SIST EN ISO 10077-2:2017

SLOVENSKI STANDARD
01-september-2017
1DGRPHãþD
SIST EN ISO 10077-2:2012
SIST EN ISO 10077-2:2012/AC:2012
7RSORWQH]QDþLOQRVWLRNHQYUDWLQSRONHQ,]UDþXQWRSORWQHSUHKRGQRVWLGHO
5DþXQVNDPHWRGD]DRNYLUMH,62
Thermal performance of windows, doors and shutters - Calculation of thermal
transmittance - Part 2: Numerical method for frames (ISO 10077-2:2017)
Wärmetechnisches Verhalten von Fenstern, Türen und Abschlüssen - Berechnung des
Wärmedurchgangskoeffizienten - Teil 2: Numerisches Verfahren für Rahmen (ISO 10077
-2:2017)
Performance thermique des fenêtres, portes et fermetures - Calcul du coefficient de
transmission thermique - Partie 2 : Méthode numérique pour les encadrementes (ISO
10077-2:2017)
Ta slovenski standard je istoveten z: EN ISO 10077-2:2017
ICS:
91.060.50 Vrata in okna Doors and windows
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 10077-2
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2017
EUROPÄISCHE NORM
ICS 91.060.50; 91.120.10 Supersedes EN ISO 10077-2:2012
English Version
Thermal performance of windows, doors and shutters -
Calculation of thermal transmittance - Part 2: Numerical
method for frames (ISO 10077-2:2017)
Performance thermique des fenêtres, portes et Wärmetechnisches Verhalten von Fenstern, Türen und
fermetures - Calcul du coefficient de transmission Abschlüssen - Berechnung des
thermique - Partie 2 : Méthode numérique pour les Wärmedurchgangskoeffizienten - Teil 2: Numerisches
encadrementes (ISO 10077-2:2017) Verfahren für Rahmen (ISO 10077-2:2017)
This European Standard was approved by CEN on 27 February 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10077-2:2017 E
worldwide for CEN national Members.

EN ISO 10777-2:2017 (E)
Contents Page
European foreword . 3

EN ISO 10777-2:2017 (E)
European foreword
This document (EN ISO 10777-2:2017) has been prepared by Technical Committee CEN/TC 89
“Thermal performance of buildings and building components”, the secretariat of which is held by SIS, in
collaboration with Technical Committee ISO/TC 163 "Thermal performance and energy use in the built
environment".
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2018 and conflicting national standards shall
be withdrawn at the latest by January 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
This document is part of the set of standards on the energy performance of buildings (the set of EPB
standards) and has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association (Mandate M/480, see reference [EF1] below), and supports essential
requirements of EU Directive 2010/31/EC on the energy performance of buildings (EPBD, [EF2]).
In case this standard is used in the context of national or regional legal requirements, mandatory
choices may be given at national or regional level for such specific applications, in particular for the
application within the context of EU Directives transposed into national legal requirements.
Further target groups are users of the voluntary common European Union certification scheme for the
energy performance of non-residential buildings (EPBD art.11.9) and any other regional (e.g. Pan
European) parties wanting to motivate their assumptions by classifying the building energy
performance for a dedicated building stock.
This document supersedes EN ISO 10077-2:2012.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands,
Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
the United Kingdom.
References:
[EF1] Mandate M480, Mandate to CEN, CENELEC and ETSI for the elaboration and adoption of
standards for a methodology calculating the integrated energy performance of buildings and
promoting the energy efficiency of buildings, in accordance with the terms set in the recast of the
Directive on the energy performance of buildings (2010/31/EU) of 14th December 2010
EN ISO 10777-2:2017 (E)
th
[EF2] EPBD, Recast of the Directive on the energy performance of buildings (2010/31/EU) of 14
December 2010
Endorsement notice
The text of ISO 10777-2:2017 has been approved by CEN as EN ISO 10777-2:2017 without any
modification.
INTERNATIONAL ISO
STANDARD 10077-2
Third edition
2017-06
Thermal performance of windows,
doors and shutters — Calculation of
thermal transmittance —
Part 2:
Numerical method for frames
Performance thermique des fenêtres, portes et fermetures — Calcul
du coefficient de transmission thermique —
Partie 2: Méthode numérique pour les encadrements
Reference number
ISO 10077-2:2017(E)
©
ISO 2017
ISO 10077-2:2017(E)
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and subscripts . 2
4.1 Symbols . 2
4.2 Subscripts . 3
5 Calculation method . 3
5.1 Output of the method . 3
5.2 General principle . 3
5.3 Validation of the calculation programs . 4
6 Calculation of thermal transmittance . 4
6.1 Output data . 4
6.2 Calculation time intervals . 4
6.3 Input data . 4
6.3.1 Geometrical characteristics . 4
6.3.2 Thermal conductivity values . 5
6.3.3 Emissivity of surfaces . 6
6.3.4 General boundaries . 6
6.3.5 Boundaries for roller shutter boxes . 6
6.4 Calculation procedures . 7
6.4.1 Determination of thermal transmittance . 7
6.4.2 Treatment of cavities using the radiosity method . 8
6.4.3 Treatment of cavities using the single equivalent thermal conductivity method 18
7 Report .24
7.1 Contents of report .24
7.2 Geometrical data .24
7.3 Thermal data . .25
7.3.1 Thermal conductivity . .25
7.3.2 Emissivity .25
7.3.3 Boundary conditions .25
7.4 Presentation of results .25
Annex A (normative) Input and method selection data sheet — Template .26
Annex B (informative) Input and method selection data sheet — Default choices .28
Annex C (normative) Regional references in line with ISO Global Relevance Policy .30
Annex D (normative) Thermal conductivity and other characteristics of selected materials .31
Annex E (normative) Surface resistances .34
Annex F (normative) Determination of the thermal transmittance .36
Annex G (normative) General examples for the validation of calculation programs using the
radiosity method for the treatment of cavities .40
Annex H (normative) Examples of window frames for the validation of calculation
programs using the radiosity method for the treatment of cavities .45
Annex I (normative) Examples of window frames for the validation of calculation programs
using the single equivalent thermal conductivity method for the treatment of cavities .57
Annex J (normative) Wood species listed in Annex D .68
ISO 10077-2:2017(E)
Bibliography .70
iv © ISO 2017 – All rights reserved

ISO 10077-2:2017(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 the
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.
ISO 10077-2 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 89, Thermal performance of buildings and building components, in collaboration with ISO
Technical Committee ISO/TC 163, Thermal performance and energy use in the built environment,
Subcommittee SC 2, Calculation methods, in accordance with the agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 10077-2:2012), which has been
technically revised to comply with the requirements for the EPB set of standards. It also incorporates
the Technical Corrigendum ISO 10077-2:2012/Cor 1:2012.
In addition, Clause 6 has been technically revised by
— adding a new approach for the treatment of cavities,
— separating conduction/convection and radiation, and
— introducing the radiosity method.
Annex H and Annex G were also added.
A list of all parts in the ISO 10077 series can be found on the ISO website.
ISO 10077-2:2017(E)
Introduction
This document is part of a series aimed at the international harmonization of the methodology for
assessing the energy performance of buildings. Throughout, this series is referred to as a “set of EPB
standards”.
All EPB standards follow specific rules to ensure overall consistency, unambiguity and transparency.
All EPB standards provide a certain flexibility with regard to the methods, the required input data and
references to other EPB standards, by the introduction of a normative template in Annex A and Annex B
with informative default choices.
For the correct use of this document, a normative template is given in Annex A to specify these choices.
Informative default choices are provided in Annex B.
The main target groups for this document are architects, engineers and regulators.
Use by or for regulators: In case ISO 52000-1 is used in the context of national or regional legal
requirements, mandatory choices may be given at national or regional level for such specific
applications. These choices (either the informative default choices from Annex B or choices adapted to
national/regional needs, but in any case following the template of this Annex A) can be made available
as national annex or as separate (e.g. legal) document (national data sheet).
NOTE 1 So in this case:
— the regulators will specify the choices;
— the individual user will apply the document to assess the energy performance of a building, and thereby use
the choices made by the regulators
Topics addressed in this document can be subject to public regulation. Public regulation on the same
topics can override the default values in Annex B of this document. Public regulation on the same topics
can even, for certain applications, override the use of this document. Legal requirements and choices
are in general not published in standards but in legal documents. In order to avoid double publications
and difficult updating of double documents, a national annex may refer to the legal texts where national
choices have been made by public authorities. Different national annexes or national data sheets are
possible, for different applications.
It is expected, if the default values, choices and references to other EPB standards in Annex B are not
followed due to national regulations, policy or traditions, that:
— national or regional authorities prepare data sheets containing the choices and national or regional
values, according to the model in Annex A. In this case a national annex (e.g. NA) is recommended,
containing a reference to these data sheets;;
— or, by default, the national standards body will consider the possibility to add or include a national
annex in agreement with the template of Annex A, in accordance to the legal documents that give
national or regional values and choices.
Further target groups are parties wanting to motivate their assumptions by classifying the building
energy performance for a dedicated building stock.
More information is provided in the Technical Report (ISO/TR 52022-2) accompanying this document.
The framework for overall EPB includes:
a) common terms, definitions and symbols;
b) building and assessment boundaries;
c) building partitioning into space categories;
vi © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
d) methodology for calculating the EPB (formulae on energy used, delivered, produced and/or
exported at the building site and nearby);
e) a set of overall formulae and input-output relations, linking the various elements relevant for the
assessment of the overall EPB;
f) general requirements for EPB dealing with partial calculations;
g) rules for the combination of different spaces into zones;
h) performance indicators;
i) methodology for measured energy performance assessment.
ISO 10077 consists of two parts. This document is intended to provide calculated values of the thermal
characteristics of frame profiles, suitable for use as input data in the calculation method of the thermal
transmittance of windows, doors and shutters given in ISO 10077-1. It is an alternative to the hot box
test method specified in EN 12412–2. In some cases, the hot box method can be preferred, especially if
physical and geometrical data are not available or if the profile is of complicated geometrical shape.
Although the method in this document basically applies to vertical frame profiles, it is an acceptable
approximation for horizontal frame profiles (e.g. sill and head sections) and for products used in sloped
positions (e.g. roof windows). For calculations made with the glazing units in place, the heat flow
pattern and the temperature field within the frame are useful by-products of this calculation.
The ISO 10077 series does not cover building facades and curtain walling, which are covered in
ISO 12631.
Table 1 shows the relative position of this document within the set of EPB standards in the context of
the modular structure as set out in ISO 52000-1.
NOTE 2 In ISO/TR 52000-2, the same table can be found, with, for each module, the numbers of the relevant
EPB standards and accompanying technical reports that are published or in preparation.
NOTE 3 The modules represent EPB standards, although one EPB standard could cover more than one module
and one module could be covered by more than one EPB standard, for instance, a simplified and a detailed method
respectively.
ISO 10077-2:2017(E)
Table 1 — Position of this document (in casu M2–5), within the modular structure of the set of
EPB standards
Building
Overarching Technical building systems
(as such)
Buil
De Do ding
Hu
hu mes auto
Sub Ven mi PV,
Descrip Descrip Descrip Hea Coo mi tic Ligh ma
mo tila difi wind,
tions tions tions ting ling difi hot ting tion
dule tion ca .
ca wat and
tion
tion er cont
rol
sub1 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11
1 General General General
Common
terms and
definitions, Building
a
2 Needs
symbols, energy needs
units and
subscripts
(Free) Indoor
Maximum
conditions
3 Applications load and
without
power
systems
Ways to Ways to Ways to
express express express
energy energy energy
performance performance performance
Building
categories Heat transfer
ISO Emission
5 and by transmis-
10077-2 and control
building sion
boundaries
Heat transfer
Building
by infiltra-
occupancy Distribution
6 tion
operating and control
and ventila-
conditions
tion
Aggregation
of
energy ser- Internal Storage
vices heat gains and control
and energy
carriers
Building Solar Generation
zoning heat gains and control
Load
Building
Calculated dispatching
dynamics
9 energy and
(thermal
performance operating
mass)
conditions
a
The shaded modules are not applicable.
viii © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
Table 1 (continued)
Building
Overarching Technical building systems
(as such)
Buil
De Do ding
Hu
hu mes auto
Sub Ven mi PV,
Descrip Descrip Descrip Hea Coo mi tic Ligh ma
mo tila difi wind,
tions tions tions ting ling difi hot ting tion
dule tion ca .
ca wat and
tion
tion er cont
rol
sub1 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11
Measured Measured Measured
10 energy energy energy
performance performance performance
11 Inspection Inspection Inspection
Ways to
express
12 BMS
indoor com-
fort
External
13 environment
conditions
Economic
calculation
a
The shaded modules are not applicable.
INTERNATIONAL STANDARD ISO 10077-2:2017(E)
Thermal performance of windows, doors and shutters —
Calculation of thermal transmittance —
Part 2:
Numerical method for frames
1 Scope
This document specifies a method and gives reference input data for the calculation of the thermal
transmittance of frame profiles and of the linear thermal transmittance of their junction with glazing
or opaque panels.
The method can also be used to evaluate the thermal resistance of shutter profiles and the thermal
characteristics of roller shutter boxes and similar components (e.g. blinds).
This document also gives criteria for the validation of numerical methods used for the calculation.
This document does not include effects of solar radiation, heat transfer caused by air leakage or three-
dimensional heat transfer such as pinpoint metallic connections. Thermal bridge effects between the
frame and the building structure are not included.
NOTE Table 1 in the Introduction shows the relative position of this document within the set of EPB
standards in the context of the modular structure as set out in ISO 52000-1.
2 Normative references
The following documents are referred to in 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 7345, Thermal insulation — Physical quantities and definitions
ISO 10211, Thermal bridges in building construction — Heat flows and surface temperatures — Detailed
calculations
ISO 10292, Glass in building — Calculation of steady-state U values (thermal transmittance) of multiple
glazing
ISO 10456:2007, Building materials and products — Hygrothermal properties — Tabulated design values
and procedures for determining declared and design thermal values
ISO 12567-2:2005, Thermal performance of windows and doors — Determination of thermal transmittance
by hot box method — Part 2: Roof windows and other projecting windows
ISO 17025, General requirements for the competence of testing and calibration laboratories
ISO 52000-1, Energy performance of buildings — Overarching EPB assessment —– Part 1: General
framework and procedures
EN 673, Glass in building — Calculation of thermal transmittance (U-value) — Calculation Method
EN 12519, Windows and pedestrian doors — Terminology
ISO 10077-2:2017(E)
NOTE Default references to EPB standards other than ISO 52000-1 are identified by the EPB module code
number and given in Annex A (normative template in Table A.1) and Annex B (informative default choice in
Table B.1).
EXAMPLE EPB module code number: M5–5, or M5–5.1 (if module M5–5 is subdivided), or M5–5/1 (if
reference to a specific clause of the standard covering M5–5).
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7345, EN 12519, ISO 52000-1
and the following 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
3.1
EPB standard
[10]
standard that complies with the requirements given in ISO 52000-1, CEN/TS 16628 and
[11]
CEN/TS 16629
Note 1 to entry: These three basic EPB documents were developed under a mandate given to CEN by the European
Commission and the European Free Trade Association (Mandate M/480), and support essential requirements of
EU Directive 2010/31/EU on the energy performance of buildings (EPBD). Several EPB standards and related
documents are developed or revised under the same mandate.
[SOURCE: ISO 52000-1:2017, definition 3.5.14]
4 Symbols and subscripts
4.1 Symbols
For the purposes of this document, the symbols given in ISO 52000-1 and the following apply.
Symbol Name of quantity Unit
A area m
b width, i.e. perpendicular to the direction of heat flow m
d depth, i.e. parallel to the direction of heat flow m
2 4/3
C constant in formula for Nusselt number W/(m ·K )
E intersurface emittance —
F view factor —
h heat transfer coefficient W/(m ·K)
2D
L two-dimensional thermal conductance or thermal W/(m·K)
coupling coefficient
l length m
Nu Nusselt number —
q density of heat flow rate W/m
R thermal resistance m ·K/W
r distance m
T thermodynamic temperature K
U thermal transmittance W/(m ·K)
2 4
σ Stefan-Boltzmann constant W/(m ·K )
2 © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
Symbol Name of quantity Unit
ε emissivity —
λ thermal conductivity W/(m·K)
Ψ linear thermal transmittance W/(m·K)
Θ temperature °C
4.2 Subscripts
For the purposes of this document, the subscripts given in ISO 52000-1 and the following apply.
Subscript Description
c convective (surface to surface)
e external (outdoor)
g glazing
eq equivalent
f frame
fr frame adjacent to roller shutter box
i internal (indoor)
rb radiation black body
m mean
p panel
r radiative
s space (air or gas space)
sb shutter box
se external surface
si internal surface
5 Calculation method
5.1 Output of the method
The possible outputs of this document are the following:
— thermal transmittance of a frame profile, U ;
f
— thermal transmittance of a shutter box, U ;
sb
— linear thermal transmittance of a junction of a frame profile with a glazing, Ψ or opaque panel, Ψ .
g p
5.2 General principle
The calculation is carried out using a two-dimensional numerical method conforming to ISO 10211.
The elements shall be divided such that any further division does not change the calculated result
significantly. ISO 10211 gives criteria for judging whether sufficient sub-divisions have been used.
Two different approaches for the calculation of the heat transfer through cavities are given:
a) radiosity method;
b) single equivalent thermal conductivity method.
ISO 10077-2:2017(E)
The radiosity method considers that the heat transfer through an air cavity occurs simultaneously
through conduction/convection and through radiation. The two phenomena are happening in parallel
so that the calculation of each contribution is done separately.
When using the single equivalent thermal conductivity method the heat flow rate in cavities is
represented by a single equivalent thermal conductivity, λ . This equivalent thermal conductivity
eq
includes the heat flow by conduction, by convection and by radiation, and depends on the geometry of
the cavity and on the adjacent materials.
NOTE The single equivalent thermal conductivity method is equal to the calculation method given in
ISO 10077-2:2012.
Vertical orientation of frame sections and air cavities is assumed for calculations by this document
for the purposes of assigning equivalent thermal conductivity values (see 6.4.2.3.2 and 6.4.3.4.2). This
applies irrespective of the intended orientation of the actual window, including roof windows.
Throughout this document, where indicated in the text, Table C.1 shall be used to identify alternative
regional references in line with ISO Global Relevance Policy.
5.3 Validation of the calculation programs
To ensure the suitability of the calculation program used, calculations shall be carried out on the
examples described in Annexes G and H (using the radiosity method) or Annex I (using the single
equivalent thermal conductivity).
The requirements for all validation cases in Annexes G and H or Annex I shall be fulfilled.
2D
The calculated two-dimensional thermal conductance L for the cases in Annex H or Annex I shall not
differ from the corresponding values given in Tables H.3 and H.4 or Tables I.3 and I.4 by more than ±3 %.
This will lead to an accuracy of the thermal transmittance, U, and the linear thermal transmittance, Ψ,
of about 5 %.
6 Calculation of thermal transmittance
6.1 Output data
The outputs of this document are transmission heat transfer coefficients as shown in Table 2.
Table 2 — Output data
Destination Validity
Description Symbol Unit Varying
module interval
Thermal transmittance of frame profile U W/(m K) M2–5 >0… 20 No
f
Thermal transmittance of shutter box U W/(m K) M2–5 >0… 20 No
sb
Linear thermal transmittance Ψ W/(m K) M2–5 −20… 20 No
6.2 Calculation time intervals
The calculations described in this document are steady-state and do not have time intervals.
6.3 Input data
6.3.1 Geometrical characteristics
Table 3 shows the necessary geometrical characteristics.
4 © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
Table 3 — Identifiers for geometric characteristics
Description Symbol Unit Range Origin Varying
Geometrical data
Cross section of the frame profile Manufacturer No
Cross section of the shutter box Manufacturer No
Cross section of the junction frame
Manufacturer No
profile and glazing
Cross section of the junction frame
Manufacturer No
profile and panel
For frames with special extensions overlapping the wall or other building elements, such as Z-shaped
profiles, the extensions shall be disregarded as illustrated in Figure 1. This applies to all profiles with
special extensions (e.g. H-shape) where the extensions overlap the wall or other building elements.
Other boundaries shall be treated as defined in Figure 4.

Figure 1 — Treatment of profiles with extensions (Z-shape)
NOTE 1 This approximation is for assessment of thermal transmittance. It is not appropriate for the
assessment of condensation risk.
NOTE 2 The extension of the frame profile is disregarded in the calculation of the thermal transmittance of
the window; see ISO 10077-1.
6.3.2 Thermal conductivity values
For the purpose of this document, thermal conductivity values used for solid materials shall be obtained
according to one of the following:
— Table D.1;
— tabulated values given in ISO 10456;
— product standards;
— technical approvals by a recognized national body;
— measurements according to an appropriate International Standard.
Measurements shall be used only if there is no tabulated data or data according to relevant product
standards or a technical approval. Measurements shall be performed at a mean temperature of 10 °C
using the appropriate method by an institute accredited (as specified in ISO 17025) to carry out
those measurements, on samples that have been conditioned at 23 °C and 50 % RH to constant mass
(change in mass not more than 0,1 % over 24 h). To ensure that the thermal conductivity values are
representative of the material (that is, that the value incorporates likely variability of the material and
the measurement uncertainty), one of the following methods shall be used for obtaining the thermal
conductivity value from measured data used in the calculations:
— the thermal conductivity is the declared value obtained from the measured data (at least three
different samples from different lots representing the usual product variation, with ageing taken
ISO 10077-2:2017(E)
into consideration) according to a statistical evaluation as defined in ISO 10456:2007, Annex C, 90 %
fractile;
— if less than three samples, use the mean value multiplied by a factor of 1,25.
6.3.3 Emissivity of surfaces
The surfaces bounding an air cavity shall have an emissivity of 0,9. Values less than 0,9 may be used
only if taken from Table D.3 or measured in accordance with an appropriate standard by an institute
accredited (as specified in ISO 17025) to carry out those measurements. Where based on measured
values, there shall be at least three samples and the results shall be evaluated according to the statistical
treatment in ISO 10456.
NOTE Metallic surfaces such as aluminium alloy frame, steel reinforcement and other metals/alloys have
lower emissivity. Typical values of the emissivity for metallic surfaces are given in Table D.3.
6.3.4 General boundaries
The external and internal surface resistances depend on the convective and radiative heat transfer
to the external and internal environments. If an external surface is not exposed to normal wind
conditions, the convective part may be reduced in edges or junctions between two surfaces. The surface
resistances for horizontal heat flow are given in Annex E. These values shall be used for calculations by
this document irrespective of the intended orientation of the actual window, including roof windows.
Surface condensation shall be assessed on the basis of the lowest internal surface temperature
calculated using the surface resistances in Annex E.
The cutting plane of the infill and the cutting plane to neighbouring material shall be taken as adiabatic
(see Figure 4 and Annex H).
The reference temperature conditions shall be 20 °C internal and 0 °C external.
6.3.5 Boundaries for roller shutter boxes
Calculation of the thermal transmittance of a roller shutter box shall be done with the following
boundary conditions:
— the top of the roller shutter box: adiabatic;
— at the bottom of the roller shutter box where it adjoins the window frame: adiabatic for a distance
of 60 mm;
— surfaces adjacent to the internal environment: surface resistance of 0,13 m ·K/W;
— surfaces adjacent to the external environment: surface resistance of 0,04 m ·K/W.
The cavity within the roller shutter box shall be treated as (see Figure 2):
— if e + e ≤ 2 mm: unventilated; the equivalent thermal conductivity of an unventilated air cavity is
1 3
calculated according to 6.4.2.3;
NOTE Additional hardware like brushes, gaskets, etc. can be taken into account for the determination
of e and e .
1 3
— if e ≤ 35 mm: slightly ventilated; taking the air temperature within the cavity equal to the external
tot
air temperature but with a surface resistance of 0,30 m ·K/W;
— if e > 35 mm: well-ventilated; taking the air temperature within the cavity equal to the external
tot
air temperature but with a surface resistance of 0,13 m ·K/W.
The relevant height of the roller shutter box, b , used for the calculation is the projected distance
sb
between the upper and lower adiabatic boundary (see Figure 2).
6 © ISO 2017 – All rights reserved

ISO 10077-2:2017(E)
The assessment may be done with insulation on either or both of the boundaries B and C indicated in
Figure 2. If that is the case the thickness and thermal conductivity of the insulation shall be stated in
the calculation report.
Dimensions in millimetres
Key
Boundaries (see Annex E):
A adiabatic boundary b height of the roller shutter box
sb
B external surface resistance e , e widths of air gaps on either side of the shutter were it exits from
1 3
the shutter box
C internal surface resistance
e thickness of the shutter
e e + e + e
tot 1 2 3
l position of the frame
fr
NOTE  The window frame (boundary A) is 60 mm wide but located with respect to the roller shutter box according
to the actual situation.
Figure 2 — Schematic example for the treatment of the boundaries for roller shutter boxes
6.4 Calculation procedures
6.4.1 Determination of thermal transmittance
The thermal transmittance of a frame section shall be determined with the glazing replaced by an
insulating panel according to Annex F, with the external and internal surface resistances taken from
Annex E. The linear thermal transmittance of the interaction of frame and glazing shall be determined
from calculations with the glazing in place and with the glazing replaced by an insulated panel.
NOTE 1 The interaction of the frame and the building structure is considered separately for the building as a
whole. It is not part of the thermal transmittance of the frame section.
NOTE 2 In the case of an overlap between the frame section and part of the wall, the linear thermal
transmittance could be negative.
ISO 10077-2:2017(E)
6.4.2 Treatment of cavities using the radiosity method
6.4.2.1 General
The heat transfer through an air cavity occurs simultaneously through convection and through
radiation. The two phenomena are happening in parallel so that the calculation of each contribution can
be done separately.
The calculation of the convective heat transfer is carried out using an equivalent thermal conductivity
and following the rules of 6.4.2.3.2. Given that the formula for the equivalent thermal conductivity
applies to
...