EN ISO 6946:2007

SLOVENSKI STANDARD
01-junij-2008
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SIST EN ISO 6946:1997
SIST EN ISO 6946:1997/A1:2003
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Building components and building elements - Thermal resistance and thermal
transmittance - Calculation method (ISO 6946:2007)
Bauteile - Wärmedurchlasswiderstand und Wärmedurchgangskoeffizient -
Berechnungsverfahren (ISO 6946:2007)
Composants et parois de bâtiments - Résistance thermique et coefficient de
transmission thermique - Méthode de calcul (ISO 6946:2007)
Ta slovenski standard je istoveten z: EN ISO 6946:2007
ICS:
91.060.01 Stavbni elementi na splošno Elements of buildings in
general
91.120.10 Toplotna izolacija stavb Thermal insulation
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 6946
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2007
ICS 91.060.01; 91.120.10 Supersedes EN ISO 6946:1996
English Version
Building components and building elements - Thermal
resistance and thermal transmittance - Calculation method (ISO
6946:2007)
Composants et parois de bâtiments - Résistance thermique Bauteile - Wärmedurchlasswiderstand und
et coefficient de transmission thermique - Méthode de Wärmedurchgangskoeffizient - Berechnungsverfahren (ISO
calcul (ISO 6946:2007) 6946:2007)
This European Standard was approved by CEN on 7 December 2007.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6946:2007: E
worldwide for CEN national Members.

Contents Page
Foreword.3

Foreword
This document (EN ISO 6946:2007) has been prepared by Technical Committee ISO/TC 163 "Thermal
performance and energy use in the built environment" in collaboration with Technical Committee CEN/TC 89
"Thermal performance of buildings and building components", the secretariat of which is held by SIS.
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 June 2008, and conflicting national standards shall be withdrawn at
the latest by June 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 6946:1996.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 6946:2007 has been approved by CEN as a EN ISO 6946:2007 without any modification.

INTERNATIONAL ISO
STANDARD 6946
Second edition
2007-12-15
Building components and building
elements — Thermal resistance and
thermal transmittance — Calculation
method
Composants et parois de bâtiments — Résistance thermique et
coefficient de transmission thermique — Méthode de calcul

Reference number
ISO 6946:2007(E)
©
ISO 2007
ISO 6946:2007(E)
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ii © ISO 2007 – All rights reserved

ISO 6946:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and units . 1
3.1 Terms and definitions. 1
3.2 Symbols and units. 2
4 Principles. 2
5 Thermal resistances . 3
5.1 Thermal resistance of homogeneous layers . 3
5.2 Surface resistances. 3
5.3 Thermal resistance of air layers. 4
5.4 Thermal resistance of unheated spaces . 6
6 Total thermal resistance . 7
6.1 Total thermal resistance of a building component consisting of homogeneous layers. 7
6.2 Total thermal resistance of a building component consisting of homogeneous and
inhomogeneous layers. 7
7 Thermal transmittance . 11
Annex A (normative) Surface resistance. 12
Annex B (normative) Thermal resistance of airspaces . 15
Annex C (normative) Calculation of the thermal transmittance of components with tapered layers . 18
Annex D (normative) Corrections to thermal transmittance. 22
Bibliography . 28

ISO 6946:2007(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 6946 was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use in the
built environment, Subcommittee SC 2, Calculation methods.
This second edition cancels and replaces the first edition (ISO 6946:1996), which has been technically revised.
It also incorporates the Amendment ISO 6946:1996/Amd.1:2003.
The following changes have been made to the first edition:
⎯ information on the calculation of heat flow rates has been transferred from the Introduction to the note in
Clause 4;
⎯ 5.3.3 provides an amended basis for slightly ventilated air layers;
⎯ 5.4.2 provides clarification of the applicability of Table 3;
⎯ 5.4.3 has been completely revised;
⎯ 6.2.1 provides a new text to allow calculation of a component that is part of a complete element; it also
clarifies exceptions and the limit of applicability;
⎯ Annex B provides additional data for other temperature differences across cavities; it also provides a
correction to the formula for radiation transfer in divided airspaces;
⎯ Annex C contains an additional shape;
⎯ D.2 has been completely rewritten to clarify the intentions, the former Annex E having been deleted
(national annexes can be attached to this International Standard giving examples in accordance with local
building traditions);
⎯ D.3 provides a revised procedure for mechanical fasteners, including recessed fasteners;
⎯ D.4 does not apply in cooling situations.
iv © ISO 2007 – All rights reserved

ISO 6946:2007(E)
Introduction
This International Standard provides the means (in part) to assess the contribution that building products and
services make to energy conservation and to the overall energy performance of buildings.
INTERNATIONAL STANDARD ISO 6946:2007(E)

Building components and building elements — Thermal
resistance and thermal transmittance — Calculation method
1 Scope
This International Standard provides the method of calculation of the thermal resistance and thermal
transmittance of building components and building elements, excluding doors, windows and other glazed units,
curtain walling, components which involve heat transfer to the ground, and components through which air is
designed to permeate.
The calculation method is based on the appropriate design thermal conductivities or design thermal
resistances of the materials and products for the application concerned.
The method applies to components and elements consisting of thermally homogeneous layers (which can
include air layers).
This International Standard also provides an approximate method that can be used for elements containing
inhomogeneous layers, including the effect of metal fasteners, by means of a correction term given in
Annex D. Other cases where insulation is bridged by metal are outside the scope of this International
Standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 7345, Thermal insulation — Physical quantities and definitions
ISO 10456, Building materials and products — Hygrothermal properties — Tabulated design values and
procedures for determining declared and design thermal values
ISO 13789, Thermal performance of buildings — Transmission and ventilation heat transfer coefficients —
Calculation metho
...