ISO/TR 52003-2:2017

Energy performance of buildings - Indicators, requirements, ratings and certificates - Part 2: Explanation and justification of ISO 52003-1

ISO/TR 52003-2:2017 refers to ISO 52003‑1. It contains information to support the correct understanding and use of ISO 52003‑1 and does not contain any normative provisions. NOTE The relation with other EPB standards, product standards and product policy is shown schematically in Figure 4 of Clause 6.

Performance énergétique des bâtiments — Indicateurs, exigences, classification et certificats — Partie 2: Explication et justification de l'ISO 52003-1

General Information

• Status: Published
• Publication Date: 20-Jun-2017
• ICS: 91.120.10 - Thermal insulation of buildings
• Technical Committee: ISO/TC 163 - Thermal performance and energy use in the built environment
• Drafting Committee: ISO/TC 163/WG 4 - Joint ISO/TC 163 - ISO/TC 205 WG: Energy performance of buildings using holistic approach
• Parallel Committee: ISO/TC 205 - Building environment design
• Current Stage: 6060 - International Standard published
• Start Date: 21-Jun-2017
• Due Date: 20-Mar-2017
• Completion Date: 20-Mar-2017

Overview

ISO/TR 52003-2:2017 is an informative technical report that accompanies ISO 52003-1 and explains the background, rationale and correct use of the normative requirements in Part 1. It does not contain normative provisions itself; instead it provides guidance, clarifications and worked examples to support consistent implementation of the energy performance of buildings (EPB) framework for indicators, requirements, ratings and certificates.

The report situates ISO 52003-1 within the wider EPB standards family and clarifies relationships with product standards and product policy (see Clause 6, Figure 4). It also supplies templates, illustrations and annex procedures to help implementers apply the standard in practice.

Key Topics

• Purpose and scope: Explanation and justification of the concepts used in ISO 52003-1; informative only.
• Document description and selection criteria: Guidance on choosing among options and methods described in Part 1.
• Input and output data: Recommended data items and reporting templates for consistent EPB calculations and declarations.
• EPB feature relationships: How features, indicators, requirements, ratings and certificates interrelate.
• Energy performance indicators: Overall and partial performance metrics, normalization (e.g., to floor area) and use of ratios.
• Tailoring and requirements: Approaches to tailor requirements and ratings for project characteristics, new versus existing buildings, and tightening over time.
• EPB rating & reference values: Procedures for defining rating scales, reference points and classification methods.
• Energy performance certificates (EPCs): Recommended content, graphical models and procedural steps for issuing certificates.
• Quality control and compliance check: Guidance on verification, reporting and ensuring conformity.
• Informative annexes: Templates for input/method selection, default choices, variable-value illustrations, classification procedures and an energy label model.

Applications

ISO/TR 52003-2:2017 is practical guidance for:

• Policy makers and regulators implementing EPB requirements into building codes.
• Energy assessors and certifiers preparing energy performance certificates (EPCs).
• Building designers and consultants applying EPB indicators and tailoring requirements to projects.
• Software developers creating compliance and calculation tools aligned with ISO 52003-1.
• Building owners and facility managers interpreting ratings and certificates for retrofit or procurement decisions.

The report helps ensure consistent, transparent and defensible use of EPB indicators, ratings and certificates across climates, building types and jurisdictions.

Related standards

• Normative companion: ISO 52003-1 (Part 1 - normative requirements)
• Overarching EPB: ISO 52000-1
• Supporting technical rules: CEN/TS 16628, CEN/TS 16629
• Historical references: EN 15217, ISO 16343

Keywords: ISO/TR 52003-2:2017, energy performance of buildings, EPB, indicators, ratings, certificates, ISO 52003-1, energy performance certificate, building energy performance.

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 52003-2
First edition
2017-06
Energy performance of buildings —
Indicators, requirements, ratings and
certificates —
Part 2:
Explanation and justification of ISO
52003-1
Performance énergétique des bâtiments — Indicateurs, exigences,
classification et certificats —
Partie 2: Explication et justification de l’ISO 52003-1
Reference number
©
ISO 2017
ISO/TR 52003-2:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
Contents Page
Foreword .v
Introduction .vi
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Symbols and abbreviations . 1
4.1 Symbols . 1
4.2 Subscripts . 2
5  Description of the document . 2
5.1 General . 2
5.2 Selection criteria between possible options. 4
5.3 Input and output data . 4
6  Relation between EPB features, indicators, requirements, ratings and certificates .4
7  Energy performance features and their indicators . 9
7.1 General . 9
7.2 Normalization to building size . 9
7.3 Energy performances and their indicators . 9
7.3.1 Overall energy performances. 9
7.3.2 Partial energy performances . 9
7.4 Ratios of identical/similar quantities as indicators for energy performances . 9
8  Tailoring for requirements and for ratings .10
8.1 Two approaches .10
8.2 Project characteristics for tailoring .12
9 Energy performance requirements .13
9.1 General .13
9.2 Choice of the mix of requirements .14
9.2.1 General.14
9.2.2 New buildings .14
9.2.3 Existing buildings (renovations and extensions) .15
9.3 Constant or variable value requirements .15
9.3.1 Tailoring requirements to individual project characteristics .15
9.3.2 Tightening the requirements over time .17
9.4 Actual strictness . .17
9.5 Reporting template for the overall energy performance .18
10  EPB rating .18
10.1 General .18
10.2 EPB rating procedures .18
10.2.1 Reference point - National legal requirements for new buildings .19
10.2.2 Expressions of reference point of the scale .19
10.2.3 Proposal for the shape of the scale .20
10.2.4 Conclusions on Method 2 .21
10.3 Reference values .21
11  Energy performance certificate .21
11.1 General .21
11.2 Content of the procedure for a building energy certificate .21
11.3 Content of the energy performance certificate .21
11.3.1 General.21
11.3.2 Default graphical representation model .22
11.4 Recommendations .22
ISO/TR 52003-2:2017(E)
12 Quality control .22
13  Compliance check .23
Annex A (informative) Input and method selection data sheet — Template.24
Annex B (informative) Input and method selection data sheet — Default choices .25
Annex C (informative) Illustration of the variable value of the overall primary energy use
per floor area for a given set of technical measures .27
Annex D (informative) Procedure for building energy performance classification .30
Annex E (informative) Energy label model .31
Bibliography .34
iv © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL:
w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use
in the built environment, in collaboration with ISO/TC 205, Building environment design, and with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 89, Thermal performance
of buildings and building components, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 52003 series can be found on the ISO website.
ISO/TR 52003-2:2017(E)
Introduction
Relation between this document and the accompanying International Standard
For proper understanding of the present document, it is necessary to read it in close conjunction,
clause by clause, with ISO 52003-1. First, the corresponding clause in Part 1 needs to be read; then
the complementary information in the same clause in this report can be read. Essential information
provided in Part 1 is not repeated in this part. References to a clause refer to the combined content of
[14] [15]
that clause in both parts 1 and 2. Brief articles on the subject can be found in and .
The set of EPB standards, technical reports and supporting tools
In order to facilitate the necessary overall consistency and coherence, in terminology, approach,
input/output relations and formats, for the whole set of EPB-standards, the following documents and
tools are available:
a) a document with basic principles to be followed in drafting EPB-standards: CEN/TS 16628:2014,
[6]
Energy Performance of Buildings - Basic Principles for the set of EPB standards ;
b) a document with detailed technical rules to be followed in drafting EPB-standards:
CEN/TS 16629:2014, Energy Performance of Buildings - Detailed Technical Rules for the set of EPB-
[7]
standards ;
The detailed technical rules are the basis for the following tools:
1) a common template for each EPB standard, including specific drafting instructions for the relevant
clauses;
2) a common template for each technical report that accompanies an EPB standard or a cluster of EPB
standards, including specific drafting instructions for the relevant clauses;
3) a common template for the spreadsheet that accompanies each EPB (calculation) standard, to
demonstrate the correctness of the EPB calculation procedures.
Each EPB standard follows the basic principles and the detailed technical rules and relates to the
[10]
overarching EPB standard, ISO 52000-1 .
One of the main purposes of the revision of the EPB standards has been to enable that laws and
regulations directly refer to the EPB standards and make compliance with them compulsory. This
requires that the set of EPB standards consists of a systematic, clear, comprehensive and unambiguous
set of energy performance procedures. The number of options provided is kept as low as possible,
taking into account national and regional differences in climate, culture and building tradition, policy
and legal frameworks (subsidiarity principle). For each option, an informative default option is provided
(Annex B).
Rationale behind the EPB Technical Reports
There is a risk that the purpose and limitations of the EPB standards will be misunderstood, unless
the background and context to their contents – and the thinking behind them – is explained in some
detail to readers of the standards. Consequently, various types of informative contents are recorded
and made available for users to properly understand, apply and nationally or regionally implement the
EPB standards.
If this explanation would have been attempted in the standards themselves, the result is likely to be
confusing and cumbersome, especially if the standards are implemented or referenced in national or
regional building codes.
vi © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
Therefore each EPB standard is accompanied by an informative technical report, like this one, where
all informative content is collected, to ensure a clear separation between normative and informative
[7]
contents (see CEN/TS 16629 ):
— to avoid flooding and confusing the actual normative part with informative content;
— to reduce the page count of the actual standard; and
— to facilitate understanding of the set of EPB standards.
[12]
This was also one of the main recommendations from the European CENSE project that laid the
foundation for the preparation of the set of EPB standards.
This document
This document accompanies ISO 52003-1, which forms part of the set of EPB standards.
The role and the positioning of the accompanying standard in the set of EPB standards is defined in the
Introduction to ISO 52003-1.
Accompanying spreadsheet(s)
Because in the accompanying document ISO 52003-1 no calculation procedures are defined, an
accompanying calculation spreadsheet is not relevant.
History of this document and the accompanying International Standard
[2]
The first standard on this topic was EN 15217:2007 . It was developed as part of Mandate 343 of the
[3] [4]
EC to CEN to support the EPBD (2003) . An upgrade of it was published as ISO 16343:2013 . The
document has been thoroughly reworked and split in a normative International Standard (Part 1) and
[5]
the present informative document (Part 2) as part of Mandate 480 of the EC to CEN .
TECHNICAL REPORT  ISO/TR 52003-2:2017(E)
Energy performance of buildings — Indicators,
requirements, ratings and certificates —
Part 2:
Explanation and justification of ISO 52003-1
1  Scope
This document refers to ISO 52003-1. It contains information to support the correct understanding and
use of ISO 52003-1 and does not contain any normative provisions.
NOTE The relation with other EPB standards, product standards and product policy is shown schematically
in Figure 4 of Clause 6.
2  Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
More information on the use of EPB module numbers for normative references between EPB standards
[11]
is given in ISO/TR 52000-2 .
ISO 52003-1:2017, Energy performance of buildings – Indicators, requirements, ratings and certificates –
Part 1: General aspects and application to the overall energy performance
3  Terms and definitions
For the purposes of this document, the terms and definitions given in the accompanying EPB document,
ISO 52003-1, apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
[11]
More information on some key EPB terms and definitions is given in ISO/TR 52000-2 .
4  Symbols and abbreviations
4.1  Symbols
For the purposes of this document, the symbols given in ISO 52003-1 and the following apply.
ISO/TR 52003-2:2017(E)
[11]
More information on key EPB symbols is given in ISO/TR 52000-2 .
Symbol Name of quantity Unit
A area m²
c constant a)
f factor -
f shape factor -
V volume m³
a) varies with the context
4.2  Subscripts
For the purposes of this document, the subscripts given in ISO 52003-1 and the following apply.
More information on key EPB subscripts is given in ISO/TR 52000-2.
c conditioned
env envelope
use useful
5  Description of the document
5.1  General
Figure 1 shows in a first, simplified step and in a schematic manner, the main uses that can be made of
the EPB indicators.
EPB indicators are numeric quantities that are the intermediate or final output of the EPB assessment
standards (see also Figure 4 in Clause 6). They can be the result of either calculations (e.g. a thermal
transmittance value) or of measurements (e.g. the air tightness value of the thermal envelope) or a
combination of both (e.g. an overall energy performance value that is partly based on a measured air
tightness). Ideally, all mathematical operations of a technical variable are defined in the EPB assessment
standards and the value as such (and its definition) are directly ready for further use, without the need
for further mathematical manipulation.
The EPB indicators can be used in several different ways by public and private actors. A first major
use of EPB indicators is to impose regulatory EPB requirements on construction works of all kinds. A
second major use is to rate the energetic quality of the considered EPB feature through comparison
with benchmarks. The EPB requirements can serve as one of the references for the rating. There can
still be other uses, such as the use of a variable as target function for design optimization, e.g. the least
life cycle cost.
Selected EPB indicators, ratings, requirements and their (non)compliance (if applicable), and other
information (such as recommendations for improvement of the energy performance) can be included in
the EPB certificate, and its detailed report.
2 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
Figure 1 — Simplified schematic overview of the relations between various EPB aspects
Figure 2 illustrates in dotted lines potential additional interactions. In order to achieve equitable
requirements or ratings, it can be necessary for many indicators to use in a first instance variable
values as requirement or reference. Such variable values are tailored to the characteristics of each
individual project. For ease of communication, the primary indicator can be converted in a second
instance into a derived indicator by taking its ratio to the variable requirement or reference value. The
derived, secondary indicator then again allows the requirement or rating reference to be a constant
value, which can greatly facilitate communication. Generally speaking, it seems desirable that all
mathematical operations are defined in the actual EPB assessment standards. But for derived indicators
that are intrinsically related to the (requirement and rating) policy choices, the last few mathematical
calculations inevitably can only be defined in a regulatory context.
Figure 2 — Full schematic overview of the relations between various EPB aspects
ISO/TR 52003-2:2017(E)
5.2  Selection criteria between possible options
No additional information beyond the accompanying document.
5.3 Input and output data
No additional information beyond the accompanying document.
6  Relation between EPB features, indicators, requirements, ratings and
certificates
The conceptual table of Figure 3 is an alternative to the presentation in Figure 2. It allows a user to
visualize and report the practical choices that a given (public or private) actor makes with respect to its
uses of the EPB indicators.
On top of each of the columns of the table, the number of the clause in ISO 52003-1 and ISO/TR 52003-2
that deals with the particular aspect is given.
In the first column, the different EPB features can be listed. (For reasons of sizing, here these are
done in an exemplary, non-exhaustive manner.) They can be grouped in 3 categories: overall energy
performances, partial energy performances and the energy performances of products (“traded
commodities”).
NOTE 1 The product group can of course include devices that are not used in buildings (e.g. vehicles) or that
are not always considered in the building energy performance assessment (for instance, the energy use of plug-
in appliances such as refrigerators, televisions, computers etc., is usually not included in the calculations of the
energy use of the building, but is usually part of the measured overall building energy performance).
In the second column, the possible indicators for each of the EPB features can be listed.
Clause 7 Clause 7 Clause 9 Clause 10 -
EPB feature indicator requirements rating other uses
new existing
OVERALL ENERGY
PERFORMANCES
primary energy use X
non-renewable pri- X
mary energy use
...
PARTIAL ENERGY
PERFORMANCES
... ...
lighting LENI
...
fans
specific fan power
...
systems
efficiency X
expenditure factor
... ...
heating need
...
4 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
Clause 7 Clause 7 Clause 9 Clause 10 -
EPB feature indicator requirements rating other uses
new existing
cooling need
...
envelope airtight-
ness
specific air leakage
...
overall thermal mean thermal
insulation transmittance
component ther-
mal insulation
thermal X
transmittance
temperature factor
...
PRODUCT
ENERGY
PERFORMANCES
...
boilers
pumps
fans
...
refrigerators X
televisions
...
vehicles
...
Figure 3 — Tabular overview of the relation between various EPB aspects
The third column concerns requirements. It is subdivided into 2 sub-columns, dealing with new
construction on the one hand and works in existing buildings on the other hand. With a cross, the EPB
indicators for which requirements are set can be indicated. These can differ between new construction
(focus typically on one or more overall EPB indicators) and works in existing buildings (by their nature,
focus typically on the elements and systems that are the object of the works).
In the fourth column crosses can indicate the indicators that are rated.
The empty fifth column reminds that there can be many more uses for the EPB indicators. The column
can be replaced by several columns if the purpose is to illustrate/document practical instances where
such other uses apply.
In Figure 4, the further relation with the assessment methods is shown. The arrows in the figure
represent the transfer of data (output of 1 module is input for 1 or more other modules) towards the
final use of a result (e.g. as indicator).
Product standards assess basic characteristics either by measurement or calculation, or a combination
of both. Sometimes there is for a given product an alternative, free choice between measurement and
calculation methods (e.g. the thermal transmittance of glazing). This choice is represented by the ellipse
in Figure 4. Product calculation methods usually rely on measured features of its composing elements
(e.g. coating with low thermal emissivity in glazing, or dimensions of a frame) or on production control
ISO/TR 52003-2:2017(E)
schemes (e.g. noble gas filling in glazing). The product characteristics thus assessed can be used either
directly as indicator (e.g. full and part load efficiencies of a boiler) or combined in a further calculation
model to give a more comprehensive assessment (e.g. typical seasonal efficiency, taking into account
auxiliary energy use).
On-site measurements and inspections can evaluate a building as a whole or its various elements and
subsystems as they are effectively built/installed, sometimes also including the way they are used
(controller settings, user behaviour, etc.). Examples are:
— measurement of the air tightness of the envelope or of the ducts;
— measurement of ventilation flow rates;
— measurement of boiler efficiency; and
— measurement of the overall energy uses, etc.
These measurement results can be used directly as indicator (or after minor further processing, e.g.
conversion of delivered to primary energy) and/or they can serve as input for EPB calculations.
The EPB calculation standards are an extensive set of calculation models with multiple interactions
among them. The ultimate output are overall energy performance indicators, but a very large number
of intermediate results can potentially be used as partial energy performance indicators and can serve
a useful purpose at some time.
NOTE 2 For this reason, it seems desirable that all (i.e. both final and intermediate) results are explicitly
reported in full detail as calculation output of any EPB calculation programme. This includes each and every
one of the internal variables that are defined in the EPB methods. In this manner also full transparency and
traceability is created.
All the diverse input for the EPB calculations (input arrows at the bottom of the large EPB calculation
triangle in Figure 4 can be grouped in some major categories:
— Annex A choices (for each of the different EPB standards):
— in the context of regulations specified by the competent authorities;
— in private contexts: own specifications (tailored).
— product data
— project specific features:
— geometry (areas, layer thicknesses, orientations, et cetera.);
— types of controls;
— measured features (e.g. air tightness of the thermal envelope);
— external shading, etc.
— other.
NOTE 3 The arrows at the right hand side in Figure 4 indicate the typical application range of (energy
performance of building regulations and product regulations. Generally speaking, overlap of both does not seem
productive.
However, in some instances, overlaps can occur in a useful manner. For instance, the product regulations
can set a general requirement for a given type of product (e.g. boilers) on the market, but the building
6 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
regulation can impose a stricter requirement when a boiler is installed in a very cold region of the
1)
jurisdiction .
Vice-versa, product regulations can impose requirements on the application-related aspects of products
(and thus not merely the putting on the market as such of the product), e.g. that a certain type of device
always be used with a minimal control, even though the control system is not necessarily integral part
of the device.
NOTE 4 Generally speaking, it appears desirable that a calculation model for a given product is identical (or
at least maximally parallel) when used for determining the product indicator by itself or when used as part of
the overall EPB assessment (illustrated in Figure 4 for one module with the double appearance of the circled
number 1). The difference would rather reside in its application. In a particular building (EPB calculation) more
information can be available on the boundary conditions, which can serve as input to the model (e.g. design
operating (departure and return) temperatures of the heat emission system as input for boiler calculations).
For evaluating the product as such (as put on the market, independent of its ultimate application in a specific
building) standard boundary conditions (e.g. considered representative of the stock-wide average) can be used
as input in the same calculation model (e.g. typical design temperatures of emission systems).
1) For instance in Europe, products are regulated on a pan-European level (through the ecodesign directive and
the ecolabelling regulation), but building regulations are on a national or subnational level, which allows – among
many other things – to take account of the local climate.
ISO/TR 52003-2:2017(E)
Key
Triangle calculated assessment
Square measured assessment
Figure 4 — Relation between the assessment methods and the uses of the indicators
8 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
7  Energy performance features and their indicators
7.1  General
No additional information beyond the accompanying document.
7.2  Normalization to building size
An overall and partial energy performance can be normalized to the building size, by relating it to one
or more of the relevant metrics for the building size, such as volume or floor area.
This subject is dealt with in ISO 52000-1 and the accompanying document, ISO/TR 52000-2, but the
choices can have a strong influence on the numeric value of the energy performance and of the energy
performance requirements.
The reference floor area is one of the options for the reference size of the building. Some countries use
another measure for the size, e.g. the space volume. These choices are facilitated in ISO 52000-1:2017,
Annex A.
A factor with a strong influence is the choice which categories of spaces are included in the reference
size of the building. If spaces are included in the reference size which have a relatively low energy use
due to low indoor environment requirements (for instance no heating or cooling, only lighting and
ventilation requirements, as can be typical for underground parking garages), then the average energy
use per floor area (or per volume) will be more favourable, and vice versa. ISO/TR 52000-2 gives more
detailed considerations and examples.
Some countries have indicated that they use a weighting factor for the contribution of the size of specific
space categories to the reference size. In order to allow for this approach, the necessary flexibility has
been incorporated into ISO 52000-1.
The type of dimension used has also a large impact on the specific value obtained after normalization.
For a house of 10 m × 10 m, the indicator obtained using internal dimensions could be 20 % larger than
the one obtained with external dimensions.
7.3  Energy performances and their indicators
7.3.1  Overall energy performances
No additional information beyond the accompanying document.
7.3.2  Partial energy performances
No additional information beyond the accompanying document.
7.4  Ratios of identical/similar quantities as indicators for energy performances
Some practical considerations with respect to ratios are:
— A ratio of identical quantities can be communicated succinctly by putting a letter in front of it (e.g. E
from energy, for primary energy), for instance E73.
— A ratio can sometimes take negative values, e.g. when the exported energy exceeds the delivered
energy (or at least the part of the delivered energy that is considered in the EPB calculations). This
can for instance be the case for the renewable energy ratio (see ISO 52000-1:2017, 9.7).
— For uniformity of communication, the ratio is typically rounded to 2 significant figures. Such fine
subdivision still maintains a quasi-continuous scale.
ISO/TR 52003-2:2017(E)
— Without scaling factor, the ratio typically hovers in the range between 0 and 1 (or more than 1, if the
denominator is quite “strict”). By using a scaling factor of e.g. 100, the figure can be rounded to the
nearest integer value so that no digital separator is needed. This facilitates communication.
— Because this can differ from indicator to indicator, it is important to clearly communicate what is
good and bad (e.g. the lower the value, the better, i.e. a lower value is a better performance).
— A further judgment can be communicated by setting benchmarks and references, and possibly
further associating (multi-coloured, e.g. green to red) labels to the scale e.g. from A (or A+++) to G:
see also Annex E.
NOTE If it is desired to have a reverse scale (e.g. the higher, the better instead of vice-versa), this can be
achieved by taking the negative of the ratio and adding an appropriate constant (c). The new definition then
becomes:
I= c- f* X/ X
ref
Some advantages of a ratio are:
— Single numeric value (which is easy for communication) while differentiated: each particular
building has its appropriate, tailored indicator.
— The ratio is immediately a quality indicator: lower (or higher, depending on the type of indicator)
values indicate how much better a given building performs compared to the reference.
— Since standardized energy calculations usually do not exactly correspond to the real energy
consumption, the dimensionless number fully focuses on the regulatory purpose, namely to
differentiate among different energy efficient designs (and to impose a requirement when applicable).
A drawback of a ratio is:
— In order to maintain an adequate indicator in the future, the reference could need to change over
time when the relative cost effectiveness of different technologies changes.
8  Tailoring for requirements and for ratings
8.1  Two approaches
Because the notional reference building approach and the formula approach are so different in their
way of proceeding, it is often spontaneously assumed that the resulting requirements are very different
too. However, despite the methodological differences this does not at all need to be the case, if the same
reference set of hypotheses is taken as starting point for both approaches. This is further explained here.
Figure 5 a) and 5 b) show the information flow of both approaches in a schematic manner. The part of
the figures above the dotted line is the development of the method; the part below the dotted line is its
application in each specific project.
Development of the method
The (explicit or implicit) starting points are in both instances normally identical: the EPB assessment
method and a reference set of technological and geometrical assumptions.
10 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
(a) Notional reference building approach (b) Formula approach
Figure 5 — Schematic of (a) the notional reference building and (b) formula approach
Notional reference building approach
Here, the development work is limited to the judicious choice and detailed, clear description of the set
of reference hypotheses. This then needs to be correctly programmed (for all possible –possibly very
diverse– projects) in the EPB calculation tool.
Formula approach
Here, the EPB assessment method and the set of reference hypotheses are used to derive a generic
formula (which usually is relatively simple). In practice, 2 ways to derive the formula appear to be used
(often in a combined and/or complementary manner), as shown in Figure 5 b):
— The analytical way seems most easily applied in the case of monthly or seasonal methods. Application
to hourly methods can prove quite difficult. In this instance, all the hypotheses are introduced in
the equations of the EPB assessment method. Only the few input values of the method related to the
specific project then remain. Additionally, some approximations are made: for instance, the value
of the utilization factors is determined for a typical building (or as the average calculated for many
buildings, covering the application range) and is then used as a fixed value in the remainder of the
equations. The final outcome is usually double-checked with full, detailed calculations (also using
the reference hypotheses) on a sufficient number of building geometries.
— In the statistical way, a sufficiently large number (e.g. a few 100) of (preferably real, rather than
fictitious) building geometries are considered. This collection should include extreme cases, such
as very small and very large sizes, very small and very large envelope to floor area ratios, etc.
For each geometry the requirement is calculated with the EPB assessment method and the set of
reference hypotheses. The resulting set of outputs is used to determine the numeric parameters of a
generic formula that has the specific project features as input. The general form of the formula (e.g.
linear or non-linear dependence on each of the variables) needs careful consideration, and can be
based on (rougher) analytical deduction as in the previous case, but this time without quantitative
ISO/TR 52003-2:2017(E)
calculation. For complex formulae (as can for instance be needed in non-residential buildings) fully
automated curve fitting could not lead to satisfactory results, and smarter (e.g. step by step), semi-
manual curve fittings could be needed.
As indicated, in practice both ways thus are not strictly separated, but are to a greater or lesser extent
combined.
Usually, the result is actually a set of different formulas, each of which applicable to a specific
combination of circumstances, such as:
— for different building categories (dwelling, office, etc.);
— for certain ranges (e.g. as a function of size) within a given category (e.g. because the assessment
method uses different hypotheses over different ranges); and
— for different climates.
Application of the method
The results of the development process are now combined with a few real characteristics (building size,
thermal envelope area, etc.) of the specific project for which the requirement needs to be determined.
Notional reference building approach
As shown in Figure 5 a), the project characteristics are directly combined with the set of reference
hypotheses in a full EPB calculation, which is rerun for every individual project, and for every input
change of the project features that are used as input. The number of calculations in the programme is
thus doubled: for every change of the input, both the actual energy performance and the requirement or
reference are recalculated.
Formula approach
The formula that has been developed (see 8.1) is used to calculate with the specific project features as
input in a very rapid manner the requirement or reference.
Discussion
In essence, the formula is a condensed form of (and replaces) the full EPB calculation. This substitution
is possible because the set of reference hypotheses is fixed and freezes most of the input variables of the
assessment method.
When the starting points are exactly identical (notably the full set of reference hypotheses), then the
requirements/rating references that result from the notional reference building approach on the one
hand and the formula approach on the other hand are normally (almost) equal (in as far as the formula
developed is adequate, i.e. not too simplistic). So, although the intermediate approach is different,
identical starting points lead to roughly identical final results. This is corroborated by empirical
experience.
NOTE When the requirement is expressed as a ratio (see Clause 7), the result of the notional reference
building or formula calculation is rather used as denominator in the ratio, and the requirement is then a fixed
value, e.g. 0,7, or 1, or 100 (depending on the definition of the ratio). Such single, fixed number can facilitate
communication.
8.2  Project characteristics for tailoring
No additional information beyond the accompanying document.
12 © ISO 2017 – All rights reserved

ISO/TR 52003-2:2017(E)
9 Energy performance requirements
9.1  General
NOT
...