--``,`,```,`,,`,`,,````````,,,``-`-`,,`,,`,`,,`---ISO 13789, Thermal performance of buildings — Transmission and ventilation heat transfer coefficients — Calculation methodISO 13790, Ene
Energy uses
The assessment of the annual energy used by a building shall comprise the following services:
— lighting (optional for residential buildings);
The annual energy use includes auxiliary energy and losses of all systems.
National authorities determine whether the energy used for lighting in residential buildings, along with energy for transportation, electrical appliances, cooking, and industrial processes across various building types, should be factored into the calculated energy rating.
NOTE Energy uses for lighting and other services are included in the measured energy rating.
Assessment boundaries
The system boundary, which must be clearly defined prior to the energy performance assessment, pertains to the rated object, such as a flat or building.
Inside the system boundary, the system losses are taken into account explicitly; outside the system boundary, they are taken into account in the conversion factor.
Energy can flow across the system boundary through imports and exports This flow can be measured using meters for various energy carriers, including gas, electricity, district heating, and water The defined system boundary for these energy carriers includes the meters for gas, electricity, district heating, and water, as well as the loading port of storage facilities for liquid and solid energy carriers.
If a component of a technical building system, such as a boiler, chiller, or cooling tower, is situated outside the building envelope but is included in the assessed building services, it is regarded as being within the system boundary Consequently, the system losses associated with this component are explicitly considered.
Figure 2 — Boundary — Examples of energy flows across the system boundary
The following two figures illustrate the energy flows inside and across the system boundary.
NOTE 1 These illustrations are more complete than Figure 2.
Recoverable heat or cold from systems can be utilized within the building, leading to a reduction or increase in the energy requirements for heating and cooling.
Figure 3 — Boundary and energy flows — Main energy flows within and crossing the boundaries
Figure 4 — Boundary and energy flows — More detailed view on the energy flows for produced, used, and exported electricity at and from the building site
The energy contributions from collectors to the building are included in the overall energy balance, with decisions regarding their classification as part of the delivered energy made at the national level.
The assessment can be made for a group of buildings if they are on the same lot or are serviced by the same technical systems.
Specific rules for the boundaries, depending on the purpose of the energy performance assessment and the type of the buildings, may be provided at national level.
Types and uses of ratings
This Internatonal Standard gives two principal options for energy rating of buildings:
The calculated energy rating encompasses energy consumption for heating, cooling, ventilation, hot water, and, when applicable, fixed built-in lighting It excludes energy for other services unless specified at the national level Consequently, comparing both ratings requires special caution, as outlined in Clause 8.
The design rating, determined by national standards, incorporates conventional climate, usage, environmental factors, and occupant-related data specified in a national annex for planned buildings.
— tailored, calculated with climate, occupancy, and surroundings data adapted to the actual building and the purpose of the calculation.
The assessment method of the measured energy rating is given in Clause 8.
— which type of rating applies for each building type and purpose of the energy performance assessment,
— under what conditions the design rating can be considered as or converted to a calculated energy rating for the actually realized building, and
— if renewable energy produced on site is part or not of delivered energy.
The types of rating are summarized in Table 1.
Name Input data Utility or purpose
Calculated Design Standard Standard Design Building permit, certificate under conditions
Standard Standard Standard Actual Energy performance certificate, regulation Tailored Depending on purpose Actual Optimization, validation, retrofit planning Measured Operational Actual Actual Actual Energy performance certificate, regulation
Types of ratings and indicators used
NOTE 1 Annex G contains a worked example of the procedures in this clause.
ISO 16343 outlines various levels of energy performance ratings, ranging from integrated building energy performance to component-level assessments It is worth considering whether the performance ratings for building envelopes and systems would be more appropriately included in ISO 16343.
ISO/FDIS 23045 presents a list of indicators for the different aspects of the energy efficiency of buildings, as in the following:
— performance of the building envelope;
— performance of the building envelope including the building technical systems;
— performance of technical building systems;
— performance of the building expressed in terms of primary energy use;
— performance of the building expressed in terms of related CO2.
Indicators can be presented as absolute values reflecting the overall performance of a building or as relative values for comparing similar buildings or technical systems Since the energy required and delivered is closely linked to the intended comfort levels, it is essential to define indoor design conditions during the project planning phase.
The efficiency and performance factors are determined based on the heated and/or cooled area as specified in ISO 16818 In cases where this is not applicable, the floor area definition should be used, as most factors can be correlated to this area.
Buildings typically utilize multiple energy carriers, necessitating a unified expression to aggregate their consumption This aggregation often involves different units and reflects varying impacts on energy efficiency and sustainability.
According to this International Standard, the aggregation methods are based on the following impacts the use of energy have:
— parameters defined by national energy policy.
NOTE 3 Cost is a parameter that may be used in the energy policy aggregation method.
Types of factors or coefficients
The aggregation requires specific factors and coefficients established at the national level, as outlined by the following regulations It is essential to define the values for these factors in a national annex to accurately calculate primary energy consumption and CO₂ emissions.
NOTE 6.4.2 provides factors which can be used if no national values are given.
In a multi-plant generation system, such as electricity or district heating, the weighting factor varies based on the continuous operation of generation plants and the impact of changes in energy demand It is essential to differentiate between average, marginal, and end-use factors for effective aggregation.
Changes in energy consumption or production impact power stations differently, with "base load" stations maintaining consistent operations When demand decreases, other plants adjust their output accordingly Additionally, energy exported by a building can lessen the necessity for constructing new power plants.
The marginal factor or coefficient focuses solely on production units influenced by changes in energy demand or production For instance, the marginal new plant factor pertains to a new facility that may need to be constructed in response to rising energy demand or the electricity saved through exports generated at existing sites.
6.2.4 End-use factor or coefficient
Various services such as lighting, heating, and air-conditioning exhibit distinct demand patterns at different times These unique demand profiles may warrant the application of specific demand-weighted factors tailored to each end use.
The environmental declaration, as defined in ISO 14025, is based on the Life Cycle Assessment (LCA)
Methodology Information about use of energy resource and CO 2 can be used as a basis to express the useful indicator related to primary energy or CO 2
Energy use indicator
The energy use indicator reflects the effectiveness of a building's envelope, independent of the performance of its technical systems This metric highlights the building's inherent capacity, acknowledging that its lifespan may surpass that of its technical components.
This indicator is calculated from the energy use for heating, cooling, and lighting including solar and internal gains but no heat recovery by technical systems.
Q i is the energy needed for any purpose, as defined in 5.1.
NOTE Recovered losses are not taken into account as they are related to the definition of the technical building systems.
This indicator can be utilized as an absolute value, measured in megajoules (MJ) or kilowatt-hours (kWh), or as a relative value in relation to the energy consumption per unit area of the building.
Primary energy rating
The primary energy approach makes possible the simple addition from different types of energies (e.g thermal and electrical) because primary energy includes the losses of the whole energy chain, including
``,`,```,`,,`,`,,````````,,,``-`-`,,`,,`,`,,` - those located outside the building system boundary These losses (and possible gains) are included in a primary energy factor.
When building A supplies heat to building B, which lies beyond the assessment boundaries, this heat is treated similarly to district heating The primary energy factor for building B accounts for system losses, including generation and heat losses during transfer from building A to building B.
Primary energy factors differ globally; however, a standardized "ISO" energy performance indicator can facilitate international comparisons of building energy performance For this purpose, the data presented in Table 2 should be utilized.
International comparisons in building design can be misleading due to varying primary energy factors, climate conditions, and operational assumptions Therefore, it is essential to tailor building designs to specific local conditions rather than relying on average international values.
The ISO weighted energy use, E ISO , is calculated from the delivered and exported energy for each energy carrier:
ISO=∑ ISO;del; −∑ ISO;exp;
E ISO;del; ci =E EPdel,c i ×f ISO,del,c i
E ISO;exp; ci =E exp,c i ×f ISO,exp,c i
E ISO is the annual ISO weighted energy use for all energy uses included in the energy perfor- mance assessment, in MJ or kWh;
E ISO;del; ci is the annual delivered energy in ISO weighted energy units, for energy carrier ci, in MJ or kWh, determined according to Formula (3);
E ISO;exp;ci is the annual exported energy in ISO weighted energy units, for energy carrier ci, in MJ or kWh, determined according to Formula (4);
E EPdel; ci is the annual delivered energy, for energy carrier ci, for all energy uses included in the energy performance assessment, in MJ or kWh, determined according to Formula (10);
The annual exported energy for energy carrier \(c_i\), measured in MJ or kWh, is represented by \(E_{exp;ci}\) and is calculated using Formula (17) for electricity and Formula (18) for thermal energy The ISO factor for the delivered energy carrier \(c_i\), denoted as \(f_{ISO,del,ci}\), is determined based on the information provided in the corresponding table.
2; f ISO,exp, ci is the ISO factor for the exported energy carrier ci, to be determined according to
Table 2 — Conversion factors for ISO weighted energy use f ISO,del,ci and f ISO,exp,ci
Total energy factor Non-renewable energy factor
NOTE 2 For Table 2, the results of an inventory of national primary energy conversion factors have been used.
The annual primary energy use, E P , is calculated from the delivered and exported energy for each energy carrier:
E P is the annual primary energy use for all energy uses included in the energy performance assessment, in MJ or kWh;
E P;del;ci is the annual delivered energy in primary energy units, for energy carrier ci, in MJ or kWh, determined according to Formula (6);
E P;exp; ci is the annual exported energy in primary energy units, for energy carrier ci, in MJ or kWh, determined according to Formula (7);
E EPdel;ci is the annual delivered energy, for energy carrier ci, for all energy uses included in the energy performance assessment, in MJ or kWh, determined according to Formula (10);
The annual exported energy, denoted as \$E_{exp,ci}\$, is measured in MJ or kWh and is calculated using specific formulas for electricity and thermal energy The primary energy factor for the delivered energy carrier, represented as \$f_{P,del,ci}\$, is determined according to section 6.2 Similarly, the primary energy factor for the exported energy carrier, denoted as \$f_{P,exp,ci}\$, is also established in accordance with section 6.2.
These two factors, f P,del, ci and f P,exp, ci , can be the same.
Table 2 is used for the primary energy calculations The energy used for different purposes and by different fuels is recorded separately.
There are two main conventions for defining primary energy factors: the total primary energy factor and the non-renewable primary energy factor The total primary energy factor accounts for all energy overheads involved in delivering energy to the point of use, including production, transport, and extraction, resulting in a factor that always exceeds one In contrast, the non-renewable primary energy factor considers only the energy overheads while excluding renewable energy components, which can result in a factor less than one for renewable sources It is essential that primary energy factors encompass these considerations.
— energy to extract the primary energy carrier,
— energy to transport the energy carrier from the production site to the utilization site, and
— energy used for processing, storage, generation, transmission, distribution, and any other operations necessary for delivery to the building in which the delivered energy is used.
The primary energy factors may also include
— energy to build the transformation units,
— energy to build the transportation system, and
— energy to clean up or dispose the wastes.
National annexes may include tables that represent local conditions for electricity generation and fuel supply, as outlined in this International Standard These tables will provide values for primary energy factors or non-renewable primary energy factors, based on national requirements Examples of these factors can be found in Annex B.
National annexes defining primary energy factors and non-renewable primary energy factors must specify the included overheads, such as energy for building transformation and transportation systems When fuel coefficients are provided by energy unit, they should be based on gross calorific values Additionally, the national annex must clearly indicate the type of factor or coefficient used as defined in section 6.2.
Carbon dioxide rating
The emitted mass of CO 2 is calculated from the delivered and exported energy for each energy carrier: m CO 2 =∑ ( E del,c i ×k del ci , )−∑ ( E exp,c i ×k exp, ci )
E del,ci is the delivered energy for energy carrier ci, according to 7.2;
The exported energy for energy carrier \( c_i \) is denoted as \( E_{\text{exp}, c_i} \), as outlined in section 7.2 The CO\(_2\) emission coefficient for the delivered energy carrier \( c_i \), represented as \( k_{\text{del}, c_i} \), is to be determined according to section 6.2 Similarly, the CO\(_2\) emission coefficient for the exported energy carrier \( c_i \), denoted as \( k_{\text{exp}, c_i} \), will also be established in accordance with section 6.2.
The two coefficients K del,ci and K exp,ci can be the same.
The CO2 emission calculation shall be reported in accordance with Table 3.
Table 3 — Calculation of ratings (example: CO 2 rating)
1 Energy delivered (unweighted) E del,1 E del, i
2 Weighting factor or coefficient k del,1 k del,i
3 Weighted delivered energy or CO 2 m CO 2 , del 1 , m CO 2 , del , i ồ m CO 2 , del , i
4 Energy exported (unweighted) Q exp,T E exp,el
5 Weighting factor k exp,T k exp,el
6 Weighted exported energy or CO 2 m CO 2 , exp T , m CO 2 , exp el , m CO i
The CO2 emission coefficients must encompass all carbon dioxide emissions linked to the primary energy utilized by the building, as outlined in section 6.4 It is essential to establish at the national level whether these coefficients will also account for the equivalent emissions of other greenhouse gases, such as methane.
Any national annex specifying CO₂ emission coefficients must clarify which additional overheads from section 6.2 are included When fuel coefficients are expressed per energy unit, they should be based on gross calorific values Additionally, the annex must indicate the type of coefficient utilized as defined in section 6.2.
Policy energy rating
To shape citizens' energy behavior, policymakers can implement measures that either promote or penalize specific energy carriers The energy policy rating is determined by assessing the energy delivered and exported for each type of energy carrier.
E pol =∑ ( E del,c i ×f pol,del,c i ) − ∑ ( E exp,c i × f pol,exp,c i ) (9) where
E del,ci is the delivered energy for energy carrier ci, according to 7.2;
The exported energy for energy carrier \( c_i \) is represented by \( E_{\text{exp},c_i} \), as outlined in section 7.2 The policy factor for the delivered energy carrier \( c_i \), denoted as \( f_{\text{pol,del},c_i} \), will be determined according to section 6.2 Additionally, the policy factor for exported energy, \( f_{\text{pol,exp},c_i} \), is also to be established in accordance with section 6.2.
Calculation procedure
The calculation direction goes from the needs to the source (e.g from the building energy needs to the primary energy).
Electrical services (e.g lighting, ventilation, auxiliary) and thermal services (e.g heating, cooling, humidification, dehumidification, domestic hot water) are considered separately inside the building boundaries.
The building’s on-site energy production based on locally available renewable resources and the delivered energy are considered separately.
NOTE Annex B provides some information on the methods for collecting building data in the case of existing buildings.
The calculation aims to assess the annual total energy consumption, primary energy usage, or CO₂ emissions This evaluation can be conducted through one of two distinct methods for various energy services.
— Calculation is performed using annual average values.
Calculation involves dividing the year into various steps, such as months or hours, and executing calculations for each step using values specific to that step The final results are obtained by summing the outcomes of all steps throughout the year.
NOTE The use of annual values is unsatisfactory in many cases, especially when calculating CO 2 emissions of seasonal energy uses.
Reporting tables summarize the annual energy performance of the building envelope and the technical building systems The time step in these tables is the year.
7.1.3 Calculation principles of the recovered gains and losses
The calculation of heat gains and recoverable system losses considers the interactions among various energy services, such as heating, cooling, and lighting, which can significantly influence the building's energy performance, either positively or negatively.
Calculations begin with the building's requirements as outlined in ISO 13790 Heat gains and recoverable thermal losses, such as solar and metabolic heat gains, must be defined at the national level The report should clearly specify which heat gains and recoverable thermal losses have been considered.
There are two methods for considering recoverable thermal losses that are not initially included in the building's energy requirements, as outlined in section 7.1.3.2 and the relevant definitions in ISO/TR 16344 It is important to note that the chosen method may vary depending on the specific technical building systems involved.
In a holistic approach, the calculation of thermal energy needs takes into account the combined effects of heat sinks and sources within the building, as well as the recoverable energy from technical building systems for space conditioning.
As the technical building thermal systems losses depend on the energy input, which itself depends on the recovered system thermal sources, iteration might be required.
The calculation procedure involves several key steps: First, perform subsystem calculations in accordance with EN 15241, EN 15243, and EN 15316, or relevant International Standards to determine recoverable thermal system losses Next, incorporate these losses with other recoverable heat sources, such as solar gains and internal heat from lighting, into the heating and cooling needs assessment Subsequently, recalculate the thermal energy requirements for heating and cooling This process should be repeated until the energy needs between iterations differ by less than a specified limit (e.g., 1%) or until a predetermined number of iterations is reached, as defined by national guidelines Finally, calculate the difference in energy from the beginning to the end of the iterations to identify the recovered system thermal losses.
In the simplified method, the system's heat losses are calculated by multiplying the recoverable thermal losses by a standard recovery factor, which are then directly deducted from the losses of each technical building system evaluated.
The calculation procedure involves several key steps: first, perform the subsystem calculation in accordance with EN 15241, EN 15243, and EN 15316 series, or other relevant standards specified in Annex A to determine the recoverable system thermal losses Next, calculate the recovered thermal system losses by applying a conventional recovery factor to the recoverable thermal losses Finally, subtract the recovered thermal system losses from the total thermal system losses to obtain the final results.
The recovered thermal system losses have to be included per energy carrier before the final energy rating The procedure is given in 7.4.2.
Conventional recovery factor values are typically provided at the national level In the absence of a national value, the recovery factor is determined to be 80% of the utilization factor derived from the heat balance gains, as calculated using the monthly method in accordance with ISO 13790.
For complex systems (e.g heating and cooling installations), the holistic approach is recommended.
NOTE 1 Heat recovery in systems (e.g preheating of the combustion air or recovery from exhaust air) is treated in applicable system standards.
The preferred option is to take the effects of control systems into account directly when calculating the energy delivered and not as a factor at the end of the calculation.
As a simplified approach, the impact of integrated controls combining the control of several systems may be taken into account according to EN 15232 or the relevant standards listed in Annex A.
Set of formulae
The annual delivered energy for energy carrier ci, E del,ci , is equal to Formula (10) or Formula (11). For electricity (ci = el):
The annual delivered electricity, denoted as \$E_{\text{del;el}}\$ , is calculated by subtracting the electricity generated on-site—such as from combined heat and power (CHP), photovoltaic (PV) systems, and wind power—from the total electricity consumed for energy performance.
E EPdel;el =E EPus,el −E pr,EPus,el
For all other energy carriers:
The annual delivered energy for energy carrier ci, E del,ci , is equal to the energy, in the form of this energy carrier, that is used for the energy performance:
It is currently assumed that thermal energy generated on-site, such as from thermal solar energy systems, is always included in the evaluation of the system's energy consumption.
The annual delivered energy for energy carrier \( c_i \), denoted as \( E_{Pdel} \), encompasses the total energy performance, including any energy utilized for on-site energy production, measured in megajoules (MJ) or kilowatt-hours (kWh).
Energy utilized for on-site production, such as gas or coal in a local Combined Heat and Power (CHP) system, is crucial The advantages of electricity generation are reflected in the terms E pr;EP;us,ci and E exp; ci, specifically in Formulae (10) and (11) for production, and Formulae (1) to (7) for expenditure, where ci represents electricity.
E EPus;ci is the annual used energy for the energy performance, for energy carrier ci, in MJ or kWh, determined according to Formulae (12) and (13);
E pr;EPus;el represents the annual electricity generated on-site that is utilized for energy performance at the building site, measured in MJ or kWh, as defined by Formula (14).
The phrase "that is used at the building site for the energy performance" is essential, as it clarifies that there may be additional electricity uses at the site, such as specific appliances, which are not accounted for in the energy performance assessment but still consume a portion of the generated electricity.
The annual used energy for the energy performance, for energy carrier ci, E EP;us;ci , is equal to Formula
E EPus,el = E H,el + W H;aux + E hum,el + W hum;aux + E V;el + E L;el + E C,el + W C C;aux + E dhum,el + W dhum;aux + E W,el + W W;aux
For all other energy carriers:
E EPus, ci =E H, i c +E hum, ci +E V, ci +E L, ci +E C, ci +E dhum, ci +E W, ci
Auxiliary energy is commonly defined as electric energy, primarily associated with lighting and ventilation systems like fans However, it is important to note that this definition is not restrictive, as these systems can also utilize other energy carriers.
E EPus;ci is the annual used energy for the energy performance, for energy carrier ci, in MJ or kWh;
The annual energy consumption for space heating, denoted as E H, ci, is measured in megajoules (MJ) or kilowatt-hours (kWh) This measurement is based on the specific energy carrier ci and is determined in accordance with the applicable standards for heating systems outlined in Annex A.
W H;aux is the annual energy used for auxiliary energy for space heating, determined according to the relevant standard for space heating systems, listed in Annex A;
E hum,ci represents the annual energy consumption for humidification, measured in megajoules (MJ) or kilowatt-hours (kWh) This value is calculated based on the applicable standards for humidification systems, as outlined in Annex A.
W hum;aux is the annual energy used for auxiliary energy for humidification, determined accord- ing to the relevant standard for humidification systems, listed in Annex A;
The annual energy consumption for ventilation, denoted as E V,ci, is measured in megajoules (MJ) or kilowatt-hours (kWh) This value is calculated based on the applicable standards for ventilation systems, as outlined in Annex A.
The annual energy consumption for lighting, denoted as E L,ci, is measured in megajoules (MJ) or kilowatt-hours (kWh) This measurement is based on the applicable standards for lighting systems, as outlined in Annex A.
The annual energy consumption for space cooling, denoted as E C,ci, is measured in megajoules (MJ) or kilowatt-hours (kWh) This value is calculated based on the applicable standards for cooling systems, as outlined in Annex A.
W dhum;aux is the annual energy used for auxiliary energy for dehumidification, determined according to the relevant standard for dehumidification systems, listed in Annex A;
E W,ci represents the annual energy consumption for heating domestic hot water, measured in either MJ or kWh This value is determined based on the applicable standards for domestic hot water heating systems, as outlined in Annex A.
W W;aux represents the annual energy consumption for auxiliary heating of domestic hot water, as defined by the applicable standards for domestic hot water heating systems outlined in Annex A.
In these formulas, the energy consumption is categorized by type of energy use (such as heating and work) If a single generator serves multiple energy purposes, the total energy used must be allocated among the various applications.
Building thermal needs
Table 4 presents the thermal requirements, thermal transfers, heat gains, and recoverable thermal losses of the building, with its rows and columns tailored to the specific building in question.
Heating Cooling Domes- tic hot water Sensible heat Latent heat
Sensible heat Latent heat (dehu- midification)
L1 Building heat gains and recov- erable thermal losses a Q H,gna
L2 Building thermal transfers Q H,ht — Q C,ht — —
L3 Building thermal needs Q H,nd Q H,hum,nd Q C,nd Q C,dhum,nd Q W,nd a If applicable.
The necessary inputs are calculated according to the International Standards listed below.
Q H,nd energy need for space heating (without humidification) ISO 13790
Q C,nd energy need for space cooling (without dehumidification) ISO 13790
Q W,nd energy need for domestic hot water EN 15136-3-1/See Annex A
Q H,ht heat transfer by transmission and ventilation of the building when heated ISO 13790
Q C,ht heat transfer by transmission and ventilation of the building when cooled ISO 13790
Q H ,gn internal and solar heat gains of the building when heated ISO 13790
Q C , gn, internal and solar heat gains of the building when cooled ISO 13790
Q H ,ls,rbl recoverable thermal losses of technical building systems when heated ISO 13790
Q C,ls,rbl , recoverable thermal losses of technical building systems when cooled ISO 13790
Q H,hum,nd thermal energy for humidification EN 15241/See Annex A
Q C,dhum,nd thermal energy for dehumidification EN 15243/See Annex A
Technical building systems
7.4.1 Technical system thermal losses, electrical and auxiliary energy without building genera- tion devices
The system losses and the electrical and auxiliary energy without generation are reported using Table 5.
Table 5 — System thermal losses and auxiliary energy without generation
Heating Cooling Domestic hot water Ventilation Lighting
L4 Electrical energy W H,ngen W C,ngen W W,ngen E V E L
L5 System thermal losses Q H,ngen,ls Q C,ngen,ls Q W,ngen,ls
L6 Recoverable system ther- mal losses Q H,ngen,ls,rbl Q C,ngen,ls,rbl Q W,ngen,ls,rbl Q V,ls,rbl Q L,ls,rbla
L7 Thermal input to distribu- tion system Q H,dis,in Q C,dis,in Q W,dis,in a Q L,ls,rbl is the recoverable heat dissipated by the lighting system.
NOTE The values in this table are the presentation of the results of other International Standards It is not possible to calculate missing values by arithmetic in this table.
The system thermal losses without the building generation devices include the emission, distribution, and storage losses (if not included in the generation part) of the respective system.
The thermal output of the cooling distribution system includes the thermal need for dehumidification. The thermal output of the ventilation system includes the thermal need for humidification.
The necessary inputs are calculated according to the International Standards listed below.
W H,ngen thermal losses, auxiliary energy of the heating systems without generation EN 15316-1/
W C,ngen thermal losses, auxiliary energy of the cooling system without generation (including dehumidification) EN 15243/15241/
W W thermal losses, auxiliary energy of domestic hot water system without generation EN 15316-3-2/
Q V,ls,rbl energy use for ventilation (including humidification) and system thermal losses EN 15241/
Q L,ls,rbl energy use for lighting and heat dissipated by the lighting system EN 15193/
The thermal energy required for distribution systems must come from either the building's heat generation systems or external sources, such as district heating This heat input is allocated to various building generation devices based on the design of the system, along with any energy supplied directly from outside the building.
Table 6 presents a comprehensive overview of various generation systems, such as cogeneration, heat pumps, refrigeration units, thermal solar, and photovoltaic (PV) systems It also includes energy delivered directly to distribution systems, like district heating and electricity, without any energy transformation.
L8 Thermal output Q, gen,out,1 Q, gen,out,2 Q, gen,out,i
L9 Auxiliary energy W gen,1 W gen,2 W gen,i
L10 System (generator) thermal losses Q gen,ls,1 Q gen,ls,2 Q gen,ls,i
L11 Recoverable system thermal losses Q gen,ls,rbl,1 Q gen,ls,rbl,2 Q gen,ls,rbl,i
L12 Energy input E gen,in,1 E gen,in,2 c
L13 Electricity production E el,gen,out,1 E el,gen,out,2 E el,gen,out,i
The energy carrier refers to the type of system supplied, such as heating, cooling, or hot water, and the specific energy source utilized by the generator, including options like oil, gas, or solar heat Notably, for renewable energy generated on-site or from other generators within the system boundary, no energy input is considered.
When a generator supplies input to another generator, such as a cogenerator for an absorption chiller, it is important to differentiate between the thermal output directed to the distribution system and that used for generation The thermal output, thermal losses, and energy input of the secondary generator are provided for informational purposes but are not included in the energy balance of the generation systems.
In the calculation method for combined heat and power, as outlined in EN 15316–4-4 and relevant International Standards, the energy input and all system losses are associated with the thermal output, while the electricity generated is considered an additional benefit through the power bonus method.
In a heat pump system, the energy balance of a building considers the difference between energy input and thermal output, including thermal losses This difference can be accounted for as heat recovery within the system boundary or as renewable energy generated on-site when heat is extracted through the system boundary, such as in a heat pump utilizing earth heat exchange.
A heat pump can efficiently provide heating for spaces and domestic hot water while also extracting heat for cooling purposes The necessary quantities for heat supply and extraction are detailed in row L8 of Table 6.
If a generator provides energy for heating and cooling, then the generator thermal losses and the auxiliary energy are dispatched between these two services according to the thermal outputs.
The losses in the generator system and the consumption of auxiliary energy are determined based on the relevant sections of EN 15316 and the applicable International Standards outlined in Annex A for heating systems.
``,`,```,`,,`,`,,````````,,,``-`-`,,`,,`,`,,` - according to EN 15243 or the relevant International Standards listed in Annex A for cooling systems, and reported in accordance with Table 6.
Q gen,out,i thermal output of the generation device i (thermal input required by the distribution sys- tems fed by this generator);
Q gen,ls, i system thermal losses of the generation device i;
Q gen,ls,rbl,i recoverable system thermal losses of the generation device i;
W gen,i auxiliary energy of the generation device i;
E el,gen,out,i electricity production of the generation device i;
E gen,in, i energy input to the generation device i;
E gen,in,j equal to the heat output and the electricity output plus the system losses minus, in the sim- plified approach, the recovered system thermal losses.
In the simplified approach, the total recovered thermal system losses are subtracted from the overall thermal system losses To proceed with the calculations until the energy rating is determined for each energy carrier, these recovered thermal losses must be allocated among the various generators The calculation of recoverable thermal losses is essential for this process.
Qgen,ls,rvd,i is the recovered thermal system loss of generator i;
QTot,sys,ls,rvd is the total recovered thermal system loss;
Qgen,out,i is the thermal output of generator i.
At this stage, the energy carriers are taken into account (oil, gas, biomass, district heating, heat from solar systems, PV electricity, etc) They are indicated in row L14 of Table 6.
The building generation system requires input from various energy carriers and renewable energy sources generated on-site, which includes the total thermal and electrical output of the energy generation systems, as well as the thermal losses from the generator.
On-site energy production in buildings is categorized based on system design, distinguishing between energy consumed within the building and energy exported The findings are detailed in Table 8.
The thermal technical building system performances to enter in Table 8 are calculated as follows:
HW,ls,nrvd= H,ngen,ls+∑ H,gen,ls, + W,ngen,ls+ W,gen,ls, ii i
C,ls,nrvd= C,ngen,ls+∑ C,gen,ls, − C,ls,rvd
HW= H,ngen+∑ H,gen, + W,ngen,+∑ W,gen,
General requirements
The amounts of all energy carriers delivered to the building and exported by the building shall be measured and reported in a table based on Table 7.
Table 7 — Accounting energy carriers for measured energy rating
(l, kg, m 3 , kWh, MJ or kWh, etc.)
(Quantities) Gross calorific value Energy delivered
(Energy content in kWh or
District heating, Wood Energy carrier (i) Units
(kWh, MJ, etc.) Energy exported
(Energy content in kWh or
Units (kWh, MJ, etc.) Renewable energy produced on site
NOTE The columns in Table 7 should be adapted to the building concerned.
The annual delivered energy represents the total delivery of each energy carrier, as specified in section 8.3 The exported energy is measured using an export meter or its equivalent Both delivered and exported energy amounts are reported in their respective measurement units To calculate the energy content, the quantity of each energy fuel is multiplied by its gross calorific value.
Assessment period
The amounts in Table 7 shall be assessed as closely as possible for the same period.
The time period should be an integer number of years, calculated as the average over the most recent complete years, provided that the building and its usage pattern have remained consistent.
If the assessment period is not an integer number of years, the annual energy use shall be obtained by extrapolation according to 8.2.2.
If the time period is shorter than three years, a correction for weather according to 8.4 shall be performed
During the assessment period, no alterations to the building that could affect its energy performance should have occurred If any changes have taken place, a new assessment period must commence to obtain an updated energy rating.
It is advisable to disregard the energy usage data from the first or second year after a building's construction, as energy consumption tends to be higher during these initial years for various reasons.
— some additional energy is used to dry the building fabric,
— adjustment of control system may not be perfect from the first day of use, and
— there may be some faults that are corrected during the first year.
To minimize errors in fuel measurement, it is advisable to read meters or assess stored fuel quantities during periods of low energy consumption This approach helps ensure more accurate readings by reducing discrepancies associated with incomplete annual measurements.
8.2.2 Extrapolation to an integral number of years
The suitable approach for evaluating energy carriers is determined by their intended use For energy carriers utilized across multiple services or for those that do not fit the extrapolation methods mentioned, an assessment should be conducted over a specified number of years.
An appropriate building model, utilizing input data and calculation methods such as ISO 13790 for heating and cooling, allows for the extrapolation of measurements taken over a limited timeframe By validating the building model in accordance with Clause 9, a calculated energy rating can be derived.
Possible simpler extrapolation methods, applicable under limited conditions only, are given in 8.2.2.2 to 8.2.2.4.
8.2.2.2 Energy carriers used at constant average power
For energy carriers used at constant average power, the extrapolation is linear:
E t t an E per per (29) where t an is the duration of the year; t per is the assessment time period, which shall be much larger than the time averaging period;
E per is the amount of energy carrier used during the assessment time period.
For example, if the daily average power is approximately constant, t shall be several days If the weekly average is constant, the assessment time period shall be several weeks.
8.2.2.3 Energy carriers used for heating or cooling only
Energy carriers for heating or cooling can be extrapolated using either the energy signature method or the simplified calculation outlined in ISO 13790 These methods are particularly applicable for heating in cold climates, where heating plays a crucial role.
The simplified calculation for extrapolation is as follows The amount of energy carrier used either for heating or for cooling for a whole year is
Q E an an,calc per,calc per (30) where
Q an,calc is the calculated heating or cooling energy need for the whole year;
Q per,calc is the calculated heating or cooling energy need for the assessment period;
E per is the amount of energy carrier used for heating or cooling during the assessment time period.
Q an,calc and Q per,calc are determined using a simplified approach in accordance with ISO 13790, which involves averaging the internal temperature and gains throughout the building without zoning, while employing mean input values.
Q H,calc ( )t =(H tr +H ve )( θ int − θ e ) t − η H,gn ( A I sol sol + Q int ) (31)
The calculation of heat transfer, denoted as \( Q_{C,calc}(t) \), is expressed by the formula \( Q_{C,calc}(t) = (A_{I} \cdot sol_{sol} + Q_{int}) - \eta_{C,ls} (H_{tr} + H_{ve})(\theta_{int} - \theta_{e}) t \) In this equation, \( t \) represents the assessment time period, which corresponds to a complete heating or cooling season, used to determine \( Q_{an,calc} \) and the measurement duration for \( Q_{per,calc} \).
The heat transfer coefficients of a building, denoted as \$H_{tr}\$ and \$H_{ve}\$, are determined by transmission and ventilation in accordance with ISO 13789 The average heating and cooling set point temperatures across the building are represented as \$int,H,set\$ and \$int,C,set\$ The mean external temperature, averaged over a specified time period \$t\$, is indicated by \$e\$ Additionally, the gain utilization factor for heating, calculated per ISO 13790, is represented as \$\eta_{H,gn}\$, while the loss utilization factor for cooling is denoted as \$\eta_{C,ls}\$, also calculated according to ISO 13790.
A sol is an effective solar collecting area representative of the whole building, defined for a specific reference orientation (usually: south vertical);
I sol is the solar irradiation during time period t on the area A sol ;
Q int are the internal gains of the whole building during time t; including recoverable techni- cal system thermal losses, if applicable.
8.2.2.4 For energy carriers used at a rate depending on occupancy
For these, the extrapolation method is
O E an an per per (33) where
O an is the occupancy (e.g average number of occupants in the building) during the whole year;
O per is the occupancy during the assessment time period;
E per is the amount of energy carrier used during the assessment time period.
The confidence interval of the result shall be estimated.
If the confidence interval is too large because of a too short assessment period or because the assessment period is not appropriate (e.g swing seasons), the assessment period shall be extended.
Assessing the used amounts of all energy carriers
The amount of all energy carriers shall be assessed as accurately as reasonably practicable from recorded data, energy bills, or measurements.
Energy carriers that are not metered shall be assessed by calculation according to Clause 7.
To effectively compare the measured rating with a customized calculated rating, it is essential to evaluate the energy consumption for services beyond heating, cooling, ventilation, hot water, and lighting This includes energy used for cooking, washing, and production units Such energy use should be assessed separately, utilizing either distinct metering or accurate estimations of power and operating time.
8.3.2 Metered fuels (electricity, gas, district heating, and cooling)
Energy use is the difference of two readings of the meter taken at the beginning and the end of the assessment period.
When evaluating the consumption of electricity, gas, district heating, and cooling, it is essential to analyze full years of billing data Special attention should be given to instances where the bills reflect electricity or heat generated on-site.
When electricity consumption in rented properties is metered and billed separately, access to energy usage data may be restricted due to data protection regulations In such instances, estimated or conventional values can be utilized, as long as the electricity represents a minor portion of the building's overall energy consumption.
Fuel bills or records of bought fuel are collected.
The fuel level in the tank is recorded at both the start and end of the assessment period using a calibrated scale The amount of fuel consumed during this period is then calculated.
The initial content of the tank at the start of the assessment period, combined with the quantity of fuel purchased during this period, determines the final content of the tank at the end of the assessment period.
Gas consumption in small containers is evaluated by tallying the number of containers utilized If the count is low, the first and last containers used during the assessment period should be weighed to determine the remaining stock.
When a burner operates at a constant power level without modulation and includes a burning time counter, the fuel consumption is calculated by taking the difference between two readings at the start and end of the assessment period, then multiplying that difference by the burner’s fuel flow rate This flow rate must be measured prior to the initial reading and after any adjustments or cleaning of the burner.
The energy use corresponding to the amount of fuel use is obtained by multiplying this amount by its gross calorific value.
The energy content of solid fuels, such as coal and wood, is influenced by their quality and density The most precise method for evaluating this energy content is by weighing the fuel.
E = fuel weight in stock at the beginning of the assessment period fuel weight in stock at end of the assessment period + fuel weight bought during the assessment period
The energy use corresponding to the amount of fuel used is obtained by multiplying this amount by its gross calorific value.
To determine the mass of solid fuel, the volume must be multiplied by the fuel density It is essential to consider the uncertainty of the density when calculating the confidence interval for the mass.
Regularly measuring energy consumption enables the assessment of key building characteristics, including effective boiler efficiency, apparent heat loss coefficient, and equivalent solar collecting area This data can be utilized to calculate the annual energy required for heating.
NOTE Annex D provides more information.
Correction for weather
To ensure that the measured energy rating accurately reflects typical energy consumption, it is essential to adjust the energy use data for weather conditions if the measurement period is less than three full years This correction helps represent the average weather patterns for the building's location or region.
To achieve this, the measured energy use for heating and cooling shall be adjusted to the average weather for the building’s location, i.e the regional climate.
To correct the energy rating, utilize the calculation model outlined in Clause 7 to compute and validate a customized energy rating as per Clause 9 Subsequently, apply the validated model to re-evaluate energy consumption using average local or regional weather data.
Simpler correction methods, as outlined in section 8.2.2.2, can be defined on a national level by considering the assessment's purpose, climate conditions, and the specific types and uses of buildings.
Introduction
This method enhances the confidence level in the building calculation model and the input data by comparing calculated results with actual energy usage It is particularly useful for existing buildings, especially when evaluating the energy efficiency of potential improvement measures.
It is the general method to make corrections or extrapolations to the measured energy use.
Procedure — Validation of the building calculation model
Obtain the measured energy rating according to Clause 8.
Gather essential information, including actual climatic data, air permeability of the building envelope, ventilation rates, heating system efficiencies, and internal conditions such as occupancy and temperatures, from technical documentation or through cost-effective surveys and measurements Refer to sections 9.3 and 9.4 for methods of collecting climatic and occupancy data, respectively, and consult Annex D for energy related to other services It is crucial to estimate the confidence intervals for all collected data, while any unassessable input data should be derived from inference rules, national references, or International Standards.
The assessment period for collecting all data (energy use and input data for the calculation) should be, as far as reasonably possible, the same.
To achieve an accurate tailored rating, it is essential to utilize data that closely reflects real-world conditions, considering factors such as building characteristics, climate, and occupancy Additionally, estimating the confidence interval of the rating is crucial to account for uncertainties in the input data.
Energy carriers utilized for functions beyond heating, cooling, ventilation, hot water, or lighting must be included in the tailored rating If these energy carriers are not individually metered, they should be estimated Additionally, the energy consumed within the conditioned space should be considered as internal heat sources when calculating the tailored rating.
This International Standard does not specify a method for calculating "other services." However, a national-level list of typical energy usage for activities such as cooking, washing, and operating electrical equipment, including computers and production processes, can be provided for different building types Additional information is available in Annex D It is important to compare the measured energy rating with the tailored rating for all energy carriers.
When confidence intervals do not significantly overlap or are excessively large, it is essential to conduct further investigations to verify the data or consider previously overlooked influencing factors The calculations should then be repeated using the revised input data If needed, adjust the input data credibly, ensuring that the calculated energy rating aligns closely with the measured energy rating.
When confidence intervals are both acceptable and significantly overlap, it indicates that the building's calculation model and estimated input data are plausible, allowing for the continuation of the procedure.
Climatic data
Gather external temperature and solar irradiance data from the most representative meteorological station for the building's location and the specific time period used for energy measurement.
Solar irradiance shall be available for all main orientations of the building envelope that include transparent elements or elements covered with transparent insulation.
NOTE 1 Ways of calculating irradiance on any orientation from solar irradiance on a horizontal surface are found in literature 2)
If the altitude of the meteorological station significantly differs from that of the building, external temperatures shall be corrected for altitude according to local average temperature gradients.
NOTE 2 Depending on the climate, the correction is between a 0,5 K and a 1 K decrease per 100 m altitude difference.
Occupancy data
Assessing the actual internal temperature is crucial, as it frequently varies from the design temperature and significantly impacts energy consumption for heating or cooling Various methods can be employed to evaluate this temperature accurately.
In buildings equipped with mechanical ventilation, the air temperature measured in the exhaust duct before the fan can provide a reliable estimate of the average temperature in the ventilated area when the exhaust fan is operational.
In large buildings, a Building Automation and Control System manages energy systems and monitors internal temperature along with other energy-related metrics at various locations, as outlined in Annex A of EN 15232:2007 or the applicable standard in Annex A.
Temperature can be effectively measured and monitored using small single-channel data loggers at select representative locations on days that reflect the meteorological characteristics typical of the corresponding month or season.
— If the heating or cooling systems are controlled by thermostats, their set points could be used, provided that the calibration of the thermostat is checked.
Estimating the external airflow rate is essential and can be achieved through various methods This includes evaluating the airflow rates of air handling units when applicable and employing the tracer gas dilution method as outlined in ISO 12569.
The occupancy (number of occupants) and presence time should be assessed from a survey or from the building management.
To effectively evaluate internal sources of artificial lighting and electrical appliances, it is recommended to analyze electricity bills that do not include heating or cooling systems on the same meter or utilize a submeter In cases where field data for lighting is unavailable, EN 15193 or the applicable International Standard referenced in Annex A can be utilized.
NOTE Not all the electricity used becomes an internal heat source (e.g lights can be placed externally or the heat can be partly exhausted).
2) For example in Duffie and Beckmann, Solar energy thermal processes, John Wiley & Sons, 1974.
Where a separate meter is installed, hot water use is obtained from the difference of two readings at the beginning and end of the assessment period.
NOTE In this case, meters are generally used to include hot water use in bills, from which the information can be obtained without looking at the meters.
In cases where hot water usage is not metered, it should be estimated according to EN 15316-3 or applicable international standards outlined in Annex A This estimation can be based on factors such as the number of occupants, the building's usage, local habits, or data available in national documentation.
Electricity bills may be useful to assess energy use for lighting, provided there are no other systems (cooking, heating, cooling systems, or other appliances) on the same meter.
Otherwise, energy use for fixed built-in lighting is estimated by calculation according to EN 15193 or the relevant International Standard listed in Annex A.