Energy performance of buildings - Application of calculation of energy use to existing buildings

Energy labelling of buildings requires a method valid for both new and existing buildings, and treating them in an equivalent way.
In new buildings all required information exists to compute energy use, when necessary using conventional occupancy data; but the actual energy use is not available. In existing buildings, actual energy use is known in some cases from energy meters, but often some information, such as U-values of components or actual air change rate is missing. Since energy use for space heating and cooling strongly depends on occupants' behaviour and that different uses are involved, actual energy use cannot be used for energy labelling of the building without correction.
Therefore, a methodology should be developed to get the same results from different sets of data. The work will propose a methodology to assess missing data and to calculate a "standard" energy use for space heating and cooling. This work item also includes a methodology that allows determining the energy effectiveness of possible improvements.

Energieeffizienz von Gebäuden - Bewertung des Energieverbrauchs und Festlegung der Leistungsindikatoren

Diese Norm legt die Energieverwendungszwecke fest, die bei der Festlegung von Leistungsindikatoren der Energieeffizienz neuer und bereits bestehender Gebäude zu berücksichtigen sind und enthält Folgendes:
a)   Ein Verfahren zur Berechnung des Zielleistungsindikators, einem Normenergieverwendungszweck, der nicht vom Verhalten der Gebäudenutzer, den tatsächlichen Wetterbedingungen und weiteren tatsächlichen (Umwelt  oder Eingangs )Bedingungen abhängig ist. Für die Anwendung dieses Verfahrens stellen die Gebäudebelegung, das Klima und einige weitere Daten, die nicht vom Gebäude selbst abhängig sind, konventionelle Daten dar, die von der bestimmungsgemäßen Nutzung des Gebäudes und der betrachteten Klimazone abhängen.
b)   Ein Verfahren zur Bewertung des Funktionsleistungsindikators auf der Grundlage der Bezugsenergie.
c)   Eine Verfahrensweise zur Verbesserung des Vertrauens in das Gebäudeberechnungsmodell durch einen Vergleich mit dem tatsächlichen Energieverbrauch.
d)   Ein Verfahren zur Bewertung der Energieeffizienz durch mögliche Verbesserungen.
Es ist die Aufgabe der nationalen Körperschaften festzulegen, unter welchen Bedingungen und für welche Gebäudetypen die verschiedenen Leistungsindikatoren gelten.

Performance énergétique des bâtiments - Evaluation de l'énergie utilisée et définition des indices de performance

Energijske lastnosti stavb – Ugotavljanje porabe energije in definicije ocenitev Energetska učinkovitost stavb

General Information

Status
Not Published
Current Stage
4060 - Closure of enquiry - Enquiry
Due Date
24-Aug-2005
Completion Date
24-Aug-2005

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oSIST prEN 15203:2005SLOVENSKImaj 2005

PREDSTANDARDEnergijske karakteristike stavb – Ugotavljanje porabe energije in definicije ocenitevEnergy performance of buildings - Assessment of energy use and definition of ratings©

Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljenoReferenčna številkaoSIST prEN 15203:2005(en)ICS91.120.10

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMDRAFTprEN 15203March 2005ICSEnglish versionEnergy performance of buildings - Assessment of energy useand definition of ratingsPerformance énergétique des bâtiments - Evaluation del'énergie utilisée et définition des indices de performanceEnergetische Verhalten von Gebäuden - Evaluierung desEnergieverbrauchs von Gebäuden und Definition derLeistungsindikatorenThis draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 89.If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations whichstipulate the conditions for giving this European Standard the status of a national standard without any alteration.This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other languagemade by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the samestatus as the official versions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice andshall not be referred to as a European Standard.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36

B-1050 Brussels© 2005 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. prEN 15203:2005: E

prEN 15203 :2005 (E) 2 Contents Page Foreword..............................................................................................................................................................3 Introduction.........................................................................................................................................................4 1 Scope......................................................................................................................................................5 2 Normative references............................................................................................................................5 3 Terms and definitions...........................................................................................................................7 4 Symbols and abbreviations..................................................................................................................9 5 Assessment of energy use of buildings............................................................................................10 6 Delivered energy, primary energy, emissions and energy costs...................................................14 7 Calculated rating..................................................................................................................................17 8 Operational rating................................................................................................................................19 9 Validated building calculation model................................................................................................22 10 Planning of retrofit measures for existing buildings.......................................................................25 11 Report...................................................................................................................................................26 Annex A (normative)

Methods for collecting building data.........................................................................28 Annex B (normative)

Assessing the used amounts of energyware...........................................................31 Annex C (informative)

Conventional input data related to occupancy......................................................33 Annex D (informative)

Confidence intervals.................................................................................................35 Annex E (informative)

Other uses of energy................................................................................................38 Annex F (informative)

Calorific values of fuels............................................................................................39 Annex G (informative)

Energy monitoring...................................................................................................42 Annex H (informative)

List of possible measures for reducing energy use.............................................45

prEN 15203:2005 (E) 3 Foreword This document (prEN 15203:2005) has been prepared by Technical Committee CEN/TC 89 “Thermal

performance of buildings and building components”, the secretariat of which is held by SIS. This document is currently submitted to the CEN Enquiry. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s).

prEN 15203 :2005 (E) 4 Introduction Energy assessments of buildings are carried out for various purposes, such as: a) Judging compliance with building regulations expressed in terms of a limitation on energy use or a related quantity; b) Transparency in commercial operations through the certification and/or display of a level of energy performance (energy certification); c) Monitoring of the energy efficiency of the building including heating, ventilation and air conditioning systems d) Helping in planning retrofit measures, through prediction of energy savings which would result from various actions. Energy certification of buildings requires a method that is applicable to both new and existing buildings, and which treats them in an equivalent way. Therefore, a methodology to obtain equivalent results from different sets of data is presented in this standard. A methodology to assess missing data and to calculate a "standard" energy use for space heating and cooling, ventilation, domestic hot water and lighting is provided. This standard also includes a methodology that allows assessment of the energy effectiveness of possible improvements.

Two principal types of ratings for buildings are proposed in this standard: 1) The asset rating is obtained by calculation for standardised conditions, but there can be different ways of assembling the input data – from drawings and design values for new buildings, from drawings, site surveys and rules derived from building typology for existing buildings, and by improving on the latter by making use of metered energy. 2) The operational rating is obtained by metering and summing up all delivered energywares.

Because of the differences in the way these two ratings are obtained, they cannot be compared directly. However, the difference between the two ratings for the same building can be used to assess the cumulative effects of actual construction, systems and operating conditions versus standard ones and the contribution of energy uses not included in the asset rating.

prEN 15203:2005 (E) 5 1 Scope This standard defines the uses of energy to be taken into account for setting energy performance ratings for new and existing buildings, and provides: a) A method to compute the asset rating, a standard energy use that does not depend on occupant behaviour, actual weather and other actual (environment or input) conditions. For this, occupancy, climate and some other data that do not depend on the building itself are conventional ones, depending on the intended use of the building and on the climatic zone considered.

b) A method to assess the operational rating, based on the delivered energy.

c) A methodology to improve confidence in the building calculation model by comparison with actual energy consumption. d) A method to assess the energy effectiveness of possible improvements. It is up to national bodies to define under which conditions and for which types of buildings the various ratings apply. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 410, Glass in building – Determination of luminous and solar characteristics of glazing EN 673, Glass in building – Determination of thermal transmittance (U value) – Calculation method EN 12412-2, Thermal performance of windows, doors and shutters – Determination of thermal transmittance by hot box method – Part 2: Frames EN 13187, Thermal performance of buildings – Qualitative detection of thermal irregularities in building envelopes – Infrared method prEN wi 1+3, Energy performance of buildings — Methods for expressing energy performance and for energy certification of buildings prEN wi 2, Energy performance of buildings — Overall energy use, primary energy and CO2 emissions prEN wi 7, Heating systems in buildings – Method for calculation of system energy requirements and system efficiencies – Part 1: General prEN wi 8, Heating systems in buildings – Method for calculation of system energy requirements and system efficiencies – Part 2.1: Space heating emission systems prEN wi 9, Heating systems in buildings – Method for calculation of system energy requirements and system efficiencies –

Part 2.2.1: Boilers
Part 2.2.2: Heat pumps
Part 2.2.3: Heating generation – Thermal solar systems
Part 2.2.4: Performance and quality of CHP
Part 2.2.5: Performance and quality of district heating and large volume systems
Part 2.2.6: Performance of other renewables (heat and electricity)

Part 2.2.7: Space heating generation – Biomass combustion systems prEN wi 10, Heating systems in buildings - Method for calculation of system energy requirements and system efficiencies – Part 2.3: Space heating distribution systems

prEN 15203 :2005 (E) 6 prEN wi 11, Heating systems in buildings – Method for calculation of system energy requirements and system efficiencies – Part 3.1: Domestic hot water systems, including generation efficiency and the tap water requirements prEN wi 12, Calculation of room temperatures and of load and energy for buildings with room conditioning systems prEN wi 13, Energy performance of buildings – Energy requirements for lighting — Part 1: Lighting energy estimation prEN wi 14, Energy performance of buildings – Calculation of energy use for space heating and cooling prEN wi 17, Thermal performance of buildings – Calculation of energy use for space heating and cooling – General criteria and validation procedures for detailed calculations prEN wi 20+21, Ventilation for buildings – Calculation methods for energy requirements due to ventilation systems in buildings prEN wi 22, Calculation methods for energy efficiency improvements by the application of integrated building automation systems prEN ISO 6946:2005, Building components and building elements – Thermal resistance and thermal transmittance – Calculation method

EN ISO 7345, Thermal insulation – Physical quantities and definitions

prEN ISO 10077-1:2004, Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: General EN ISO 10077-2, Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 2: Numerical method for frames prEN ISO 10211:2005, Thermal bridges in building construction – Heat flows and surface temperatures – Detailed calculations EN ISO 12567 (all parts), Thermal performance of windows and doors – Determination of thermal transmittance by hot box method EN ISO 12569, Thermal insulation in buildings – Determination of air change in buildings - Tracer gas dilution method EN ISO 13790, Thermal performance of buildings – Calculation of energy use for space heating prEN ISO 14683:2005, Thermal bridges in building construction – Linear thermal transmittance – Simplified methods and default values EN ISO 15927-41), Hygrothermal performance of buildings – Calculation and presentation of climatic data – Part 4: Hourly data for assessing the annual energy use for heating and cooling

prEN ISO 15927-6:2004, Hygrothermal performance of buildings – Calculation and presentation of climatic data – Part 6: Accumulated temperature differences (degree-days)

ISO 9869, Thermal insulation – Building elements – In-situ measurement of thermal resistance and thermal transmittance

ISO 13600, Technical energy systems – Basic concepts ISO 13601, Technical energy systems – Structure for analysis – Energyware supply and demand sectors

1) To be published.

prEN 15203:2005 (E) 7 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in EN ISO 7345 and the following apply. 3.1 rating evaluation of the energy performance of a building based on the weighted sum of the calculated or metered use of energy carriers. 3.2 asset rating rating based on calculations of the energy used by a building for heating, cooling, ventilation, hot water and lighting, with standard input data related to internal and external climates and occupancy NOTE It represents the intrinsic energy potential of a building under standardised conditions of weather and occupancy This is particularly relevant to certification of standard performance. The asset rating represents a weighted sum per energyware of the total energy for heating, hot water heating, cooling, ventilation and lighting. This rating quantifies the calculated energy intensity of the building under standardised conditions for a given set of energy end uses. 3.3 design rating rating based on calculations using building drawings and design values, calculated for a building at the design phase

NOTE The design rating is calculated on the basis of building plans, whereas the asset rating is calculated using data for the building as actually constructed. 3.4 tailored rating rating based on calculations of the energy used by the building for heating, cooling, ventilation, hot water and lighting, with actual climate and occupancy data 3.5 operational rating rating based on measured energy use

NOTE The operational rating is the weighted sum of all energywares used by the building. It is a measure of the in-use performance of the building. This is particularly relevant to certification of actual performance The operational rating represents the sum per energyware of the total energy used by the building, as measured by meters or other means described in Annex B. This rating quantifies the total actual energy use of the building. 3.6 building inhabited construction as a whole, including its envelope,

and heating, ventilation and air conditioning systems 3.7 new building building at design stage or under construction or (for operational rating) too recently constructed to have reliable records of energy use 3.8 existing building building that is erected, for which actual data necessary to assess the energy use according to this standard are known or can be measured

3.9 building calculation model mathematical model of the building used to calculate its energy use

prEN 15203 :2005 (E) 8 NOTE Most models used in this standard are defined in international standards. Several models may be necessary to assess the energy use for all purposes.

3.10 validated building calculation model building calculation model in which one or more parameters are adjusted so that its results do not significantly differ from the measured reality

3.11 confidence interval interval that has a high probability (e.g. 95 %) to include the actual value

NOTE Annex D provides ways to assess such intervals. 3.12 reasonably possible can be achieved at a reasonable cost

3.13 reasonable cost investment that is accepted by all parties to reach a given purpose

NOTE This cost strongly depends on the purpose of the effort. For example, the cost of a rating could be relatively large if it is to provide an official certificate to put the building on the market or for displaying the building performance to the public, but reduced if it is simply for statistical purpose.

3.14 energy carrier substance or phenomenon that can be used to produce mechanical work or heat or to operate chemical or physical processes [ISO 13600:1997] 3.15 energyware tradable commodity used mainly to produce mechanical work or heat, or to operate chemical or physical processes, and listed in Annex A of ISO 13600. [ISO 13600:1997] NOTE Energywares form a proper subset of energy carriers. The set of energy carriers is open. 3.16 energyware consumption system technical energy system consuming energyware and in many cases also other energy carriers and producing products and services [ISO 13600:1997] NOTE Buildings are such systems.

3.17 renewable energy

energy from sources that will not be exhausted during the lifetime of mankind, such as solar energy (thermal and photovoltaic), wind, hydraulic, biomass

NOTE In ISO 13602-1:2002, renewable resource is defined as 'natural resource for which the ratio of the creation of the natural resource to the output of that resource from nature to the technosphere is equal to or greater than one. 3.18 primary energy

energy that has not been subjected to any conversion or transformation process

NOTE For a building, it is the energy used to produce the energy delivered to the building. It is the delivered energy divided by the conversion or transformation factor of each form of energy.

prEN 15203:2005 (E) 9 3.19 delivered energy energy supplied to the building from the last market agent

NOTE The boundaries of the building include all internal and external areas associated with the building, where energy is consumed or produced (see 5.1). The energy produced by the building itself, for example using solar water heater, photovoltaic systems or co-generation and delivered back to the market is reported separately. Delivered energy is presented per energyware. 3.19 energy use of a building total energy per energy carrier delivered to the energy systems for heating, cooling, ventilation, hot water heating, lighting, appliances, etc.

NOTE Appliances are not explicitly included in the asset rating and in the ‘inter alia’ subset of energy end uses in Article 2 of the EPBD2) , but they are in fact included in the total energy use of the building. 3.20 auxiliary energy energy used by heating, cooling, domestic water, lighting and ventilation systems to transform the delivered energy into the useful energy

NOTE This includes energy for fans, pumps, pilot flames, electronics, etc., but not the energy that is transformed. 3.21 calorific value quantity of heat produced by complete combustion, at a constant pressure equal to 101 320 Pa, of a unit amount of fuel

NOTE The gross calorific value includes the heat recovered when condensing the water vapour resulting from the combustion of hydrogen. The net calorific value does not take account of this latent heat.

4 Symbols and abbreviations Table 1 —Symbols and units Symbol Quantity Unit A area m² c concentration - C cost € DD accumulated temperature differences (degree-days) K d f factor

- I solar irradiance J/m² E energyware amount kg, m³, kWh, MJ, etc. O occupancy h, h/d, % Q quantity of heat or energy J t time, time interval d, h, s V& airflow rate m³/h, m³/s Φ

heat flow rate, power W GCV gross calorific value of an energyware MJ/unit, kWh/unit θ

Celsius temperature °C

2) DIRECTIVE 2002/91/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 December 2002 on the energy performance of buildings

prEN 15203 :2005 (E) 10 NOTE

Hours can be used as the unit of time instead of seconds for all quantities involving time (i.e. for time periods as well as for air change rates), but in that case the unit of energy is Watt-hours [Wh] instead of Joules. Table 2 — Subscripts a automation and control m measured c cooling n net CO2 related to CO2 emissions o operational d Delivered, day p primary E electricity rc recovered e external rn renewable ex exported s system g Related to gains st standard h heating t total i internal v ventilation i,j,k numbering indices w hot water L limit Y year, annual l lighting

5 Assessment of energy use of buildings 5.1 Building boundaries The boundaries for the energy performance assessment shall be clearly defined for all energy carriers before the calculation. It includes all inside and outside areas associated with the building, where energy is consumed or produced. For insulated buildings, it is defined by the building envelope for heat flows, the main building meters for gas, electricity, district heating and water, the loading port of the storage facility for liquid and solid energywares, and the smoke exhaust of chimney and connection to main wastewater duct for losses.

If a part of a building system (e.g..boiler, chiller, cooling tower, etc.) is outside the building envelope, it is nevertheless considered to be inside the boundaries. A building may refer to a group of adjacent buildings as a whole or parts thereof that have been designed or altered to be used separately. If one building in a row of similar buildings are to be assessed, heat flows through partition walls are neglected in the balance. If adjacent buildings do not have the same type of use, and hence not the same internal design or actual temperature, heat flows through partition walls are taken into account in the balance. NOTE In many cases, buildings in rows have the same use and, for calculation purposes, the internal temperature of all the buildings can be assumed to be the same, and these partition walls can be taken to be adiabatic. However, if the external envelope is well insulated and partition walls are not, these heat flows can contribute an appreciable amount of heat gains and losses. The way the building envelope is considered to calculate heat flows is defined in prEN wi 14. 5.2 Types of ratings This standard proposes two principal options for energy rating of buildings, the first being calculated, the second being based on measurements. These options are the asset rating and the operational rating.

prEN 15203:2005 (E) 11

Figure 1 — The operational rating includes all energy uses under actual conditions, while the asset rating includes only some uses, and for standard conditions The asset rating is based on calculations of the energy used by the building for heating, cooling, ventilation, hot water and lighting, with standard input data related to climate and occupancy (see 7.2). This rating provides an assessment of the energy efficiency of the building under standardised conditions that enables a comparison to be made between different buildings within climatic main regions and with identical or at least similar activities.

The operational rating is based on measurement of energy use (see Clause 8). The operational rating measures the in-use performance of a building, including all deviations between theoretical properties in calculations and realised properties (air-infiltration, heat transfer, generation efficiency, control, etc.) and is influenced by the way the building is maintained and operated. It cannot therefore be used to provide prospective purchasers or tenants with like-for-like comparisons between buildings. It assists those trying to improve the efficiency of building operation and allows displaying the actual energy performance of a building. It can also provide useful feedback to the owners, occupiers and designers of new buildings if assessed a few years after occupation and compared to the calculated asset rating, for the same set of energy end uses. Only asset rating and operational ratings are used for building energy performance certification. The design rating is similar to the asset rating, but based on building drawing and design intentions. It can be used to get a building permit. The tailored rating is an asset rating, in which either actual climatic data or actual occupancy related data or both are used instead of standard ones. This can be used to compare two buildings having different climates or different uses, to compare retrofit scenarios, to optimise energy performance, etc.

The calculation models and input used for the asset rating can be validated against the operational rating, providing more confidence in the model (see Clause 9). The validated model can then be used to compute a more accurate asset rating, or to study the effect of retrofit scenarios. The types of rating are summarised in Table 3. The type of rating (asset rating or operational rating) to be used for certification of different building types is defined in national regulations. Table 3 —Types of ratings

Input data

Name Use Climate Building Utility or purpose Design Standard StandardDrawings Building permit Asset Standard StandardActual Certificate, regulation Calculated Tailored Depending on purposeActual Optimisation, comparisons, retrofit planning Measured Operational Actual Actual Actual Certification, regulation

prEN 15203 :2005 (E) 12 5.3 Input and output 5.3.1 General This standard needs and provides the following information: 5.3.2 Necessary inputs 5.3.2.1 Inputs for calculated ratings a) Annual energy use for heating, calculated according to prEN wi 14; b) Annual energy use for cooling, calculated according to prEN wi 14; c) Annual energy use for hot water, calculated according to prEN wi 11; d) Annual energy use for lighting, calculated according to prEN wi 13; e) Annual energy use for ventilation, calculated according to prEN wi 20; f) Effect of automation and controls, assessed according to prEN wi 22; g) Conversion factors from delivered energy to primary energy and CO2 production, according to prEN wi 2. 5.3.2.2 Inputs for operational rating and calculation model validation h) Metered energy use for all energywares. 5.3.3 Additional inputs

The following information is normally provided on a national level: i) Gross calorific value of energywares; j) Standard data related to occupancy (temperature, humidity, airflow rate, internal gains, hot water use, and standard energy use for appliances other than heating, cooling, ventilation, hot water and lighting); k) Standard climatic data.

prEN 15203:2005 (E) 13
Figure 2 — Inputs to this standard and outputs from this standard

5.3.4 Provided output For certification and regulation purposes this standard provides: l) Asset rating: the calculated energy use of the building under standard conditions; m) Operational rating, based on metered energy use; For obtaining building permits this standard provides: n) Design rating; For other purposes this standard provides: o) Validated building calculation model that can be used to assess the effect of measures to be taken for improving the energy performance, including combinations thereof; p) Tailored rating. These outputs are used for expressing the energy performance of the building and establishing energy performance requirements according to prEN wi 1+3.

prEN 15203 :2005 (E) 14 6 Delivered energy, primary energy, emissions and energy costs 6.1 Energy uses The total calculated energy used by the building shall comprise the annual energy use for the following purposes:  heating;  cooling;  ventilation systems;  hot water;  lighting. Each energy use includes auxiliary energy and losses of systems.

Energy uses for other purposes (e.g. electrical appliances, cooking, industrial processes) are not included in the calculated energy use but the total metered energy will normally include these other uses. 6.2 Delivered energy 6.2.1 General For each of the purposes listed in 6.1, the energy use is calculated for standardised use and climate according to the standards cited in 6.2.2. The results are allocated to energy carriers for each purpose according to the scheme in Table 4. The rows and columns in Table 4 should be adapted to the building concerned. The columns include the relevant energy carriers. The sub-total row relates to the energy included in the asset rating.

If energy is produced on site, rows and columns are added to the matrix for each energy producing system. Delivered energy consumed by the systems (e.g. gas for cogeneration) is indicated in the appropriate cell under "energy consumption", and energy produced by a system is indicated by a negative number in the appropriate cell under "energy production". Energy produced and consumed on site is indicated by a positive number in the cell corresponding to the appropriate use. A negative number in the total row means energy being exported.

Exported amounts of energy carriers (electricity or heat in most cases) are accounted separately, because different conversion factors may apply to them. System heat losses that are recovered are, depending on the way they are recovered, either deducted from the loss of each system or taken into account as gains to calculate energy use for heating and cooling. NOTE In buildings with co-generation, it is not straightforward to attribute the fuel used to the heat and electricity produced and the system loss. This splitting should nevertheless be performed as well as reasonably possible. The calculation for heating and cooling is based on a mathematical cal

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