8 to 2.8 m2

per-The lights are usually dimmed when the house is occupied; fulllighting intensity is used only during cleaning A reasonable valuefor lamps above the seating area during a performance is 5 to 10%

of the installed wattage Designated smoking areas should be dled with separate exhaust or air-handling systems to avoid contam-ination of the entire facility

han-Projection Booths The projection booth represents the major

problem in motion picture theater design For large theaters usinghigh-intensity lamps, projection room design must follow appli-cable building codes If no building code applies, the projectionequipment manufacturer usually has specific requirements Theprojection room may be air conditioned, but it is normally exhausted

or operated at negative pressure Exhaust is normally taken throughthe housing of the projectors Additional exhaust is required for theprojectionist’s sanitary facilities Other heat sources include soundand dimming equipment, which require a continuously controlledenvironment and necessitate a separate system

Smaller theaters have fewer requirements for projection booths

It is a good idea to condition the projection room with filtered ply air to avoid soiling lenses In addition to the projector light, heatsources in the projection room include the sound equipment, as well

sup-as the dimming equipment

appli-• Performance theaters generally play to a full or near-full house

• Performance theaters usually have intermissions, and the lobbyareas are used for drinking and socializing The intermissions areusually relatively short, seldom exceeding 15 to 20 min; however,the load may be as dense as one person per 0.5 m2

• Because sound amplification is less used than that in motion ture theaters, background noise control is more important

pic-• Stage lighting contributes considerably to the total cooling load inperformance theaters Lighting loads can vary from performance

to performance

Stages The stage presents the most complex problem It consists

of the following loads:

• A heavy, mobile lighting load

• Intricate or delicate stage scenery, which varies from scene toscene and presents difficult air distribution requirements

• Actors, who may perform tasks that require exertionApproximately 40 to 60% of the lighting load can be eliminated

by exhausting air around the lights This procedure works for lightsaround the proscenium However, it is more difficult to placeexhaust air ducts directly above lights over the stage because of thescenery and light drops Careful coordination is required to achieve

an effective and flexible layout

Conditioned air should be introduced from the low side andback stages and returned or exhausted around the lights Someexhaust air must be taken from the top of the tower directly overthe stage containing lights and equipment (i.e., the fly) The airdistribution design is further complicated because pieces of scen-ery may consist of light materials that flutter in the slightest aircurrent Even the vertical stack effect created by the heat fromlights may cause this motion Therefore, low air velocities areessential and air must be distributed over a wide area with numer-ous supply and return registers

With multiple scenery changes, low supply or return registers

from the floor of the stage are almost impossible to provide

How-ever, some return air at the footlights and for the prompter should be

considered Air conditioning should also be provided for the stage

manager and the control board areas

One phenomenon encountered in many theaters with overhead

flies is the billowing of the stage curtain when it is down This is

pri-marily due to the stack effect created by the height of the main stage

tower, the heat from the lights, and the temperature difference

between the stage and seating areas Proper air distribution and

bal-ancing can minimize this phenomenon Bypass damper

arrange-ments with suitable fire protection devices may be feasible

Loading docks adjacent to stages located in cold climates

should be heated The doors to these areas may be open for long

periods, for example, while scenery is being loaded or unloaded

for a performance

On the stage, local code requirements must be followed for

emer-gency exhaust ductwork or skylight (or blow-out hatch)

require-ments These openings are often sizable and should be incorporated

in the early design concepts

Concert Halls

Concert halls and music halls are similar to legitimate theaters

They normally have a full stage, complete with fly gallery, and

dressing areas for performers Generally, the only differences

between the two are in size and decor, with the concert hall usually

being larger and more elaborately decorated

Air-conditioning design must consider that the concert hall is

used frequently for special charity and civic events, which may be

preceded by or followed by parties (and may include dancing) in the

lobby area Concert halls often have cocktail lounge areas that

become very crowded, with heavy smoking during intermissions

These areas should be equipped with flexible exhaust-recirculation

systems Concert halls may also have full restaurant facilities

As in theatres, noise control is important The design must

avoid characterized or narrow-band noises in the level of

audibil-ity Much of this noise is structure-borne, resulting from

inade-quate equipment and piping vibration isolation An experienced

acoustical engineer is essential for help in the design of these

applications

ARENAS AND STADIUMS

Functions at arenas and stadiums may be quite varied, so the

air-conditioning loads will vary Arenas and stadiums are not only used

for sporting events such as basketball, ice hockey, boxing, and track

meets but may also house circuses; rodeos; convocations; social

affairs; meetings; rock concerts; car, cycle, and truck events; and

special exhibitions such as home, industrial, animal, or sports

shows For multipurpose operations, the designer must provide

highly flexible systems High-volume ventilation may be

satisfac-tory in many instances, depending on load characteristics and

out-side air conditions

Load Characteristics

Depending on the range of use, the load may vary from a very

low sensible heat ratio for events such as boxing to a relatively high

sensible heat ratio for industrial exhibitions Multispeed fans often

improve the performance at these two extremes and can aid in sound

control for special events such as concerts or convocations When

using multispeed fans, the designer should consider the

perfor-mance of the air distribution devices and cooling coils when the fan

is operating at lower speeds

Because total comfort cannot be ensured in an all-purpose

facil-ity, the designer must determine the level of discomfort that can be

tolerated, or at least the type of performances for which the facility

is primarily intended

As with other assembly buildings, seating and lighting tions are the most important load considerations Boxing events, forexample, may have the most seating, because the boxing ring area isvery small For the same reason, however, the area that needs to beintensely illuminated is also small Thus, boxing matches may rep-resent the largest latent load situation Other events that presentlarge latent loads are rock concerts and large-scale dinner dances,although the audience at a rock concert is generally less concernedwith thermal comfort Ventilation is also essential in removingsmoke or fumes at car, cycle, and truck events Circuses, basketball,and hockey have a much larger arena area and less seating The sen-sible load from lighting the arena area does improve the sensibleheat ratio The large expanse of ice in hockey games represents aconsiderable reduction in both latent and sensible loads High latentloads caused by occupancy or ventilation can create severe prob-lems in ice arenas such as condensation on interior surfaces and fog

combina-Special attention should be paid to the ventilation system, air bution, humidity control, and construction materials

distri-Enclosed Stadiums

An enclosed stadium may have either a retractable or a fixedroof When the roof is closed, ventilation is needed, so ductworkmust be run in the permanent sections of the stadium The large airvolumes required and the long air throws make proper air distribu-tion difficult to achieve; thus, the distribution system must be veryflexible and adjustable

Some open stadiums have radiant heating coils in the floor slabs

of the seating areas Gas-fired or electric high- or low-intensity ant heating located above the occupants is also used

radi-Open racetrack stadiums may present a ventilation problem if thegrandstand is enclosed The grandstand area may have multiple lev-els and be in the range of 400 m long and 60 m deep The interior(ancillary) areas must be ventilated to control odors from toiletfacilities, concessions, and the high population density Generalpractice provides about four air changes per hour for the stand seat-ing area and exhausts the air through the rear of the service areas

More efficient ventilation systems may be selected if architecturalconsiderations permit Fogging of windows is a winter concern withglass-enclosed grandstands This can be minimized by double glaz-ing, humidity control, moving dry air across the glass, or a radiantheating system for perimeter glass areas

Air-supported structures require the continuous operation of afan to maintain a properly inflated condition The possibility of con-densation on the underside of the air bubble should be considered

The U-factor of the roof should be sufficient to prevent tion at the lowest expected ambient temperature Heating and air-conditioning functions can be either incorporated into the inflatingsystem or furnished separately Solar and radiation control is alsopossible through the structure’s skin Applications, though increas-ing rapidly, still require working closely with the enclosure manu-facturer to achieve proper and integrated results

condensa-Ancillary Spaces

The concourse areas of arenas and stadiums are heavily lated during entrance, exit, and intermission periods Consider-able odor is generated in these areas by food, drink, and smoke,requiring considerable ventilation If energy conservation is animportant factor, carbon filters and controllable recirculationrates should be considered Concourse area air systems should beconsidered for their flexibility of returning or exhausting air Theeconomics of this type of flexibility should be evaluated with re-gard to the associated problem of air balance and freeze-up incold climates

popu-Ticket offices, restaurants, and similar facilities are often pected to be open during hours that the main arena is closed; there-fore, separate systems should be considered for these areas

Locker rooms require little treatment other than excellent

ven-tilation, usually not less than 10 to 15 L/s per square metre To

reduce the outdoor air load, excess air from the main arena or

sta-dium may be transferred into the locker rooms However, reheat

or recooling by water or primary air should be considered to

maintain the locker room temperature To maintain proper air

bal-ance under all conditions, locker rooms should have separate

sup-ply and exhaust systems

Ice Rinks

Refer to Chapter 34 of the ASHRAE Handbook—Refrigeration

for ice sheet design information When an ice rink is designed into

the facility, the concerns of groundwater conditions, site drainage,

structural foundations, insulation, and waterproofing become even

more important, with the potential of freezing of soil or fill under the

floor and subsequent expansion The rink floor may have to be

strong enough to support heavy trucks The floor insulation also

must be strong enough to take this load Ice-melting pits of

suffi-cient size with steam pipes may have to be furnished If the arena is

to be air conditioned, the possibility of combining the

air-condition-ing system with the ice rink system may be analyzed The designer

should be aware that both systems operate at vastly different

tem-peratures and may operate at different capacity levels at any given

time The radiant effects of the ice on the people and of the heat from

the roof and lights on the ice must be considered in the design and

operation of the system Also, low air velocity at the floor is related

to minimizing the refrigeration load High air velocities will cause

moisture to be drawn from the air by the ice sheet

Fog is formed when moisture-laden air is allowed to cool below

its dew point This is most likely to occur close to the ice surface

within the boarded area (playing area) Fog can be controlled by

reducing the indoor dew point with a dehumidification system or

high-latent-capacity air-conditioning system and by delivering

appropriate air velocities to bring the air in contact with the ice

Air-conditioning systems have had limited success in reducing the

dew-point temperature sufficiently to prevent fog

The type of lighting used over ice rinks must be carefully

con-sidered when precooling is used before hockey games and between

periods Main lights should be capable of being turned off, if

feasi-ble Incandescent lights require no warm-up time and are more

applicable than types requiring warm-up Low-emissivity ceilings

with reflective characteristics successfully reduce condensation on

roof structures; they also reduce lighting requirements

Gymnasiums

Smaller gymnasiums, such as those in school buildings, are

min-iature versions of arenas and often have multipurpose features For

further information, see Chapter 6, Educational Facilities

Many school gymnasiums are not air conditioned Low-intensity

perimeter radiant heaters with central ventilation supplying four to

six air changes per hour are effective and energy efficient Unit

heat-ers located at the ceiling are also effective Ventilation must be

pro-vided due to high activity levels and resulting odors

Most gymnasiums are located in schools However, public and

private organizations and health centers may also have

gymnasi-ums During the day, gymnasiums are usually used for physical

activities, but in the evening and on weekends, they may be used for

sports events, social affairs, or meetings Thus, their activities fall

within the scope of those of a civic center More gymnasiums are

being considered for air conditioning to make them more suitable

for civic center activities Design criteria are similar to arenas and

civic centers when used for such activities However, for schooltime

use, space temperatures are often kept between 18 and 20°C during

the heating season Occupancy and the degree of activity during

daytime use does not usually require high quantities of outdoor air,

but if used for other functions, system flexibility is required

CONVENTION AND EXHIBITION CENTERS

Convention-exhibition centers schedule diverse functions similar

to those at arenas and stadiums and present a unique challenge to thedesigner The center generally is a high-bay, long-span space Thesecenters can be changed weekly, for example, from an enormous com-puter room into a gigantic kitchen, large machine shop, departmentstore, automobile showroom, or miniature zoo They can also be thesite of gala banquets or used as major convention meeting rooms.The income earned by these facilities is directly affected by thetime it takes to change from one activity to the next, so highly flex-ible utility distribution and air-conditioning equipment are needed.Ancillary facilities include restaurants, bars, concession stands,parking garages, offices, television broadcasting rooms, and multi-ple meeting rooms varying in capacity from small (10 to 20 people)

to large (hundreds or thousands of people) Often, an appropriatelysized full-scale auditorium or arena is also incorporated

By their nature, these facilities are much too large and diverse intheir use to be served by a single air-handling system Multiple airhandlers with several chillers can be economical

Load Characteristics

The main exhibition room is subject to a variety of loads,depending on the type of activity in progress Industrial showsprovide the highest sensible loads, which may have a connectedcapacity of 215 W/m2 along with one person per 3.7 to 4.6 m2.Loads of this magnitude are seldom considered because largepower-consuming equipment is seldom in continuous operation

at full load An adequate design accommodates (in addition tolighting load) about 108 W/m2 and one person per 3.7 to 4.6 m2 as

a maximum continuous load

Alternative loads that are very different in character may beencountered When the main hall is used as a meeting room, the loadwill be much more latent in character Thus, multispeed fans orvariable-volume systems may provide a better balance of load dur-ing these high-latent, low-sensible periods of use The determina-tion of accurate occupancy and usage information is critical in anyplan to design and operate such a facility efficiently and effectively

System Applicability

The main exhibition hall is normally handled by one or more air systems This equipment should be capable of operating on alloutdoor air, because during set-up time, the hall may contain a num-ber of highway-size trucks bringing in or removing exhibit materi-als There are also occasions when the space is used for equipmentthat produces an unusual amount of fumes or odors, such as restau-rant or printing industry displays It is helpful to build some fluesinto the structure to duct fumes directly to the outside Perimeterradiant ceiling heaters have been successfully applied to exhibitionhalls with large expanses of glass

all-Smaller meeting rooms are best conditioned either with ual room air handlers, or with variable-volume central systems,because these rooms have high individual peak loads but are notused frequently Constant-volume systems of the dual- or single-duct reheat type waste considerable energy when serving emptyrooms, unless special design features are incorporated

individ-Offices and restaurants often operate for many more hours thanthe meeting areas or exhibition areas and should be served sepa-rately Storage areas can generally be conditioned by exhaustingexcess air from the main exhibit hall through these spaces

NATATORIUMS Environmental Control

A natatorium requires year-round humidity levels between 40and 60% for comfort, energy consumption, and building protec-tion The designer must address the following concerns: humidity

control, ventilation requirements for air quality (outdoor and

exhaust air), air distribution, duct design, pool water chemistry,

and evaporation rates A humidity control system will not provide

satisfactory results if any of these items are overlooked

Humidity Control

Humans are very sensitive to relative humidity Fluctuations in

relative humidity outside the 40 to 60% range can increase levels of

bacteria, viruses, fungi and other factors that reduce air quality For

swimmers, 50 to 60% rh is most comfortable High relative

humid-ity levels are destructive to building components Mold and mildew

can attack wall, floor, and ceiling coverings, and condensation can

degrade many building materials In the worst case, the roof could

collapse due to corrosion from water condensing on the structure

Load Estimation

Loads for a natatorium include building heat gains and losses

from outdoor air, lighting, walls, roof, and glass Internal latent

loads are generally from people and evaporation Evaporation loads

in pools and spas are significant relative to other load elements and

may vary widely depending on pool features, the areas of water and

wet deck, water temperature, and activity level in the pool

Evaporation The rate of evaporation can be estimated from

empirical Equation (1) This equation is valid for pools at normal

activity levels, allowing for splashing and a limited area of wetted

deck Other pool uses may have more or less evaporation (Smith et

al 1993)

(1)

where

w p= evaporation of water, kg/s

A = area of pool surface, m2

V = air velocity over water surface, m/s

Y = latent heat required to change water to vapor at

surface water temperature, kJ/kg

p a= saturation pressure at room air dew point, kPa

p w = saturation vapor pressure taken at surface water

temperature, kPa

The units for the constant 0.089 are W/(m2·Pa) The units for the

constant 0.0782 are W·s/(m3·Pa).

Equation (1) may be modified by multiplying it by an activity

factor F a to alter the estimate of evaporation rate based on the level

of activity supported For Y values of about 2400 kJ/kg and V values

ranging from 0.05 to 0.15 m/s, Equation (1) can be reduced to

w p = 4 × 10−5 A( p

The following activity factors should be applied to the areas of

specific features, and not to the entire wetted area:

The effectiveness of controlling the natatorium environment

depends on the correct estimation of water evaporation rates

Apply-ing the correct activity factors is extremely important in determinApply-ing

water evaporation rates The difference in peak evaporation rates

between private pools and active public pools of comparable size

may be more than 100%

Actual operating temperatures and relative humidity conditionsshould be established before design How the area will be used usu-ally dictates design The elderly prefer significantly warmer operat-ing temperatures than those listed Table 1

Air temperatures in public and institutional pools should bemaintained 1 to 2 K above the water temperature (but not above thecomfort threshold of 30°C) to reduce the evaporation rate and avoidchill effects on swimmers

Ventilation Requirements

Air Quality Outdoor air ventilation rates prescribed by

ASHRAE Standard 62 are intended to provide acceptable air

qual-ity conditions for the average pool using chlorine for its primary infection process The ventilation requirement may be excessive forprivate pools and installations with low use They may also proveinadequate for high occupancy public installations

dis-Air quality problems in pools and spas are caused by water ity problems, so simply increasing ventilation rates may prove bothexpensive and ineffective Water quality conditions are a directfunction of pool use and the type and effectiveness of the water dis-infection process used

qual-Because indoor pools usually have high ceilings, temperaturestratification can have a detrimental effect on indoor air quality

Careful duct layout must ensure that the space receives proper airchanges and homogeneous air quality throughout Some air move-ment at the deck and pool water level is essential to ensure accept-able air quality Complaints from swimmers indicate that thegreatest chloramine (see the section on Pool Water Chemistry) con-centrations occur at the water surface Children are especially vul-nerable to chloramine poisoning

Exhaust air from pools is rich in moisture and may contain highlevels of chloramine compounds While most codes permit pool air

to be used as makeup for showers, toilets, and locker rooms, thesespaces should be provided with separate ventilation and maintained

at a positive pressure with respect to the pool

Pool and spa areas should be maintained at a negative pressure

of 15 to 40 Pa relative to adjacent areas of the building to preventmoisture and chloramine odor migration Active methods of pres-sure control may prove more effective than static balancing andmay be necessary where outdoor air is used as a part of an activehumidity control strategy Openings from the pool to other areasshould be minimized and controlled Passageways should beequipped with doors with automatic closers to inhibit migration ofmoisture and air

Exhaust air intake grilles should be located as close as possible tothe warmest water in the facility Installations with intakes directlyabove whirlpools have resulted in the best air quality

Air Delivery Rates Total airflow should be determined by a

psychrometric analysis Most codes require a minimum of six (6) airchanges per hour, except where mechanical cooling is used Thisrate may prove inadequate for some occupancy and use

Where mechanical cooling is provided, air delivery rates should

be established to maintain appropriate conditions of temperatureand humidity The following rates are typically desired:

Type of Pool Typical Activity Factor (F a)

Type of Pool

Air Temperature,

°C

Water Temperature,

°C

Relative Humidity, %

Pools with no spectator areas 4 to 6 air changes per hour

Spectator areas 6 to 8 air changes per hour

Therapeutic pools 4 to 6 air changes per hour

Outdoor air delivery rates may be constant or variable,

depend-ing on the design Minimum rates, however, must provide adequate

dilution of contaminants generated by pool water and must maintain

acceptable ventilation for occupancy

Where a minimum outdoor air ventilation rate is established to

protect against condensation in a building’s structural elements, the

rates are typically used for 100% outdoor air systems These rates

usually result in excessive humidity levels under most operating

conditions and are generally not adequate to produce acceptable

indoor air quality, especially in public facilities subject to heavy use

Duct Design

As with any installation, proper duct design and installation is

necessary for proper equipment performance Poorly installed

return duct connections, for example, can significantly reduce the

performance of a dehumidifier The following duct construction

practices apply to natatoriums:

• Fiberglass duct liner should not be used Where condensation may

occur, the insulation must be applied to the exterior of the duct

• Duct materials and hardware must be resistant to chemical

corro-sion from the pool atmosphere The 400 series stainless steels are

readily attacked by chlorides in moist environments The 316

series stainless steel, painted galvanized, fabric (with appropriate

grilles sewn in), or aluminum sheet metal may be used for exposed

duct systems Buried ductwork should be constructed from

non-metallic fiberglass-reinforced or PVC materials due to the

diffi-culty of replacing damaged materials

• Grilles, registers, and diffusers should be constructed from

alumi-num They should be selected for low static pressure loss and for

appropriate throws for proper air distribution

• Supply air should be directed against interior envelope surfaces

prone to condensation (walls, glass, and doors) A portion of the

supply air should be directed over the water surface to move

con-taminated air toward an exhaust point and control chloramines

released at the water surface

• Return air inlets should be located to recover the warm humid air

and return it to the ventilation system for treatment, to prevent the

supply air from short-circuiting, and minimize recirculation of

chloramines

• Exhaust air inlets should be located to maximize capture

effec-tiveness and minimize the recirculation of chloramines

Exhaust-ing from directly above whirlpools is also desirable Exhaust air

should be taken directly to the outside, through heat recovery

devices where provided

• Filtration should be selected to provide 45 to 65% efficiencies (as

defined in ASHRAE Standard 52.1) and be installed in locations

selected to prevent condensation in the filter bank Filter media

and support materials should be resistant to moisture degradation

• Air systems may be designed for noise levels of NC 45-50;

how-ever, wall, floor, and ceiling surfaces should be evaluated for their

attenuation effect

Envelope Design

Glazing in exterior walls becomes susceptible to condensation

when the outdoor temperature drops below the pool room dew

point The design goal is to maintain the surface temperature of the

glass and the window frames a minimum of 3 K above the pool

room dew point Windows must allow unobstructed air movement

on inside surfaces Thermal break frames should be used Recessed

windows and protruding window frames should be avoided

Sky-lights are especially vulnerable and attention should be given to

control condensation on them Wall and roof vapor retarder designs

should be carefully reviewed, especially at to-wall and to-roof junctures and at window, door, and duct penetrations Thepool enclosure must be suitable for year-round operation at 50 to60% relative humidity A vapor barrier analysis (as in Figure 10

wall-in Chapter 23 of the ASHRAE Handbook—Fundamentals) should

be prepared Failure to install an effective vapor retarder will result

in condensation forming in the structure and potentially seriousdamage

Pool Water Chemistry

Failure to maintain proper chemistry in the pool water causesserious air quality problems and deterioration of mechanical andbuilding systems Water treatment equipment should be installed in

a separate, dedicated, well-ventilated space that is under negativepressure Pool water treatment consists of primary disinfection, pHcontrol, water filtration and purging, and water heating For furtherinformation, refer to Kowalsky (1990)

Air quality problems are usually caused by the reaction of rine with biological wastes, and particularly with ammonia, which

chlo-is a by-product of the breakdown of urine and perspiration Chlorinereacts with these wastes, creating chloramines (monochloramine,dichloramine, and nitrogen trichloride) that are commonly mea-sured as combined chlorine The addition of chemicals to pool waterincreases total contaminant levels In high-occupancy pools, watercontaminant levels can double in a single day of operation.The reduction of ammonia by chlorine is affected by several fac-tors including water temperature, water pH, total chlorine concen-tration, and the level of dissolved solids in the water Because oftheir higher operating temperature and higher ratio of occupancyper unit water volume, spas produce greater quantities of air con-taminants than pools

The following measures have demonstrated a potential to reducechloramine concentrations in the air and water:

• Ozonation In low concentrations, ozone has substantially

reduced the concentration of combined chlorine in the water Inhigh concentrations, ozone can replace chlorine as the primarydisinfection process; however, ozone is unable to maintain suffi-cient residual levels in the water to maintain a latent biocidaleffect This necessitates the maintenance of chlorine as a residualprocess at concentrations of 0.5 to 1.5 mg/kg

• Water Exchange Rates High concentrations of dissolved solids

in water have been shown to directly contribute to high combinedchlorine (chloramine) levels Adequate water exchange rates arenecessary to prevent the buildup of biological wastes and their oxi-dized components in pool and spa water Conductivity measure-ment is an effective method to control the exchange rate of water

in pools and spas to effectively maintain water quality and mize water use In high-occupancy pools, heat recovery may proveuseful in reducing water heating energy requirements

mini-Energy Considerations

Natatoriums can be major energy burden on facilities, so theyrepresent a significant opportunity for energy conservation Severaldesign solutions are possible using both dehumidification and ven-tilation strategies When evaluating a system, the energy consumed

by all elements should be considered, including primary heating andcooling systems, fan motors, water heaters, and pumps

Natatoriums with fixed outdoor air ventilation rates without midification generally have seasonally fluctuating space temperatureand humidity levels Systems designed to provide minimum ventila-tion rates without dehumidification are unable to maintain relativehumidity conditions within prescribed limits These systems mayfacilitate mold and mildew growth and may be unable to provideacceptable indoor air quality Peak dehumidification loads vary withactivity levels and during the cooling season when ventilation airbecomes an additional dehumidification load to the space

FAIRS AND OTHER TEMPORARY EXHIBITS

Occasionally, large-scale exhibits are constructed to stimulate

business, present new ideas, and provide cultural exchanges Fairs

of this type take years to construct, are open from several months to

several years, and are sometimes designed considering future use of

some of the buildings Fairs, carnivals, or exhibits, which may

con-sist of prefabricated shelters and tents that are moved from place to

place and remain in a given location for only a few days or weeks,

are not covered here because they seldom require the involvement of

architects and engineers

Design Concepts

One consultant or agency should be responsible for setting

uni-form utility service regulations and practices to ensure proper

orga-nization and operation of all exhibits Exhibits that are open only

during spring or fall months require a much smaller heating or

cool-ing plant than those open durcool-ing peak summer or winter months

This information is required in the earliest planning stages so that

system and space requirements can be properly analyzed

Occupancy

Fair buildings have heavy occupancy during visiting hours, but

patrons seldom stay in any one building for a long period The

length of time that patrons stay in a building determines the

air-conditioning design The shorter the anticipated stay, the greater the

leeway in designing for less-than-optimum comfort, equipment, and

duct layout Also, whether patrons wear coats and jackets while in

the building influences operating design conditions

Equipment and Maintenance

Heating and cooling equipment used solely for maintaining

com-fort and not for exhibit purposes may be secondhand or leased, if

available and of the proper capacity Another possibility is to rent

the air-conditioning equipment to reduce the capital investment and

eliminate disposal problems when the fair is over

Depending on the size of the fair, the length of time it will

oper-ate, the types of exhibitors, and the policies of the fair sponsors, it

may be desirable to analyze the potential for a centralized heating

and cooling plant versus individual plants for each exhibit The

pro-portionate cost of a central plant to each exhibitor, including utility

and maintenance costs, may be considerably less than having to

fur-nish space and plant utility and maintenance costs The larger the

fair, the more savings may result It may be practical to make the

plant a showcase, suitable for exhibit and possibly added revenue A

central plant may also form the nucleus for the commercial or

indus-trial development of the area after the fair is over

If exhibitors furnish their own air-conditioning plants, it is

advis-able to analyze shortcuts that may be taken to reduce equipment

space and maintenance aids For a 6-month to 2-year maximum

operating period, for example, tube pull or equipment removal

space is not needed or may be drastically reduced Higher fan and

pump motor power and smaller equipment is permissible to save on

initial costs Ductwork and piping costs should be kept as low as

possible because these are usually the most difficult items to

sal-vage; cheaper materials may be substituted wherever possible The

job must be thoroughly analyzed to eliminate all unnecessary items

and reduce all others to bare essentials

The central plant may be designed for short-term use as well

However, if the plant is to be used after the fair closes, the central

plant should be designed in accordance with the best practice for

long-life plants It is difficult to determine how much of the piping

distribution system can be used effectively for permanent

installa-tions For that reason, piping should be simply designed initially,

preferably in a grid, loop, or modular layout, so that future additions

can be made easily and economically

Air Cleanliness

The efficiency of the filters needed for each exhibit is determined

by the nature of the area served Because the life of an exhibit is veryshort, it is desirable to furnish the least expensive filtering system Ifpossible, one set of filters should be selected to last for the life of theexhibit In general, the filtering efficiencies do not have to exceed

30% (see ASHRAE Standard 52.1).

System Applicability

If a central air-conditioning plant is not built, the equipmentinstalled in each building should be the least costly to install andoperate for the life of the exhibit These units and systems should bedesigned and installed to occupy the minimum usable space

Whenever feasible, heating and cooling should be performed byone medium, preferably air, to avoid running a separate piping andradiation system for heating and a duct system for cooling Air cur-tains used on an extensive scale may, on analysis, simplify the build-ing structure and lower total costs

Another possibility when both heating and cooling are required

is a heat pump system, which may be less costly than separate ing and cooling plants Economical operation may be possible,depending on the building characteristics, lighting load, and occu-pant load If well or other water is available, it may produce a moreeconomical installation than an air-source heat pump

heat-ATRIUMS

Atriums have diverse functions and occupancies An atrium may(1) connect buildings; (2) serve as an architectural feature, leisurespace, greenhouse, and/or smoke reservoir; and (3) afford energyand lighting conservation The temperature, humidity, and hours ofusage of an atrium are directly related to those of the adjacent build-ings Glass window walls and skylights are common Atriums aregenerally large in volume with relatively small floor areas The tem-perature and humidity conditions, air distribution, impact fromadjacent buildings, and fenestration loads to the space must be con-sidered in the design of an atrium

Perimeter radiant heating (e.g., overhead radiant type, wallfinned-tube or radiant type, floor radiant type, or combinationsthereof) is commonly used for the expansive glass windows and sky-lights Air-conditioning systems can heat, cool, and control smoke

The distribution of air across windows and skylights can also controlheat transfer and condensation Low supply and high return air dis-tribution can control heat stratification, as well as wind and stackeffects Some atrium designs include a combination of high/low sup-ply and high/low return air distribution to control heat transfer, con-densation, stratification, and wind/stack effects

The energy use of an atrium can be reduced by installing and triple-panel glass and mullions with thermal breaks, as well asshading devices such as external, internal, and interior screens,shades, and louvers

double-Extensive landscaping is common in atriums Humidity levelsare generally maintained between 10 and 35% Hot and cold airshould not be distributed directly onto plants and trees

Smith, C.C., R.W Jones, and G.O.G Löf 1993 Energy requirements and

potential savings for heated indoor swimming pools ASHRAE actions 99(2):864-874

Trans-Kowalsky, L., ed 1990 Pool/spa operators handbook National Swimming

Pool Foundation, Merrick, NY.

OTELS, motels, and dormitories may be single-room or

Hmultiroom, long- or short-term dwelling (or residence) units;

they may be stacked sideways and/or vertically Information in the

first three sections of the chapter applies generally; the last three

sections are devoted to the individual types of facilities

LOAD CHARACTERISTICS

1 Ideally each room served by an HVAC unit should be able to be

ventilated, cooled, heated, or dehumidified independently of any

other room If not, air conditioning for each room will be

com-promised

2 Typically, the space is not occupied at all times For adequate

flexibility, each unit’s ventilation and cooling should be able to

be shut off (except when humidity control is required), and its

heating to be shut off or turned down

3 Concentrations of lighting and occupancy are typically low;

activity is generally sedentary or light Occupancy is transient in

nature, with greater use of bedrooms at night

4 Kitchens, whether integrated with or separate from residential

quarters, have the potential for high appliance loads, odor

gen-eration, and large exhaust requirements

5 Rooms generally have an exterior exposure, kitchens, toilets, and

dressing rooms may not The building as a whole usually has

multiple exposures, as may many individual dwelling units

6 Toilet, washing, and bathing facilities are almost always

incor-porated in the dwelling units Exhaust air is usually incorincor-porated

in each toilet area

7 The building has a relatively high hot water demand, generally

for periods of an hour or two, several times a day This demand

can vary from a fairly moderate and consistent daily load profile

in a senior citizens building to sharp, unusually high peaks at

about 6:00 P.M in dormitories Chapter 49 includes details on

service water heating

8 Load characteristics of rooms, dwelling units, and buildings can

be well defined with little need to anticipate future changes to the

design loads, other than the addition of a service such as cooling

that may not have been incorporated originally

9 The prevalence of shifting, transient interior loads and exterior

exposures with glass results in high diversity factors; the

long-hour usage results in fairly high load factors

DESIGN CONCEPTS AND CRITERIA

Wide load swings and diversity within and between rooms

require the design of a flexible system for 24-hour comfort Besides

opening windows, the only method of providing flexible

tempera-ture control is having individual room components under individual

room control that can cool, heat, and ventilate independently of the

equipment in other rooms

In some climates, summer humidity becomes objectionablebecause of the low internal sensible loads that result when cooling

is on-off controlled Modulated cooling and/or reheat may berequired to achieve comfort Reheat should be avoided unless somesort of heat recovery is involved

Dehumidification can be achieved by lowering cooling coil peratures and reducing airflow Another means of dehumidification

tem-is desiccant dehumidifiers

Some people have a noise threshold low enough that certaintypes of equipment disturb their sleep Higher noise levels may beacceptable in areas where there is little need for air conditioning.Medium and better quality equipment is available with noise criteria(NC) 35 levels at 3 to 4 m in medium to soft rooms and little soundchange when the compressor cycles

Perimeter fan coils are usually quieter than unitary systems, butunitary systems provide more redundancy in case of failure

SYSTEMS Energy-Efficient Systems

The most efficient systems generally include water-source andair-source heat pumps In areas with ample solar radiation, water-source heat pumps may be solar assisted Energy-efficient equip-ment generally has the lowest operating cost and is relatively sim-ple, an important factor where skilled operating personnel areunlikely to be available Most systems allow individual operationand thermostatic control The typical system allows individualmetering so that most, if not all, of the cooling and heating costs can

be metered directly to the occupant (McClelland 1983) Existingbuildings can be retrofitted with heat flow meters and timers on fanmotors for individual metering

The water-loop heat pump has a lower operating cost than cooled unitary equipment, especially where electric heat is used.The lower installed cost encourages its use in mid- and high-risebuildings where individual dwelling units have floor areas of 75 m2

air-or larger Some systems incair-orpair-orate sprinkler piping as the waterloop

Except for the central circulating pump, heat rejector fans, andsupplementary heater, the water-loop heat pump is predominantlydecentralized; individual metering allows most of the operating cost

to be paid by the occupant Its life should be longer than for otherunitary systems because most of the mechanical equipment is in thebuilding and not exposed to outdoor conditions Also, the load onthe refrigeration circuit is not as severe because the water tempera-ture is controlled for optimum operation Operating costs are lowdue to the energy conservation inherent in the system Excess heatmay be stored during the day for the following night, and heat may

be transferred from one part of the building to another

While heating is required in many areas during cool weather,cooling may be needed in rooms having high solar or internal loads

On a mild day, surplus heat throughout the building is frequentlytransferred into the hot water loop by water-cooled condensers on

The preparation of this chapter is assigned to TC 9.8, Large Building

Air-Conditioning Applications.

Copyright © 2003, ASHRAE

cooling cycle so that water temperature rises The heat remains

stored in water from which it can be extracted at night; a water

heater is not needed This heat storage is improved by the presence

of a greater mass of water in the pipe loop; some systems include a

storage tank for this reason Because the system is designed to

oper-ate during the heating season with woper-ater supplied at a temperature as

low as 15°C, the water-loop heat pump lends itself to solar assist;

relatively high solar collector efficiencies result from the low water

temperature

The installed cost of the water-loop heat pump is higher in very

small buildings In severe cold climates with prolonged heating

sea-sons, even where natural gas or fossil fuels are available at

reason-able cost, the operating cost advantages of this system may diminish

unless heat can be recovered from some another source, such as

solar collectors, geothermal, or internal heat from a commercial

area served by the same system

Energy-Neutral Systems

Energy-neutral systems do not allow simultaneous cooling and

heating Some examples are (1) packaged terminal air conditioners

(PTACs) (through-the-wall units), (2) window units or radiant

ceil-ing panels for coolceil-ing combined with finned or baseboard radiation

for heating, (3) unitary air conditioners with an integrated heating

system, (4) fan coils with remote condensing units, and (5) variable

air volume (VAV) systems with either perimeter radiant panel

heat-ing or baseboard heatheat-ing To qualify as energy-neutral, a system

must have controls that prevent simultaneous operation of the

cool-ing and heatcool-ing cycles For unitary equipment, control may be as

simple as a heat-cool switch For other types, dead-band

thermo-static control may be required

PTACs are frequently installed to serve one or two rooms in

buildings with mostly small, individual units In a common

two-room arrangement, a supply plenum diverts a portion of the

condi-tioned air serving one room into the second, usually smaller, room

Multiple PTAC units allow additional zoning in dwellings having

more rooms Additional radiation heat is sometimes needed around

the perimeter in cold climates

Heat for a PTAC may be supplied either by electric resistance

heaters or by hot water or steam heating coils Initial costs are lower

for a decentralized system using electric resistance heat Operating

costs are lower for coils heated by combustion fuels Despite having

relatively inefficient refrigeration circuits, the operating cost of a

PTAC is quite reasonable, mostly because individual thermostatic

control each machine, which eliminates the use of reheat while

pre-venting the space from being overheated or overcooled Also,

because the equipment is located in the space being served, little

power is devoted to circulating the room air Servicing is simple—

a defective machine is replaced by a spare chassis and forwarded

to a service organization for repair Thus, building maintenance

requires relatively unskilled personnel

Noise levels are generally no higher than NC 40, but some units

are noisier than others Installations near a seacoast should be

specially constructed (usually with stainless steel or special

coat-ings) to avoid the accelerated corrosion to aluminum and steel

com-ponents caused by salt In high-rise buildings of more than 12

stories, special care is required, both in the design and construction

of outside partitions and in the installation of air conditioners, to

avoid operating problems associated with leakage (caused by stack

effect) around and through the machines

Frequently, the least expensive installation is finned or baseboard

radiation for heating and window-type room air conditioners for

cooling The window units are often purchased individually by the

building occupants This choice offers a reasonable operating cost

and is relatively simple to maintain However, window units have

the shortest equipment life, the highest operating noise level, and

the poorest distribution of conditioned air of any of the systems

dis-cussed in this section

Fan coils with remote condensing units are used in smaller ings Fan coil units are located in closets, and the ductwork distrib-utes air to the rooms in the dwelling Condensing units may belocated on roofs, at ground level, or on balconies

build-Low capacity residential warm air furnaces may be used for ing, but with gas- or oil-fired units, the products of combustion must

heat-be vented In a one- or two-story structure, it is possible to use vidual chimneys or flue pipes, but in a high-rise structure requires amultiple-vent chimney or a manifold vent Local codes should beconsulted

indi-Sealed combustion furnaces draw all the combustion air fromoutside and discharge the flue products through a windproof vent tothe outdoors The unit must be located near an outside wall, andexhaust gases must be directed away from windows and intakes Inone- or two-story structures, outdoor units mounted on the roof or

on a pad at ground level may also be used All of these heating unitscan be obtained with cooling coils, either built-in or add-on Evap-orative-type cooling units are popular in motels, low-rise apart-ments, and residences in mild climates

Desiccant dehumidification should be considered when pendent control of temperature and humidity is required to avoidreheat

inde-Energy-Inefficient Systems

Energy-inefficient systems allow simultaneous cooling and ing Examples include two-, three-, and four-pipe fan coil units, ter-minal reheat systems, and induction systems Some units, such asthe four-pipe fan coil, can be controlled so that they are energy-neutral They are primarily used for humidity control

heat-Four-pipe systems and two-pipe systems with electric heaterscan be designed for complete temperature and humidity flexibilityduring summer and intermediate season weather, although noneprovides winter humidity control Both systems provide full dehu-midification and cooling with chilled water, reserving the other twopipes or an electric coil for space heating or reheat The equipmentand necessary controls are expensive, and only the four-pipe sys-tem, if equipped with an internal-source heat-recovery design forthe warm coil energy, can operate at low cost When year-roundcomfort is essential, four-pipe systems or two-pipe systems withelectric heat should be considered

Total Energy Systems

A total energy system is an option for any multiple or largehousing facility with large year-round service water heating re-quirements Total energy systems are a form of cogeneration inwhich all or most electrical and thermal energy needs are met byon-site systems as described in Chapter 7 of the ASHRAE Hand-

book—HVAC Systems and Equipment A detailed load profilemust be analyzed to determine the merits of using a total energysystem The reliability and safety of the heat-recovery systemmust also be considered

Any of the previously described systems can perform the HVACfunction of a total energy system The major considerations as theyapply to total energy in choosing a HVAC system are as follows:

• Optimum use must be made of the thermal energy recoverablefrom the prime mover during all or most operating modes, not justduring conditions of peak HVAC demand

• Heat recoverable via the heat pump may become less usefulbecause the heat required during many of its potential operatinghours will be recovered from the prime mover The additionalinvestment for heat pump or heat recovery cycles may be moredifficult to justify because operating savings are lower

• The best application for recovered waste heat is for those servicesthat use only heat (i.e., service hot water, laundry facilities, andspace heating)