EN ISO 12241:2022

SLOVENSKI STANDARD
01-september-2022
Nadomešča:
SIST EN ISO 12241:2008
Toplotna izolacija za opremo stavb in industrijske inštalacije - Pravila za računanje
(ISO 12241:2022)
Thermal insulation for building equipment and industrial installations - Calculation rules
(ISO 12241:2022)
Wärmedämmung an haus- und betriebstechnischen Anlagen - Berechnungsregeln (ISO
12241:2022)
Isolation thermique des équipements de bâtiments et des installations industrielles -
Méthodes de calcul (ISO 12241:2022)
Ta slovenski standard je istoveten z: EN ISO 12241:2022
ICS:
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
91.140.01 Napeljave v stavbah na Installations in buildings in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 12241
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2022
EUROPÄISCHE NORM
ICS 91.120.10; 91.140.01 Supersedes EN ISO 12241:2008
English Version
Thermal insulation for building equipment and industrial
installations - Calculation rules (ISO 12241:2022)
Isolation thermique des équipements de bâtiments et Wärmedämmung an haus- und betriebstechnischen
des installations industrielles - Méthodes de calcul (ISO Anlagen - Berechnungsregeln (ISO 12241:2022)
12241:2022)
This European Standard was approved by CEN on 29 May 2022.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, 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: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12241:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 12241:2022) 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 December 2022, and conflicting national standards
shall be withdrawn at the latest by December 2022.
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 supersedes EN ISO 12241:2008.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 12241:2022 has been approved by CEN as EN ISO 12241:2022 without any modification.

INTERNATIONAL ISO
STANDARD 12241
Third edition
2022-06
Thermal insulation for building
equipment and industrial
installations — Calculation rules
Isolation thermique des équipements de bâtiments et des installations
industrielles — Méthodes de calcul
Reference number
ISO 12241:2022(E)
ISO 12241:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 12241:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 1
3.3 Subscripts . 3
4 Calculation rules and formulae of heat transfer . 4
4.1 Fundamental formulae for heat transfer . 4
4.1.1 General . 4
4.1.2 Thermal conduction . 4
4.1.3 Surface coefficient of heat transfer . 9
4.1.4 External surface resistance . 16
4.1.5 Thermal transmittance . 16
4.1.6 Heat flow rate . 18
4.1.7 Temperatures of the layer boundaries. 18
4.2 Determination of the influence of thermal bridges . 19
4.2.1 General . 19
4.2.2 Insulation system related thermal bridges . 19
4.2.3 Installation related thermal bridges . 19
4.3 Determination of total heat flow rate for plane walls, pipes and spheres .20
4.4 Surface temperature .20
4.5 Prevention of surface condensation . 21
5 Calculation of the temperature change in pipes, vessels, and containers .22
5.1 General .22
5.2 Longitudinal temperature change in a pipe . 23
5.3 Temperature change and cooling times in pipes, vessels, and containers .23
6 Calculation of cooling and freezing times of stationary liquids.24
6.1 Calculation of the cooling time to prevent the freezing of water in a pipe . 24
6.2 Calculation of the freezing time of water in a pipe . 25
7 Calculation of heat loss for underground pipelines .26
7.1 General . 26
7.2 Single line without channels . 26
7.2.1 Uninsulated pipe .26
7.2.2 Insulated pipe . 27
7.3 Other cases .28
Annex A (informative) Thermal bridges .29
Annex B (informative) Examples .43
Bibliography .52
iii
ISO 12241:2022(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 possib
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