SIST EN ISO 12631:2013
(Main)Thermal performance of curtain walling - Calculation of thermal transmittance (ISO 12631:2012)
Thermal performance of curtain walling - Calculation of thermal transmittance (ISO 12631:2012)
This International Standard specifies a method for calculating the thermal transmittance of curtain walls consisting of glazed and/or opaque panels fitted in, or connected to, frames. The calculation includes: - different types of glazing, e.g. glass or plastic; single or multiple glazing; with or without low emissivity coating; with cavities filled with air or other gases; - frames (of any material) with or without thermal breaks; - different types of opaque panels clad with metal, glass, ceramics or any other material. Thermal bridge effects at the rebate or connection between the glazed area, the frame area and the panel area are included in the calculation. The calculation does not include: - effects of solar radiation; - heat transfer caused by air leakage; - calculation of condensation; - effect of shutters; - additional heat transfer at the corners and edges of the curtain walling; - connections to the main building structure nor through fixing lugs; - curtain wall systems with integrated heating.
Wärmetechnisches Verhalten von Vorhangfassaden - Berechnung des Wärmedurchgangskoeffizienten (ISO 12631:2012)
Diese Norm legt ein Verfahren zur Ermittlung des Wärmedurchgangskoeffizienten von Vorhangfassaden fest, die aus verglasten und/oder opaken Paneelen, die in Rahmen eingebaut werden oder mit Rahmen verbunden sind, bestehen.
Die Berechnung umfasst
⎯ unterschiedliche Verglasungsarten, z. B. aus Glas oder Kunststoff, einfache und mehrfache
Verglasungen, Verglasungen mit oder ohne Beschichtungen mit niedrigem Emissionsgrad sowie
Verglasungen mit einem Zwischenraum, der mit Luft oder anderen Gasen gefüllt ist;
⎯ Rahmen (aus einem beliebigen Material), mit oder ohne wärmetechnische Trennung;
⎯ verschiedene Arten von opaken Paneelen, die mit Metall, Glas, Keramik oder einem anderen Material
verkleidet sind.
Die Berechnung berücksichtigt den Einfluss von Wärmebrücken am Falz oder an der Fuge zwischen der
verglasten Fläche, dem Rahmen und dem Paneel.
Folgende Faktoren werden in der Berechnung nicht berücksichtigt:
- Einflüsse aus der Sonneneinstrahlung;
- Wärmeübertragung durch Luftdurchlässigkeit;
- Tauverhalten;
- Einfluss von Abschlüssen;
- zusätzliche Wärmeübertragung an den Ecken und Kanten der Vorhangfassade;
- Verbindungen mit das Tragwerk und die dazu verwendeten Verbindungsmittel;
- Vorhangfassaden mit eingebauter Heizung.
Performance thermique des façades-rideaux - Calcul du coefficient de transmission thermique (ISO 12631:2012)
Toplotne značilnosti obešenih fasad - Izračun toplotne prehodnosti (ISO 12631:2012)
Ta mednarodni standard določa metodo za izračun toplotne prehodnosti obešenih fasad iz steklenih in/ali prosojnih plošč, nameščenih v okvirje ali povezanih z okvirji. Izračun vključuje: – različne vrste zasteklitve, npr. iz stekla ali plastike; enojna ali večkratna zasteklitev; z nanosom ali brez nanosa nizke emisivnosti; z vmesnimi prostori, napolnjenimi z zrakom ali drugimi plini; – okvirje (iz katerega koli materiala) s toplotnimi prekinitvami ali brez; – različne vrste prosojnih plošč, prevlečenih s kovino, steklom, keramiko ali drugimi materiali. Toplotni mostovi na znižanju ali stiku med zastekljenim območjem, območjem okvirja in območjem plošče so vključeni v izračun. Izračun ne vključuje: – učinkov sončnega sevanja; – prenosa toplote zaradi puščanja zraka; – izračuna kondenzacije; – učinkov polken; – dodatnega prenosa toplote v kotih in na robovih zidov za zavese; – povezav z glavno stavbno strukturo ali skozi pritrdilne spoje; – sistemov zidov za zavese z vgrajenim gretjem.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 12631:2013
01-marec-2013
1DGRPHãþD
SIST EN 13947:2007
7RSORWQH]QDþLOQRVWLREHãHQLKIDVDG,]UDþXQWRSORWQHSUHKRGQRVWL ,62
Thermal performance of curtain walling - Calculation of thermal transmittance (ISO
12631:2012)
Wärmetechnisches Verhalten von Vorhangfassaden - Berechnung des
Wärmedurchgangskoeffizienten (ISO 12631:2012)
Performance thermique des façades-rideaux - Calcul du coefficient de transmission
thermique (ISO 12631:2012)
Ta slovenski standard je istoveten z: EN ISO 12631:2012
ICS:
91.060.10 Stene. Predelne stene. Walls. Partitions. Facades
Fasade
91.120.10 Toplotna izolacija stavb Thermal insulation
SIST EN ISO 12631:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 12631:2013
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SIST EN ISO 12631:2013
EUROPEAN STANDARD
EN ISO 12631
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2012
ICS 91.120.10 Supersedes EN 13947:2006
English Version
Thermal performance of curtain walling - Calculation of thermal
transmittance (ISO 12631:2012)
Performance thermique des façades-rideaux - Calcul du Wärmetechnisches Verhalten von Vorhangfassaden -
coefficient de transmission thermique (ISO 12631:2012) Berechnung des Wärmedurchgangskoeffizienten (ISO
12631:2012)
This European Standard was approved by CEN on 30 September 2012.
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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12631:2012: E
worldwide for CEN national Members.
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SIST EN ISO 12631:2013
EN ISO 12631:2012 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 12631:2013
EN ISO 12631:2012 (E)
Foreword
This document (EN ISO 12631:2012) 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 April 2013, and conflicting national standards shall be withdrawn at the
latest by April 2013.
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 13947:2006.
According to the CEN/CENELEC Internal Regulations, the national standards organisations 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
3
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SIST EN ISO 12631:2013
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SIST EN ISO 12631:2013
INTERNATIONAL ISO
STANDARD 12631
First edition
2012-10-01
Thermal performance of curtain
walling — Calculation of thermal
transmittance
Performance thermique des façades-rideaux — Calcul du coefficient de
transmission thermique
Reference number
ISO 12631:2012(E)
©
ISO 2012
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and units . 2
3.1 Terms and definitions . 2
3.2 Symbols and units . 3
3.3 Subscripts . 3
3.4 Superscripts . 4
4 Geometrical characteristics . 4
4.1 Main principles . 4
4.2 Internal depth . 6
4.3 Boundaries of curtain wall structures . 6
5 Cut-off planes and partitioning of thermal zones . 9
5.1 Rules for thermal modelling . 9
5.2 Cut-off planes of the geometrical model . 9
6 Calculation of curtain wall transmittance . 9
6.1 Methodologies . 9
6.2 Single assessment method . 10
6.3 Component assessment method . 16
6.4 Thermal transmittance of a curtain wall built of different elements . 21
7 Input data . 21
8 Report . 22
8.1 Section drawings . 22
8.2 Overview drawing of the whole curtain wall element . 23
8.3 Values used for calculation . 23
8.4 Presentation of results . 23
Annex A (informative) Guidance for calculating the thermal transmittance U of curtain walling
cw
using the two methods . 24
Annex B (informative) Linear thermal transmittance of junctions . 25
Annex C (normative) A method for calculating the thermal effect of screws using a 2D numerical
method and the procedures specified in ISO 10077-2:2012 . 33
Annex D (normative) Ventilated and unventilated air spaces . 36
Annex E (informative) Component method: Calculation example . 39
Annex F (informative) Single assessment method: Calculation example . 45
Annex G (normative) Parallel routes in normative references . 48
Bibliography . 49
© ISO 2012 – All rights reserved iii
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SIST EN ISO 12631:2013
ISO 12631:2012(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 12631 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 89, Thermal performance of buildings and building components, the secretariat of which is held by
SIS, in collaboration with ISO Technical Committee 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).
iv © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
Introduction
The design and construction of curtain wall systems is complex. This International Standard specifies a
procedure for calculating the thermal transmittance of curtain wall structures.
Curtain walls often contain different kinds of materials, joined in different ways, and can exhibit numerous
variations of geometrical shape. With such a complex structure, the likelihood of producing thermal bridges
across the curtain wall envelope is quite high.
The results of calculations, carried out following the procedures specified in this International Standard, can be
used for comparison of the thermal transmittance of different types of curtain wall or as part of the input data
for calculating the heat used in a building. This International Standard is not suitable for determining whether
or not condensation will occur on the structure surfaces nor within the structure itself.
Two methods are given in this International Standard:
single assessment method (see 6.2);
component assessment method (see 6.3).
Guidance on the use of these two methods is given in Annex A. Calculation examples for these two methods
are given in Annex E and Annex F.
Testing according to ISO 12567-1:2010 is an alternative to this calculation method.
The thermal effects of connections to the main building structure as well as fixing lugs can be calculated
according to ISO 10211:2007.
The thermal transmittance of the frame, U , is defined according to ISO 10077-2:2012 or EN 12412-2:2003
f
together with Annex A. The thermal transmittance of glazing units, U , is defined according to the documents
g
listed in Table G.1 which does not include the edge effects. The thermal interaction of the frame and the filling
element is included in the linear thermal transmittance which is derived using the procedures specified in
ISO 10077-2:2012.
© ISO 2012 – All rights reserved v
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SIST EN ISO 12631:2013
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SIST EN ISO 12631:2013
INTERNATIONAL STANDARD ISO 12631:2012(E)
Thermal performance of curtain walling — Calculation of
thermal transmittance
1 Scope
This International Standard specifies a method for calculating the thermal transmittance of curtain walls
consisting of glazed and/or opaque panels fitted in, or connected to, frames.
The calculation includes:
different types of glazing, e.g. glass or plastic; single or multiple glazing; with or without low emissivity
coating; with cavities filled with air or other gases;
frames (of any material) with or without thermal breaks;
different types of opaque panels clad with metal, glass, ceramics or any other material.
Thermal bridge effects at the rebate or connection between the glazed area, the frame area and the panel
area are included in the calculation.
The calculation does not include:
effects of solar radiation;
heat transfer caused by air leakage;
calculation of condensation;
effect of shutters;
additional heat transfer at the corners and edges of the curtain walling;
connections to the main building structure nor through fixing lugs;
curtain wall systems with integrated heating.
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 6946:2007, Building components and building elements — Thermal resistance and thermal
transmittance — Calculation method
ISO 7345:1987, Thermal insulation — Physical quantities and definitions
© ISO 2012 – All rights reserved 1
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
ISO 10077-1:2006, Thermal performance of windows, doors and shutters — Calculation of thermal
transmittance — Part 1: General
ISO 10077-2:2012, Thermal performance of windows, doors and shutters — Calculation of thermal
transmittance — Part 2: Numerical method for frames
ISO 10211:2007, Thermal bridges in building construction — Heat flows and surface temperatures — Detailed
calculations
ISO 10291:1994, Glass in building — Determination of steady-state U values (thermal transmittance) of
multiple glazing - Guarded hot plate method
ISO 10292:1994, Glass in building — Calculation of steady-state U values (thermal transmittance) of multiple
glazing
ISO 10293:1997, Glass in building — Determination of steady-state U values (thermal transmittance) of
multiple glazing - Heat flow meter method
ISO 12567-1:2010, Thermal performance of windows and doors — Determination of thermal transmittance by
hot box method — Part 1: Complete windows and doors
EN 673:2011, Glass in building — Determination of thermal transmittance (U value) — Calculation method
EN 674:2011, Glass in building — Determination of thermal transmittance (U value) — Guarded hot plate
method
EN 675:2011, Glass in building — Determination of thermal transmittance (U value) — Heat flow meter
method
EN 12412-2:2003, Thermal performance of windows, doors and shutters — Determination of thermal
transmittance by hot-box method — Part 2: Frames
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7345:1987, ISO 6946:2007 and
Annex G apply.
NOTE Clause 4 includes descriptions of a number of geometrical characteristics of glazing units, frame sections and
panels.
2 © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
3.2 Symbols and units
Table 1 — Symbols and units
Symbol Quantity Unit
2
A area m
T thermodynamic temperature K
2
U thermal transmittance W/(m ·K)
l length m
d depth m
heat flow rate W
linear thermal transmittance W/(m·K)
∆ difference
Σ summation
emissivity
3.3 Subscripts
cw curtain walling
d developed
e external
eq equivalent
f frame
f,g frame/glazing
FE filling element
g glazing
i internal
j joint
m mullion
m,f mullion/frame
m,g mullion/glazing
n normal
p panel (opaque)
s screw
t transom
t,f transom/frame
t,g transom/glazing
tot total
TJ thermal joint at a connection between two filling elements
W window
© ISO 2012 – All rights reserved 3
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
3.4 Superscripts
* definition of areas for length-related treatment of thermal joints (see 6.2.2.3)
4 Geometrical characteristics
4.1 Main principles
The main principles of curtain walling are shown in Figures 1 and 2.
Key
1 structure fixing bracket
A-A vertical section
Figure 1 — Principle of curtain walling construction: unitised construction
4 © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
Key
1 structure fixing bracket
A-A vertical section
Figure 2 — Principle of curtain walling construction: stick construction
© ISO 2012 – All rights reserved 5
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
4.2 Internal depth
The internal depth is defined as shown in Figure 3.
Key
1 internal
2 external
d internal depth of mullion or transom
i
Figure 3 — Internal and external developed area, internal depth
4.3 Boundaries of curtain wall structures
4.3.1 General
To evaluate the thermal transmittance of façades, representative reference areas should be defined. The
following subclauses define the various areas.
6 © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
4.3.2 Boundaries of a representative reference element
The boundaries of the representative reference element shall be chosen according to the principles shown in
Figure 4.
Key
— — — — Boundaries of the representative element
Figure 4 — Boundaries of a representative reference element of a façade
© ISO 2012 – All rights reserved 7
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
4.3.3 Curtain wall areas
The representative reference element is divided into areas of different thermal properties (sash, frame,
mullion, transom, glazing units and panel sections) as shown in Figure 5.
Key
1 mullion
2 transom
3 sash and frame
4 glazing
5 panel
Figure 5 — Areas with different thermal properties
8 © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
5 Cut-off planes and partitioning of thermal zones
5.1 Rules for thermal modelling
In most cases, the façade can be partitioned into several sections by using cut-off planes so that the thermal
transmittance of the overall façade can be calculated as the area-weighted average of the thermal
transmittance of each section. The necessary input data (thermal properties of each section) can be evaluated
by measurement, two-dimensional finite element or finite difference software calculation or by tables or
diagrams. In general there are two possibilities:
the single assessment method (see 6.2);
the component assessment method (see 6.3).
The partitioning of the façade shall be performed in such a way as to avoid any significant differences in
calculation results of the façade treated as a whole and the heat flow rate through the partitioned façade.
Appropriate partitioning into several geometrical parts is achieved by choosing suitable cut-off planes.
5.2 Cut-off planes of the geometrical model
The geometrical model includes central elements (glazing units, spandrel panels etc.) and thermal joints
(mullion, transom, silicone joint etc.), which connect the different central elements. The geometrical model is
delimited by cut-off planes.
Curtain walling often contains highly conductive elements (glass and metals) which implies that significant
lateral heat flow is possible. Cut-off planes shall represent adiabatic boundaries, which can be either:
a symmetry plane, or
a plane where the heat flow through that plane is perpendicular to the plane of the curtain wall, i.e. no
edge effect is present (e.g. at least 190 mm away from the edge of a double glazing unit).
Cut-off planes may be positioned only where there is a clear adiabatic situation (i.e. the heat flow is
perpendicular to the plane). Figure 6 shows adiabatic lines (in the middle of the glass or panel far enough from
the frame) where the heat flow will be perpendicular to the glass panes.
Cut-off planes do not necessarily fall at the same place as the geometrical boundaries of a unitised element
(i.e. through the frame). The middle of a frame might not be an adiabatic boundary. This might be due to
asymmetric geometrical shape of the frame, asymmetric material properties (e.g. different conductivity of sub-
components at each side of the frame), or asymmetric connection of panels in a symmetric frame (e.g. a
frame that connects a spandrel panel and a glazing unit, or two glazing units with different thermal properties).
6 Calculation of curtain wall transmittance
6.1 Methodologies
Two methods of calculating the thermal transmittance of curtain wall systems are specified: the single
assessment method and the component assessment method.
The single assessment method (see 6.2) is based on detailed computer calculations of the heat transfer
through a complete construction including mullions, transoms, and filling elements (e.g. glazing unit, opaque
panel). The heat flow rate (between two adiabatic lines) is calculated by modelling each thermal joint between
two filling elements (opaque panel and/or glazing unit) using two-dimensional or three-dimensional finite
element analysis software. By area weighting the U-values of thermal joints and filling elements, the overall
façade U-value can be calculated. This method can be used for any curtain walling system (i.e. unitised
systems, stick systems, patent glazing, structural sealant glazing, rain screens, structural glazing).
© ISO 2012 – All rights reserved 9
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
The component assessment method (see 6.3) divides the representative element into areas of different
thermal properties, e.g. glazing units, opaque panels and frames. By area weighting the U-values of these
elements with additional correction terms describing the thermal interaction between these elements
(-values), the overall façade U-value can be calculated. This method can be used for curtain walling systems
such as unitised systems, stick systems and patent glazing. Structural silicone glazing, rain screens and
structural glazing are excluded from the component assessment method.
For the purposes of this International Standard, the term “filling element” is any façade component that has a
one-dimensional heat flow in the absence of edge effects (the flat surface being perpendicular to the heat flow
direction). Examples are glazing units and spandrel panels.
Figure 6 — Thermal section representing the full curtain wall
6.2 Single assessment method
6.2.1 Thermal transmittance of glazing units and panels (filling elements)
The thermal transmittance of opaque panels U shall be evaluated according to ISO 6946:2007. The thermal
p
transmittance of glazing units U shall be evaluated according to the documents listed in Table G.1. In some
g
cases, there is a different filling element at each side of the thermal joint (mullion, transom), so that two
thermal transmittances have to be determined.
6.2.2 Determination of the heat flow through filling element / mullion or transom / filling element
connection
6.2.2.1 General
The total heat flow rate of the complete connection shall be calculated using computer software that
tot
conforms to ISO 10211:2007 and ISO 10077-2:2012 or measured according to ISO 12567-1:2010 with the
10 © ISO 2012 – All rights reserved
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SIST EN ISO 12631:2013
ISO 12631:2012(E)
filling elements positioned between the adiabatic lines. The modelling of screws (if present) in the two
dimensional calculation shall be performed according to Annex C.
Since the heat flow rate is determined between the two adiabatic boundaries, it represents the heat flow
through the filling elements, the thermal joint (e.g. mullion/transom) and also the lateral heat flow (edge
effects) of the interaction between the two filling elements.
Therefore, represents the total heat flow rate that results from making a thermal joint between two filling
tot
elements and includes:
heat flow rate straight through filling element 1 and filling element 2 (one dimensional heat flow
perpendicular to the surface of the filling element);
heat flow rate through the thermal joint that is used to connect the two filling elements together (e.g. a
frame in a framed curtain wall, a silicone joint in case of structural glazing);
lateral and edge heat-flows due to the thermal interaction between the filling elements and the thermal
joint and due to the edge constructions of the two individual filling elements (e.g. glass spacer).
As in most cases these different heat flows are difficult to separate, and to assign to a specific sub-component
of the thermal joint, it is appropriate to split the overall heat flow through a thermal joint into only three parts
(see Figure 7a):
the heat flow rate through filling element 1 without the presence of the thermal joint (i.e. the heat
FE1
flow derived from the centre U-value of filling element 1);
the heat flow rate through filling element 2 without the presence of the thermal joint (i.e. the heat
FE2
flow derived from the centre U-value of filling element 2);
the heat flow rate which is the additional heat flow rate due to making a thermal joint (which includes
TJ
direct and lateral heat flows of all joint edges and the thermal joint itself excluding the one dimensional
heat flow through the filling elements).
There are two ways of allowing for the additional heat flow rate , which are equivalent and either approach
TJ
will yield the same result for the thermal transmittance of the curtain wall. The possibilities are:
consider the heat flow rate in terms of an area-related joint thermal transmittance U ;
TJ TJ
consider the heat flow
...
SLOVENSKI STANDARD
oSIST prEN ISO 12631:2011
01-februar-2011
7RSORWQH]QDþLOQRVWLREHãHQLKIDVDG,]UDþXQWRSORWQHSUHKRGQRVWL ,62',6
Thermal performance of curtain walling - Calculation of thermal transmittance (ISO/DIS
12631:2010)
Wärmetechnisches Verhalten von Vorhangfassaden - Berechnung des
Wärmedurchgangskoeffizienten (ISO/DIS 12631:2010)
Performance thermique des façades-rideaux - Calcul du coefficient de transmission
thermique (ISO/DIS 12631:2010)
Ta slovenski standard je istoveten z: prEN ISO 12631
ICS:
91.060.10 Stene. Predelne stene. Walls. Partitions. Facades
Fasade
91.120.10 Toplotna izolacija stavb Thermal insulation
oSIST prEN ISO 12631:2011 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 12631:2011
---------------------- Page: 2 ----------------------
oSIST prEN ISO 12631:2011
EUROPEAN STANDARD
DRAFT
prEN ISO 12631
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2010
ICS 91.120.10 Will supersede EN 13947:2006
English Version
Thermal performance of curtain walling - Calculation of thermal
transmittance (ISO/DIS 12631:2010)
Performance thermique des façades-rideaux - Calcul du Wärmetechnisches Verhalten von Vorhangfassaden -
coefficient de transmission thermique (ISO/DIS Berechnung des Wärmedurchgangskoeffizienten (ISO/DIS
12631:2010) 12631:2010)
This draft European Standard is submitted to CEN members for parallel enquiry. It has been drawn up by the Technical Committee
CEN/TC 89.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 12631:2010: E
worldwide for CEN national Members.
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oSIST prEN ISO 12631:2011
prEN ISO 12631:2010 (E)
Contents Page
Foreword .3
2
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oSIST prEN ISO 12631:2011
prEN ISO 12631:2010 (E)
Foreword
This document (prEN ISO 12631:2010) 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 document is currently submitted to the parallel Enquiry.
This document will supersede EN 13947:2006.
3
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oSIST prEN ISO 12631:2011
DRAFT INTERNATIONAL STANDARD ISO/DIS 12631
ISO/TC 163/SC 2 Secretariat: SN
Voting begins on: Voting terminates on:
2010-11-04 2011-04-04
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Thermal performance of curtain walling — Calculation of
thermal transmittance
Performance thermique des façades-rideaux — Calcul du coefficient de transmission thermique
ICS 91.120.10
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the European Committee for Standardization (CEN), and processed
under the CEN-lead mode of collaboration as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel
five-month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments received, will be
submitted to a parallel two-month approval vote in ISO and formal vote in CEN.
In accordance with the provisions of Council Resolution 15/1993 this document is circulated in
the English language only.
Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est distribué
en version anglaise seulement.
To expedite distribution, this document is circulated as received from the committee secretariat.
ISO Central Secretariat work of editing and text composition will be undertaken at publication
stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
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RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
©
International Organization for Standardization, 2010
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Contents Page
Foreword .v
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions, symbols and units .2
3.1 Terms and definitions .2
3.2 Symbols and units.2
3.3 Subscripts .2
3.4 Superscripts.3
4 Geometrical characteristics .3
4.1 Main principles .3
4.2 Developed areas and internal depth.6
4.3 Boundaries of curtain wall structures.6
4.3.1 6
4.3.2 Boundaries of a representative reference element.7
4.3.3 Curtain wall areas.8
5 Cut-off planes and partitioning of thermal zones .9
5.1 Rules for thermal modelling.9
5.2 Cut-off planes of the geometrical model.9
6 Calculation of curtain wall transmittance .9
6.1 Methodologies .9
6.2 Single assessment method .10
6.2.1 Thermal transmittance of glazing units and panels (filling elements).10
6.2.2 Determination of the heat flow through filling element / mullion or transom / filling
element connection.10
6.2.3 Determination of the overall thermal transmittance of a curtain wall (U ).15
cw
6.3 Component assessment method.16
6.3.1 General .16
6.3.2 Definition of areas .16
6.3.3 Thermal transmittance of glazing units and panels (filling elements).19
6.3.4 Thermal transmittance of frames, mullions and transoms.19
6.3.5 Linear thermal transmittance .20
6.4 Thermal transmittance of a curtain wall built of different elements .22
7 Input data .22
8 Report.23
8.1 Section drawings.23
8.2 Overview drawing of the whole curtain wall element.23
8.3 Values used for calculation.23
8.4 Presentation of results.23
Annex A (informative) Guidance for calculating the thermal transmittance U of curtain walling
cw
using the two methods .24
Annex B (informative) Linear thermal transmittance of junctions.25
Annex C (normative) A method for calculating the thermal effect of screws using a 2D numerical
method and the procedures specified in ISO 10077-2.33
C.1 General.33
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C.2 Calculation of the equivalent thermal conductivity of the screw λ . 34
s,eq
C.3 Consideration of screw heads and washers.36
Annex D (normative) Ventilated and unventilated air spaces . 37
Annex E (informative) Component method: Calculation example . 40
E.1 Data for examples. 40
E.2 Frames . 42
E.2.1 Definition and evaluation of areas . 42
E.2.2 Evaluation of U values . 43
f
E.3 Glazing units . 43
E.3.1 Definition and evaluation of areas . 43
E.3.2 Evaluation of U values . 43
g
E.3.3 Definition of l and evaluation of Ψ , Ψ and Ψ . 43
g g m,f t,f
E.4 Panels. 44
E.4.1 Definition and evaluation of areas . 44
E.4.2 Evaluation of U values . 44
p
E.4.3 Definition of l and evaluation of the Ψ values . 44
p p
E.4.4 Calculation of a complete element. 45
Annex F (informative) Single assessment method: Calculation example. 46
F.1 General description of examples . 46
F.2 Centre U-value of the glazing unit. 47
F.3 Centre U-value of the spandrel panel . 47
F.4 U-values of thermal joints. 47
F.5 Overall U-value of the curtain wall. 48
Bibliography. 49
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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 12631 was 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, Subcommittee SC 2, Calculation methods, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This document is currently submitted to the parallel Enquiry.
Introduction
The design and construction of curtain wall systems is complex. This standard specifies a procedure for
calculating the thermal transmittance of curtain wall structures.
Curtain walls often contain different kinds of materials, joined in different ways, and can exhibit numerous
variations of geometrical shape. With such a complex structure, the likelihood of producing thermal bridges
across the curtain wall envelope is quite high.
The results of calculations, carried out following the procedures specified in this standard, can be used for
comparison of the thermal transmittance of different types of curtain wall or as part of the input data for
calculating the heat used in a building. This standard is not suitable for determining whether or not
condensation will occur on the structure surfaces nor within the structure itself.
Two methods are given in this standard:
⎯ single assessment method (see 6.2);
⎯ component assessment method (see 6.3).
Guidance on the use of these two methods is given in Annex A. Calculation examples for these two methods
are given in Annex E and Annex F.
Testing according to ISO 12567-1 is an alternative to this calculation method.
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oSIST prEN ISO 12631:2011
ISO/DIS 12631
The thermal effects of connections to the main building structure as well as fixing lugs can be calculated
according to ISO 10211.
The thermal transmittance of the frame, U , is defined according to ISO 10077-2 or EN 12412-2 together with
f
Annex A. The thermal transmittance of glazing units, U , is defined according to EN 673, EN 674 or EN 675
g
which do not include the edge effects. The thermal interaction of the frame and the filling element is included
in the linear thermal transmittance Ψ which is derived using the procedures specified in ISO 10077-2.
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oSIST prEN ISO 12631:2011
DRAFT INTERNATIONAL STANDARD ISO/DIS 12631
Thermal performance of curtain walling — Calculation of
thermal transmittance
1 Scope
This standard specifies a method for calculating the thermal transmittance of curtain walls consisting of glazed
and/or opaque panels fitted in, or connected to, frames.
The calculation includes:
⎯ different types of glazing, e.g. glass or plastic; single or multiple glazing; with or without low emissivity
coating; with cavities filled with air or other gases;
⎯ frames (of any material) with or without thermal breaks;
⎯ different types of opaque panels clad with metal, glass, ceramics or any other material.
Thermal bridge effects at the rebate or connection between the glazed area, the frame area and the panel
area are included in the calculation.
The calculation does not include:
⎯ effects of solar radiation;
⎯ heat transfer caused by air leakage;
⎯ calculation of condensation;
⎯ effect of shutters;
⎯ additional heat transfer at the corners and edges of the curtain walling;
⎯ connections to the main building structure nor through fixing lugs;
⎯ curtain wall systems with integrated heating.
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.
EN 673:1997, Glass in building — Determination of thermal transmittance (U value) — Calculation method
EN 674, Glass in building — Determination of thermal transmittance (U value) — Guarded hot plate method
EN 675, Glass in building — Determination of thermal transmittance (U value) — Heat flow meter method
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EN 12412-2, Thermal performance of windows, doors and shutters — Determination of thermal transmittance
by hot box method — Part 2: Frames
ISO 6946:2007, Building components and building elements — Thermal resistance and thermal transmittance
— Calculation method
ISO 7345:1995, Thermal insulation — Physical quantities and definitions
ISO 10077-1:2006, Thermal performance of windows, doors and shutters — Calculation of thermal
transmittance — Part 1: General
DIS 10077-2:2009, Thermal performance of windows, doors and shutters — Calculation of thermal
transmittance — Part 2: Numerical method for frames
ISO 10211:2007, Thermal bridges in building construction — Heat flows and surface temperatures — Detailed
calculations
ISO 12567-1:2000, Thermal performance of windows and doors — Determination of thermal transmittance by
hot box method — Part 1: Complete windows and doors
3 Terms and definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 673:1997, ISO 7345:1995,
ISO 6946:2007 and the following apply.
NOTE Clause 4 includes descriptions of a number of geometrical characteristics of glazing units, frame sections and
panels.
3.2 Symbols and units
Table 1 — Symbols and units
Symbol Quantity Unit
2
A area m
T thermodynamic temperature K
2
U thermal transmittance W/(m ·K)
l length m
d depth m
Φ heat flow rate W
Ψ linear thermal transmittance W/(m·K)
Δ difference
Σ summation
ε emissivity
3.3 Subscripts
cw curtain walling
d developed
e external
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eq equivalent
f frame
f,g frame/glazing
FE filling element
g glazing
i internal
j joint
m mullion
m,f mullion/frame
m,g mullion/glazing
n normal
p panel (opaque)
s screw
t transom
t,f transom/frame
t,g transom/glazing
tot total
TJ thermal joint at a connection between two filling elements
W window
3.4 Superscripts
* definition of areas for length-related treatment of thermal joints (see 6.2.2.3)
4 Geometrical characteristics
4.1 Main principles
The main principles of curtain walling are shown in Figures 1 and 2.
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Key
1 structure fixing bracket
A-A vertical section
Figure 1 — Principle of curtain walling construction: unitised construction
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Key
1 structure fixing bracket
A-A vertical section
Figure 2 — Principle of curtain walling construction: stick construction
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4.2 Developed areas and internal depth
Internal and external developed areas and internal depth are defined as shown in Figure 3.
Key
1 internal
2 external
d internal depth of mullion or transom
i
A internal developed area
d,i
A external developed area
d,e
Figure 3 — Internal and external developed area, internal depth
4.3 Boundaries of curtain wall structures
4.3.1
To evaluate the thermal transmittance of façades representative reference areas should be defined. The
following subclauses define the various areas.
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4.3.2 Boundaries of a representative reference element
The boundaries of the representative reference element shall be chosen according to the principles shown in
Figure 4.
Figure 4 — Boundaries of a representative reference element of a façade
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4.3.3 Curtain wall areas
The representative reference element is divided into areas of different thermal properties (sash, frame,
mullion, transom, glazing units and panel sections) (see Figure 5).
Key
1 mullion
2 transom
3 sash and frame
4 glazing
5 panel
Figure 5 — Areas with different thermal properties
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5 Cut-off planes and partitioning of thermal zones
5.1 Rules for thermal modelling
In most cases the façade can be partitioned into several sections by using cut-off planes so that the thermal
transmittance of the overall façade can be calculated as the area-weighted average of the thermal
transmittance of each section. The necessary input data (thermal properties of each section) can be evaluated
by measurement, two-dimensional finite element or finite difference software calculation or by tables or
diagrams. In general there are two possibilities:
⎯ the single assessment method (see 6.2);
⎯ the component assessment method (see 6.3).
The partitioning of the façade shall be performed in such a way as to avoid any significant differences in
calculation results of the façade treated as a whole and the heat flow rate through the partitioned façade.
Appropriate partitioning into several geometrical parts is achieved by choosing suitable cut-off planes.
5.2 Cut-off planes of the geometrical model
The geometrical model includes central elements (glazing units, spandrel panels etc.) and thermal joints
(mullion, transom, silicone joint etc.), which connect the different central elements. The geometrical model is
delimited by cut-off planes.
Curtain walling often contains highly conductive elements (glass and
...
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