HVAC Systems Design Handbook part 13

But for projects of importance or great value where the work is accomplished by contract between owner and builder, it is important that there be good specifications in addition to the dr

Design Documentation: Drawings and Specifications

13.1 Introduction

Design documents evolve from and include the designer’s calculations, equipment selections, and sketches and are usually presented through formal drawings and specifications These construction documents are the legal means by which the designer conveys the owner’s expecta-tions to the contractor The importance of good documentation cannot

be overemphasized

An old adage says, ‘‘A picture is worth a thousand words.’’ In con-struction, drawings are the picture, and specifications are the thou-sand words But for projects of importance or great value where the work is accomplished by contract between owner and builder, it is important that there be good specifications in addition to the drawings

to define the relationships between the parties The purpose of this chapter is to review the nature of contracts and then to define drawing preparation and specification organization and writing well enough that the reader will have an understanding of and be prepared to practice the basic techniques of document preparation

Since drawings and specifications become a part of a construction contract, they become legal documents As such, they must define the work to be done clearly, completely, and unambiguously Although this ideal is seldom achieved, designers must do their best to meet these criteria Lawsuits involving millions of dollars have been filed based

on the interpretation of a few sentences in the specifications or a lack

of clear detail on the drawings

At the same time as contract documents are identified as being of paramount importance to the relationship between owner and

con-tractor, remember that document preparation has a cost which must

be reasonable and a schedule which must be met No project has an infinite amount of time or resources which can be allocated to the design effort The result is that documents should be adequate, but not overdone, should be prepared deftly and in an organized fashion, all arranged to fully reflect the owner’s hopes and the designer’s in-tent

13.2 The Nature of Contracts

In the United States, the law allows two or more individuals or com-panies or institutions to contract with each other for an exchange of

goods or services In HVAC work, a building owner, called the owner, will typically arrange with a vendor or installer, called the contractor,

to furnish and install equipment and related material in a system Often the HVAC work is performed in conjunction with the full com-plement of building construction The agreement between the owner and the contractor contains the basic elements of any legal contract;

i.e., there is a work or service of value committed to deliver, there is

compensation for the work performed, and there is a time period of

performance All three components are required to establish a valid contract

Most construction is undertaken by contract, where the specifica-tions and drawings define the work to be done and the contract in-cludes a description of compensations and a date of completion There are often penalties for failure to perform in a timely manner and some-times bonuses for early completion

Persons signing the contract must be authorized to do so This is self-evident in the case of a private individual, a proprietorship, or a partnership In the case of a corporation, the board of directors must have given authority to the signator for his or her signature to be valid and binding on the company Signatures are often witnessed or nota-rized

13.3 Drawings

As already noted, contract drawings are legal documents and thus should avoid ambiguity This consideration leads to several criteria which are typical of good drawings

The efforts take design time The alternative—providing inadequate information, neglecting details, and careless checking—can take a great deal more time later on, can cost money for extras, and even can lose the confidence of the client in the designer’s competence

13.3.1 Drawing size and scale

Drawing size and scale should be appropriate for the work being de-scribed Typical drawing sheet sizes are described both by letter and

by sheet dimension

Size Dimension

A 8 1 ⁄ 2 ⫻ 11

D 24 ⫻ 36 (22 ⫻ 34)

Special sizes may be custom-ordered Smaller sheets can be included

in a book of specifications Larger sheets are almost always presented

as a set, except in the case of only one or two sheets, where they may

be neatly folded and placed in pockets in the specification book The drawing scale is determined by the amount of detail to be pre-sented for the dominant aspects of the work For building construction,

1⁄8in⫽ 1 ft is a common scale A very large building may have a plan view at 1⁄16 in ⫽ 1 ft for an overview and routing of major systems, with sectionalized drawings at larger scale Note that doubling a scale uses 4 times the drawing area to make the presentation

A common plan dimension for commercial and institutional con-struction is 1⁄8 in ⫽ 1 ft For residential floor plans and for layouts needing more detail and near-dimensional accuracy than can be ex-pected of 1⁄8- and 1⁄16-in scales,1⁄4in⫽ 1 ft is used Many mechanical room layouts are presented at 1⁄4-in scale When much detailed pre-sentation is needed, larger scales such as 1⁄2 in ⫽ 1 ft, 3⁄4 in ⫽ 1 ft,

1 in⫽ 1 ft, 11⁄2in⫽ 1 ft, and 3 in ⫽ 1 ft are employed For no apparent reason, many civil engineers involved in construction use 3⁄32-, 3⁄16-, and 3⁄8-in scales No matter which scale is chosen, it is helpful and important for all members of the design team to use common scale(s) This helps to avoid errors and makes the overall drawing set easier

to read and interpret

13.3.2 Drawing character

Line work, whether hand-drawn or computer- or plotter-generated, should be clear, sharp, and accurate Lettering should be neat, uni-form, and legible The appearance of the drawings can go far to es-tablish the credibility—the acceptance or the lack of acceptance—of the product, which is the design Early in the development of

aided design (CAD) techniques, it was felt that

computer-generated drawings lacked the ‘‘character’’ of well-presented hand-drawn work But over time, with improved software and increased CAD drafter skills, computer-generated drawings can have all the character of hand-drawn work plus a greater degree of consistency and accuracy

13.3.3 Adequate information

Enough views, both plan and section, should be drawn to fully present

the work Details should be numerous and explicit Standard details

are often useful and save time, as long as the application is really standard Failure to tailor standards to actual conditions can be an embarrassing, even costly experience

13.3.4 Drawing legends

Symbols and abbreviations should be defined in a legend There are many regional or office-specific legends, but no universally accepted industry standards, although ASHRAE, among others, has suggested

a set of symbols in the ASHRAE Handbook Fundamentals.1 Several government agencies have standards of their own which they require

to be used on their projects

13.3.5 Diagrammatic drawings

Schematic diagrams for system flow and control are very helpful to both the installer and the user A complete and detailed schematic will answer most questions about concept and performance Such diagrams

are sometimes referred to as flow diagrams, isometrics, or P&I (pro-cess and instrumentation) diagrams.

13.3.6 Schedules

Equipment schedules with tabular equipment performance informa-tion should be on the drawings rather than in the specificainforma-tions Ex-perience shows that the installer often doesn’t have (or doesn’t refer to) the specifications After the job is completed, the drawings are al-most always available while specifications have a way of disappearing Equipment schedules then become a valuable resource for the owner Some design offices include full equipment specifications on the draw-ings, but this seems to take more document preparation time and may make it more difficult to coordinate drawings and specifications if changes are needed

13.3.7 Minimize sources of information

A good rule for presentation of quantitative information is to show it only once on the drawings and not to call out information on the draw-ings that is covered in the specifications, or vice versa This reduces the potential for error as well as the amount of information which must be updated when changes are made

13.3.8 Quality control—checking

Drawings should be carefully checked for errors and omissions, pref-erably by the system designer Some offices use an independent checker to take a fresh look at the near-final product

13.3.9 Use of computers in drafting

The use of computers in design, drafting, and specification writing has proliferated in recent years.2 Computer-aided design and drafting

(CADD) systems are available for lease or purchase or on a timeshar-ing basis from computer service companies As software has become more sophisticated, the systems have become easier to use However,

to use these systems requires a considerable investment in equipment and in training of personnel A CADD system, properly designed and used, will almost always save time and money eventually, but time and costs may increase initially during the learning period Many gov-ernment agencies and private institutions are so committed to CADD that such capability is a requirement to obtain work

13.4 Specifications

Most of the construction industry now uses a format developed by the Construction Specifications Institute (CSI) for specifications.3 This is

a standardized outline of contract and construction material with forms for the contract work and with section and subsection numbers for each technical topic The system includes flexibility for adding in-formation unique to a project For details, contact the Construction Specifications Institute, 601 Madison St., Alexandria, Virginia 22314 See Fig 13.1

13.4.1 Contractual matters, or boilerplate

Preceding the technical specifications, which with the drawings define the actual work to be accomplished, there is usually additional docu-mentation which establishes the contractual relationship between the

Figure 13.1 Masterformat.

Figure 13.1 (Continued )

contractor and the owner Such documentation may include the follow-ing:

Invitation to bid (instruction to bidders): A section which describes the nature of the project, establishes the time and place for sub-mitting bids, and expresses any other qualification or action re-quired of potential bidders

Bid forms: A formal document for the contractor to fill out to pro-pose a price for completing the work described by the contract doc-uments The proposal may call for a lump-sum price or may be writ-ten on a unit-price, hourly cost (time and materials), or cost-plus-fee basis

Sometimes there is a base bid with additive or deductive

alter-nates The alternates give the owner a chance to adjust the cost of

the project to meet available funding

Bonds: Insurance policies Since contractors sometimes fail to

com-plete the work as contracted, some projects require a payment bond

which guarantees to the owner that the contract will be completed, even by a third party if necessary

General conditions: Often a lengthy document spelling out in great detail the behaviors required of the owner and the contractor in the conduct of the work Standard industry forms of this document are often used [see the American Institute of Architects (AIA) form

A-201 or Engineering Joint Documents Council (EJDC) form 1910-8]

The general conditions may be modified with job specific

supple-mental general conditions.

In preparing elements of the contractual papers or boilerplate, it is helpful to use standard document forms which have a common origin and have been checked for legal consistency between the different forms Such are available from the AIA and EJDC Other entities such

as federal and state institutions as well as corporations may have their own forms and formats In this litigious U.S society, it is imperative that these documents be clear and consistent

13.4.2 Technical specifications

Following the information which describes the legal characteristics of the contract between the contractor (vendor and installer), the tech-nical specifications describe in more or less detail which materials are

to be used and how they are to be installed The drawings, usually at reduced scale, indicate the form of the installation Drawings and

specifications complement each other Drawings usually identify

quan-tity, specifications cover quality.

There is no legally prescribed format for technical specifications Any presentation of information which gets the contractor to do what the owner wants in a timely and cost effective manner can be consid-ered a good specification Decades ago, virtually every office had its own arrangement for specifications Different components of construc-tion could be found in almost any order, and the verbal expression could take almost any format Roughly since World War II, there has been a gradual but discernible trend toward what is now a highly sophisticated and almost universally accepted arrangement for pre-senting technical specification information The general format can probably be attributed to the federal government in its several agen-cies which oversee construction of thousands of projects

As background for specification organization, recognize that many different trades may work on a single project, but for clarity and ease

of bidding and quality control, it is helpful to group work for a given trade in one area or section of the specification At the same time, recognize that a single contract between the owner and contractor for many elements of work creates a commitment for the contractor for all work, whether it is well arranged or not; but it may be difficult for the contractor to apportion work between trades, between subcontrac-tors, if the specification is fragmented

The format which has gained general construction industry accep-tance has 16 divisions for major categories of work These divisions are listed in Fig 13.2 Each division is broken down into sections with

as many sections and as much depth as needed to convey the criteria for the work (see Fig 13.3)

Each section in turn has a format containing three parts, as indi-cated in Fig 13.4

As stated before, specifications can be written with more or less detail as desired Specifications for residential housing are often ab-breviated to 3 to 5 letter-size pages for the whole house, relying on the habit of the contractor for most detail In contrast, specifications for large buildings contracted for through competitive bidding, which requires tight quality control, may be several hundred pages long Where many small items and work descriptions are involved, they may be lumped together in a single section A major component which requires much detail to describe, such as a chiller or a boiler, may be given its own section

The organization of specifications as described above leads to a file full of specifications for every imaginable product and construction

method To the extent that the writings are generic, they become

mas-ter specifications and can be referenced over and over from one project

䡲 Bidding requirements, contract forms, conditions of the contract

䡲 Technical specifications

01000 General requirements

02000 Site work

03000 Concrete

04000 Masonry

05000 Metals

06000 Wood and plastics

07000 Thermal and moisture protection

08000 Doors and windows

09000 Finishes

10000 Specialties

11000 Equipment

12000 Furnishings

13000 Special construction

14000 Conveying systems

15000 Mechanical

16000 Electrical

Note: Other divisions are sometimes added in specialized construction such as for

industrial plants Not all divisions may be required for every project.

Figure 13.2 Technical specification format with 16 divisions.

to another in the design office Such a file saves time and encourages consistency among the design staff

There are pitfalls, however Specification information becomes out-dated and inaccurate as products and methods change More chal-lenging are the nuances between one job and the next which require careful editing of previous or master text to avoid major errors and costly mistakes Keeping a master specification up to date requires a major commitment of time

13.4.3 Specification language

While allowing every specification writer the latitude to be an indi-vidual in the drafting of specifications, there are a few suggestions which can be helpful to all:

1 Use good English, good grammar, and a good vocabulary Don’t use slang or colloquialisms (jargon)

2 Use as few words as possible without losing the meaning

3 Use a direct rather than indirect form of expression Do it! is more effective than The contractor shall do it.

Many specifications have been written that use shall as the

im-perative This is now seen as an awkward way of giving direction

4 As with report writing, keep the sentence structure simple and clear Avoid overly complex or long sentences and phrases