ISO/TR 52018-2:2017
(Main)Energy performance of buildings — Indicators for partial EPB requirements related to thermal energy balance and fabric features — Part 2: Explanation and justification of ISO 52018-1
Energy performance of buildings — Indicators for partial EPB requirements related to thermal energy balance and fabric features — Part 2: Explanation and justification of ISO 52018-1
ISO/TR 52018-2:2017 refers to ISO 52018‑1. ISO 52018‑1 gives a succinct enumeration of possible requirements related to thermal energy balance features and to fabric features. It also provides tables for regulators to report their choices in a uniform manner. ISO/TR 52018-2:2017 provides many background considerations that can help both private actors and public authorities, and all stakeholders involved, to take informed decisions. ISO/TR 52018-2:2017 does not contain any normative provision.
Performance énergétique des bâtiments — Indicateurs pour des exigences PEB partielles liées aux caractéristiques du bilan énergétique thermique et du bâti — Partie 2: Explication et justification de l’ISO 52018-1
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Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 52018-2
First edition
2017-06
Energy performance of buildings —
Indicators for partial EPB
requirements related to thermal
energy balance and fabric features —
Part 2:
Explanation and justification of ISO
52018-1
Performance énergétique des bâtiments — Indicateurs pour
des exigences PEB partielles liées aux caractéristiques du bilan
énergétique thermique et du bâti —
Partie 2: Explication et justification de l’ISO 52018-1
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and subscripts . 1
5 General aspects . 2
6 Mix of EPB features with requirements . 3
7 Summer thermal comfort . 3
7.1 Motivation . 3
7.2 Points of attention . 3
7.3 Indicators . 5
7.4 Comparable economic strictness . 5
7.5 New construction/renovation . 6
7.6 Exceptions . 6
8 Winter thermal comfort . 6
9 Energy need for heating, or variants . 6
9.1 Motivation . 6
9.2 Indicators . 7
9.3 Comparable economic strictness . 8
9.4 New construction/renovation . 9
9.5 Exceptions . 9
10 Energy need for cooling, or variants . 9
11 Combination of “needs” . 9
12 Overall thermal insulation of the thermal envelope .10
12.1 Motivation .10
12.2 Indicators .10
12.3 Comparable economic strictness .10
12.4 New construction/renovation .11
12.5 Intermediate forms between overall and individual thermal insulation .11
13 Thermal insulation of individual elements of the thermal envelope .11
13.1 Motivation .11
13.2 Indicators .12
13.3 Points of attention .12
13.4 Comparable economic strictness .14
13.5 New construction/renovation .14
13.6 Exceptions .15
14 Thermal bridges .15
14.1 General .15
14.2 Motivation .15
14.3 Requirement setting .15
14.4 Alternative routes .16
14.5 New construction/renovation .17
14.6 Further information .18
15 Window energy performance .18
15.1 Motivation .18
15.2 Indicators .18
15.3 Points of attention .18
15.4 New construction/renovation .18
16 Airtightness.19
16.1 Motivation .19
16.2 Indicator and comparable economic strictness .19
16.3 New construction/renovation .20
16.4 Measurement .20
16.5 Further information .21
17 Solar control .22
Annex A (informative) Input and method selection data sheet — Template.23
Annex B (informative) Input and method selection data sheet — Default choices .24
Annex C (informative) Regional references in line with ISO Global Relevance Policy .26
Annex D (informative) Example method for integrating fictitious cooling into the overall
EPB indicators .27
Annex E (informative) Illustration of the variable value of the heating need per useful floor
area for a given set of technical measures .29
Annex F (informative) An underpinning of an expression for the maximum mean
thermal transmittance .33
Bibliography .37
iv © ISO 2017 – All rights reserved
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/d irectives).
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/p atents).
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 the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: ww w .iso. org/iso / foreword. html.
ISO/TR 52018-2 was prepared by ISO technical committee ISO/TC 163, Thermal performance and
energy use in the built environment, Subcommittee SC 2, Calculation methods, in collaboration 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 52018 series can be found on the ISO website.
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 52018-1. Essential information provided in Part 1 is not repeated in this part.
References to a clause refer to the combined content of that clause in both parts 1 and 2. Brief articles
[20] [21] [22]
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,
[1]
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-
[2]
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
[3]
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.
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
[2]
contents (see CEN/TS 16629 ):
— to avoid flooding and confusing the actual normative part with informative content,
vi © ISO 2017 – All rights reserved
— to reduce the page count of the actual standard, and
— to facilitate understanding of the set of EPB standards.
[17]
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 52018-1, which forms part of the set EPB standards.
The role and the positioning of the accompanied standard in the set of EPB standards is defined in the
Introduction to ISO 52018-1.
General aspects of EPB indicators, requirements, ratings and certificates and application to the overall
[5] [6]
energy performance of buildings can be found in ISO 52003-1 and ISO/TR 52003-2 .
Accompanying spreadsheet
Because in the accompanying document ISO 52018-1 no calculation procedures are defined, an
accompanying calculation spreadsheet is not relevant.
TECHNICAL REPORT ISO/TR 52018-2:2017(E)
Energy performance of buildings — Indicators for partial
EPB requirements related to thermal energy balance and
fabric features —
Part 2:
Explanation and justification of ISO 52018-1
1 Scope
This document refers to ISO 52018-1.
ISO 52018-1 gives a succinct enumeration of possible requirements related to thermal energy balance
features and to fabric features. It also provides tables for regulators to report their choices in a uniform
manner. This document provides many background considerations that can help both private actors
and public authorities, and all stakeholders involved, to take informed decisions.
This document does not contain any normative provision.
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.
ISO 52018-1, Energy performance of buildings – Indicators for partial EPB requirements related to thermal
energy balance and fabric features – Part 1: Overview of options
NOTE More information on the use of EPB module numbers, in all EPB standards, for normative references
to other EPB standards is given in ISO/TR 52000-2.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 52018-1 apply.
[4]
More information on some key EPB terms and definitions is given in ISO/TR 52000-2 .
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
4 Symbols and subscripts
For the purposes of this document, the symbols and subscripts given in ISO 52018-1 apply.
[4]
More information on key EPB symbols and subscripts is given in ISO/TR 52000-2 .
5 General aspects
This document is fully complementary to ISO 52018-1. For a good comprehension, before reading
a clause in this document, the corresponding (succinct) clause in ISO 52018-1 should be read, as this
document does not repeat the content of ISO 52018-1, but only provides additional information.
This document contains many straightforward considerations with which many readers may already be
familiar. In order for the text to also provide full support to novices in the field, such basic considerations
have nevertheless been included. On the other hand, commonly circulating argumentations that could
not withstand the test of critical, rational analysis have been omitted. It is self-evident, by the very
nature of the topic, that the treatment can never be fully exhaustive; many additional motivations, for
instance influenced by specific local conditions, may influence the final choice of the mix of energy
features and indicators for which requirements are set.
For each of the partial EPB features enumerated in ISO 52018-1, this document formulates background
considerations with respect to the following aspects (in as far as applicable):
— possible motivations,
— possible indicators,
— comparable economic strictness of the requirements,
— practical points of attention,
— testing,
— new construction and renovation issues,
— exceptions,
— other.
Achieving a good indoor environmental quality is one of the major objectives when designing buildings
(first and foremost for the people in the building, but also for the proper preservation of any –specific–
goods in the building). The topic of indoor environment is thematically and technically closely
related to the energy efficiency of buildings, and both aspects are therefore logically considered in an
integrated manner when building regulations are established. All the partial EPB features discussed
in ISO 52018-1 and in this document are listed in Table 1 together with an indication whether indoor
environment and/or energy efficiency is (are) usually the main motivation(s). (There may of course still
be other possible reasons for setting a requirement, such as fabric preservation, but such other reasons
are not visualized in the summary table.) Requirements on most EPB features may to a greater or lesser
extent serve both purposes. The nuances are further discussed in each of the clauses.
Table 1 — Overview of the different partial EPB features
Clause Partial EPB feature Indoor Energy
environment efficiency
6 summer thermal comfort X (X)
7 winter thermal comfort X (X)
8 energy “need” for heating, or variants (X) X
9 energy “need” for cooling, or variants (X) X
10 combination of “needs” X
11 overall thermal insulation of the envelope X
12 thermal insulation of individual envelope elements X X
13 thermal bridges X X
2 © ISO 2017 – All rights reserved
Table 1 (continued)
Clause Partial EPB feature Indoor Energy
environment efficiency
14 window energy rating X
15 airtightness X X
16 solar control X X
Often, an important consideration when setting EPB requirements is to achieve a strictness that
is more or less cost optimal (at an assumed scenario of the future energy prices) for each individual
[5]
construction project. This issue is explained in a general manner in ISO 52003-1 and ISO/TR 52003-
[6]
2 . In this document, this aspect is discussed in a more practical manner for each of the EPB features.
6 Mix of EPB features with requirements
No additional information beyond ISO 52018-1.
7 Summer thermal comfort
7.1 Motivation
If there are complaints by the building users about the indoor environmental quality, it often includes
summer thermal comfort. The occurrence of this problem can potentially be aggravated by EPB
building regulations if these are not well-considered and well-equilibrated. Partial EPB requirements
only dealing with the heating aspect may lead designer teams to maximize solar gains in winter, while
neglecting the summer impact. And in uncooled buildings, or if active cooling would not be included in
the overall energy performance assessment, even an overall EPB requirement can cause such single-
sided design.
Setting a summer thermal comfort requirement may thus be an important complement in order to
achieve a balanced, integral building design that performs well in all respects, both in winter and in
summer. In addition, good summer indoor conditions strongly reduce the probability that active cooling
will be installed later on during the lifetime of the building. In this manner such requirement thus also
contributes in the long run to the energy saving goal.
7.2 Points of attention
Special consideration should be given to the potential issue that a diverging approach between uncooled
and actively cooled buildings might result in unwanted consequences.
For instance, if overall EPB requirements and/or partial EPB requirements (e.g., on the cooling “need”)
in actively cooled buildings are much more severe than in uncooled buildings, and if at the same
time there is no attention in the building regulation for summer comfort in uncooled buildings, then
the regulation might cause (especially in the segment of the construction market that is first cost
dominated) an increase of uncooled building designs with uncomfortable summer conditions, resulting
in the installation of (potentially less efficient) active cooling any time after construction.
Vice-versa, a requirement on summer thermal comfort in uncooled buildings that is not matched with
(overall and/or partial) EPB requirements that equally impact cooled buildings, might possibly cause
an undesired immediate shift in new construction towards actively cooled buildings for the sole reason
of a regulatory requirement that is technically and/or economically more easily satisfied.
A possible approach to avoid such divergent regulatory treatment between uncooled and cooled
buildings is to simply set for a given building category (such as dwellings, offices, schools, etc.) the
same type of requirement and the same strictness for each building, independently of the fact whether
or not the building is actively cooled. The requirement can either be a cooling “need” requirement
(see Clause 10) for all buildings (so, also in buildings that are not actively cooled) or alternatively a
summer thermal comfort requirement for all buildings (whereby in the evaluation of this requirement,
it is assumed that the conditioning system in actively cooled building is switched off). It goes without
saying that if certain design variables (e.g., operable windows) are treated differently in both features,
the choice for one or the other of both features will or will not stimulate good use of these technical
measures.
NOTE Sometimes, the fear is expressed that setting a cooling “need” requirement also for uncooled
buildings might be perceived (or misconstrued) by some market actors as an implicit regulatory message that
active cooling is the reference. However, experience has shown that clear (and permanent) public communication
surrounding the regulation can avoid this issue. Moreover, the significant extra cost of effectively installing an
active cooling system also constitutes a strong constraint, especially since spare capital is rarely available at the
time of construction.
An alternative way of avoiding any unwanted consequences is to complement a summer thermal
comfort requirement for all uncooled buildings (which is sufficiently strict to be meaningful) with a
1)
(technically and economically equally strict ) cooling need requirement (see Clause 10) for all actively
cooled buildings.
Another possible source of divergent treatment between cooled and uncooled buildings may occur on
the level of the overall EPB requirement. If the quantitative limit to the overall EPB indicator is identical
for both types (i.e., actively cooled and uncooled) of buildings, it will not correspond to the cost optimal
level of energy efficiency measures for each of both types. A carefully differentiated quantitative
limit may solve this issue. Another approach is to have the same quantitative overall EP requirement,
but to include for uncooled buildings a fictitious cooling consumption in the overall EP calculation,
whereby the regulation sets a fixed overall cooling equipment efficiency and a fixed primary energy
factor to convert the calculated cooling need to primary energy. Setting these values slightly more
favourable than the best current technologies, avoids that cooled buildings would more easily satisfy
the overall EP requirement, and thus be stimulated by the regulation (apart from all the other decision
influencing factors, such as higher – first and operational – costs, controlled thermal environment, etc.).
A disadvantage of fictitious cooling is that the relation between the calculated and real consumption
diminishes (also in a principle manner, apart from all the different boundary conditions). In Annex D
a further developed and more nuanced methodology is described that makes use of a conventional
probability of a later installation of active cooling related to the risk of overheating.
A totally different point of attention concerns the zoning. The risk of overheating may vary strongly
from 1 room to another, depending on very many factors, such as the solar gains (there is for instance
often 2 times more glazing in a corner room than in a room of the same size in the middle of the
sidewall of the building) and the internal gains (e.g., due to a strong difference in occupation density,
for instance an individual office versus a cinema hall). Individual evaluation of all (types of) rooms in a
2)
building is usually not considered feasible within the context of a regulation , and (much) larger zones
are typically used for any calculation. The resulting aggregation and intrinsic averaging will of course
fail to reveal local summer comfort problems in specific rooms.
Vice-versa, another potential issue of zoning is related to the unavoidable simplifications of the
modelling and the consequences this may have on the calculation of single rooms or small zones.
EXAMPLE For instance, a room (e.g., a bathroom) in the centre of a dwelling (e.g., an apartment) may have
little or no transmission heat transfer towards the outside, and the transmission transfer towards adjacent
rooms in neighbouring conditioned zones may by convention be considered nil in the EPB modelling. Also the
ventilation heat transfer coefficient of this room by itself may be very small or even zero. A value of the internal
gains that is considered representative for the average of the dwelling as a whole may actually be quite large for
a bathroom, but is nevertheless often imposed by the fixed calculation conventions. When the summer thermal
comfort of the bathroom is then evaluated, such combination of factors in the modelling may cause unrealistic
results and it may even be that a summer requirement (i.e., the maximal value of the summer indicator) is
mathematically impossible to satisfy.
1) Or possibly stricter, if so desired.
2) Also, it would be difficult in a regulatory context to define differentiated internal gains for rooms with the same
function, although this may in practice be one of the causes of local overheating.
4 © ISO 2017 – All rights reserved
When a summer thermal comfort requirement is imposed in the regulation, it may therefore be
preferred to set it for sufficiently large zones. In residential buildings, it might be stipulated that the
requirement always be evaluated for the entire dwelling or building unit (e.g., individual apartment) as
whole, even if for other purposes smaller thermal zones are defined. But, for informative purposes only,
it is of course still easily possible to evaluate (in a fully automated manner) the overheating indicator
for each of the thermal zones apart, which have already been defined for other reasons. It is then up to
the expertise of the programme user (assisted by the manual, help function, automated messages, etc.;
and aided by his/her dedicated training and practical experience) to make a sound judgement whether
a poor summer comfort indicator for a given zone reveals a true, physical problem, or whether it is
caused by the intrinsic restrictions of the modelling (as in the bathroom example above).
7.3 Indicators
Several possible indicators can be considered for the summer thermal comfort.
For monthly calculations, the normalized non-useful gains for heating (which cause overtemperature
above the heating set-point) have been shown to correlate well with the overheating above the thermal
comfort limit.
For hourly calculations, a possible indicator is the number of hours (in h) on an annual basis that the free
floating temperature exceeds a fixed reference temperature. Alternatively, the temperature weighted
time (in Kh) above the fixed reference temperature can be used. The latter is a bit more sophisticated and
increases more rapidly than the former (quadratic versus linear course). The latter thus better reveals
the true extent of any summer discomfort problem and is therefore the preferred indicator. The fixed
temperature that is chosen as reference will logically depend on the climate of the country or region.
NOTE 1 In buildings that satisfy a number of conditions (without active cooling, with operable windows,
no strict dress code, etc.) a certain degree of user adaptation to high summer temperatures can occur.
[7]
ISO 17772-1:2017, A.2 provides a model to evaluate the corresponding comfort level. For the buildings that
fall within the application scope of the model, these calculations will of course give a much better indication of
the summer comfort quality of the building, and are thus to be preferred for tailored design decisions. (But the
important consideration with respect to the dependence of the result on the zoning (see 7.2) needs to be well
kept in mind.).
NOTE 2 Because of its limited application range, the model in ISO 17772-1:2017, A.2 can however not be
used to set a systematic regulatory requirement applicable to all buildings, e.g., to both actively cooled and
uncooled buildings. For purely informative purposes, though, any EPB software could calculate (systematically
and automatically or otherwise only upon request of the programme user) this indicator too. However, some
extra user input might be needed if the aim is a calculation that is fully conform the adaptive comfort model.
Apart from indicating the comfort class (I, II or III), the calculation could also provide a more continuous output,
e.g., the temperature weighted time that the boundaries of class I are exceeded, so as to give finer feedback to
designers on the impact of changing different variables.
7.4 Comparable economic strictness
For energy efficiency measures, a life cycle cost analysis allows to compare initial investments with
all operational expenditures and thus to determine which set of technical measures is cost optimal.
This can be the basis for setting requirements. For indoor environment aspects, such as summer
thermal comfort, such economic analysis is in principle not applicable, as the benefits are difficultly
quantifiable in monetary terms. A partial exception may be labour cost in offices and other workplaces:
the loss of productivity due to thermal discomfort can be estimated (in a more or less rough manner) by
means of (laboratory) experiments, or on the basis of experience, etc. This then in turn again allows a
rudimentary economic optimization of summer comfort investments.
Alternatively, reasonable summer thermal comfort requirements may simply be taken as a starting
point, and it can then be evaluated whether these are affordable in terms of investments. In many
buildings (notably if the internal gains are not too high) judicious choice of window area, glazing type
and orientation are an easy and relatively cheap means to limit overheating.
7.5 New construction/renovation
An overall summer thermal comfort regulatory requirement is most easily imposed in the case of new
construction. For renovation, element level requirements, notably solar control (see Clause 17) usually
prove more practical.
7.6 Exceptions
As illustrated in 7.3 by means of the bathroom example, the combination of the chosen indicator and the
numerical strictness of the requirement should be thoroughly evaluated beforehand on a large sample
of cases, so that a general requirement can be set with confidence. If still needed, rare individual cases
can then still be granted exception on the basis of a general hardship clause in the EPB regulation, cf.
[5]
ISO 52003-1 .
8 Winter thermal comfort
Very similar considerations to those formulated for summer thermal comfort apply, mutatis mutandis,
to winter thermal comfort. They are not repeated here in a rephrased manner, as the required
adaptations are so self-evident that the reader will readily have an appropriate understanding.
It should be noted that due to the more general application of very low energy buildings the geographic
area (seen on a global scale) where active heating (under whatever form) can be completely omitted,
may extend over time.
NOTE It is obvious that, similar to the summer situation, also in winter user adaptation can occur, notably
the use of warmer clothing (thick jumpers, thermal underwear, etc.), as is common in lower income countries
[7] [8]
with moderately cold winters. ISO 17772-1 (or its CEN version EN 16798–1 ), however, provides no model for
that purpose, so that it does not allow for a more detailed assessment.
9 Energy need for heating, or variants
9.1 Motivation
The main motivation to set requirements on the energy “need” for heating is usually related to energy
savings:
— In heating dominated climates, the factors affecting this “need” determine to a large extent the
overall energy consumption of the building. In these regions, setting this partial requirement
thus constitutes an important step towards achieving a good overall energy performance. This
partial requirement is in line with the general philosophy of the “trias energetica” that first seeks
to minimize the demand before looking in a second instance at appropriate and efficient heating
systems, possibly making use of renewable energy.
— This heating “need” relates to a large extent or – potentially even fully, depending on its exact
definition; see below– to the building fabric, i.e., the building as such, without technical systems.
As it is, generally speaking, practically difficult and financially expensive to improve the energy
performance of the fabric after initial construction, this partial requirement ensures that a basic
energy performance will likely be achieved throughout the lifetime of the building. It counteracts
the risk that an overall EPB requirement is initially primarily achieved with very advanced technical
systems, but which are later – at the time of their replacement – substituted for by lower performance
equipment, thus deteriorating the initial overall energy performance. Like other partial, fabric-
related requirements (see following clauses), the heating “need” requirement thus ensures a certain
degree of robustness of the overall energy efficient design.
— When the overall energy performance is expressed in another quantity than energy, e.g., in terms
of CO emissions, then a heating “need” requirement ensures that also the energy demand is kept
moderate, even if low-CO heating carriers are used.
6 © ISO 2017 – All rights reserved
A secondary objective of setting a heating “need” requirement may also be to guarantee to a certain
extent a good indoor environmental quality in winter, as the “need” requirement requires due attention
to the fabric and the ventilation provisions.
If no heating system is present, a requirement on the heating “need” (which is then fictitious) can still be
imposed so as to ensure in an indirect manner reasonable thermal comfort in winter and thus to limit
the probability that space heating is installed later on (e.g., in the form of electric resistance heating,
which is relatively simple to install). And if space heating is nevertheless installed afterwards, such
requirement ensures that its consumption will remain checked.
NOTE Such heating “need” requirement in the absence of a heating system constitutes a surrogate
alternative to setting a requirement on the degree of thermal discomfort during the winter season under free
floating temperature conditions, see Clause 8.
9.2 Indicators
The total annual heating need (as sum of the need for the heating of the spaces and the need for the
active preheating of hygienic ventilation air, see ISO 52018-1:2017, Clause 9) can be used as an indicator.
This includes the effect of the actual ventilation system that is (being) implemented in the project, and
energy efficient ventilation choices are thus stimulated.
Often however, a modified indicator is adopted for setting the partial EP
...
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