SIST EN ISO 14683:2008
(Main)Thermal bridges in building construction - Linear thermal transmittance - Simplified methods and default values (ISO 14683:2007)
Thermal bridges in building construction - Linear thermal transmittance - Simplified methods and default values (ISO 14683:2007)
This International Standard deals with simplified methods for determining heat flows through linear thermal bridges which occur at junctions of building elements. This International Standard specifies requirements relating to thermal bridge catalogues and manual calculation methods. Default values of linear thermal transmittance are given in Annex A for information.
Wärmebrücken im Hochbau - Längenbezogener Wärmedurchgangskoeffizient - Vereinfachte Verfahren und Anhaltswerte (ISO 14683:2007)
Diese Norm behandelt vereinfachte Verfahren zur Bestimmung der Wärmeströme durch linienförmige Wärme-
brücken, die an Bauteilverbindungen auftreten.
Sie legt Anforderungen an Wärmebrückenkataloge und Handrechenverfahren fest.
In einem informativen Anhang sind Anhaltswerte des längenbezogenen Wärmedurchgangskoeffizienten ange-
geben.
Ponts thermiques dans les bâtiments - Coefficient de transmission thermique linéique - Méthodes simplifiées et valeurs par défaut (ISO 14683:2007)
L'ISO 14683:2007 traite des méthodes simplifiées pour la détermination des flux de chaleur à travers les ponts thermiques linéaires qui se produisent aux jonctions de parois de bâtiments.
L'ISO 14683:2007 établit des exigences concernant les catalogues de ponts thermiques et les méthodes manuelles de calcul.
Des valeurs par défaut des coefficients de transmission thermique linéique sont indiquées dans l'Annexe A pour information.
Toplotni mostovi v stavbah - Linearna toplotna prehodnost - Poenostavljena metoda in privzete vrednosti (ISO 14683:2007)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 14683:2008
01-junij-2008
1DGRPHãþD
SIST EN ISO 14683:2000
Toplotni mostovi v stavbah - Linearna toplotna prehodnost - Poenostavljena
metoda in privzete vrednosti (ISO 14683:2007)
Thermal bridges in building construction - Linear thermal transmittance - Simplified
methods and default values (ISO 14683:2007)
Wärmebrücken im Hochbau - Längenbezogener Wärmedurchgangskoeffizient -
Vereinfachte Verfahren und Anhaltswerte (ISO 14683:2007)
Ponts thermiques dans les bâtiments - Coefficient de transmission thermique linéique -
Méthodes simplifiées et valeurs par défaut (ISO 14683:2007)
Ta slovenski standard je istoveten z: EN ISO 14683:2007
ICS:
91.120.10 Toplotna izolacija stavb Thermal insulation
SIST EN ISO 14683:2008 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN ISO 14683
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2007
ICS 91.120.10 Supersedes EN ISO 14683:1999
English Version
Thermal bridges in building construction - Linear thermal
transmittance - Simplified methods and default values (ISO
14683:2007)
Ponts thermiques dans les bâtiments - Coefficient linéique Wärmebrücken im Hochbau - Längenbezogener
de transmission thermique - Méthodes simplifiées et Wärmedurchgangskoeffizient - Vereinfachte Verfahren und
valeurs par défaut (ISO 14683:2007) Anhaltswerte (ISO 14683:2007)
This European Standard was approved by CEN on 7 November 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 14683:2007: E
worldwide for CEN national Members.
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EN ISO 14683:2007 (E)
Contents Page
Foreword.3
2
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EN ISO 14683:2007 (E)
Foreword
This document (EN ISO 14683:2007) 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 14683:1999.
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 14683:2007 has been approved by CEN as a EN ISO 14683:2007 without any modification.
3
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INTERNATIONAL ISO
STANDARD 14683
Second edition
2007-12-01
Thermal bridges in building
construction — Linear thermal
transmittance — Simplified methods and
default values
Ponts thermiques dans les bâtiments — Coefficient linéique de
transmission thermique — Méthodes simplifiées et valeurs par défaut
Reference number
ISO 14683:2007(E)
©
ISO 2007
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ISO 14683:2007(E)
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ii © ISO 2007 – All rights reserved
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ISO 14683:2007(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
3.3 Subscripts .2
4 Influence of thermal bridges on overall heat transfer.3
4.1 Transmission heat transfer coefficient .3
4.2 Linear thermal transmittance .3
4.3 Internal and external dimensions.4
5 Determination of linear thermal transmittance.4
5.1 Available methods and expected accuracy .4
5.2 Numerical calculations.4
5.3 Thermal bridge catalogues .4
5.4 Manual calculation methods.5
5.5 Default values of linear thermal transmittance.5
Annex A (informative) Default values of linear thermal transmittance.6
Annex B (informative) Example of the use of default values of linear thermal transmittance in
calculating the heat transfer coefficient.19
Bibliography .23
© ISO 2007 – All rights reserved iii
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ISO 14683:2007(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 14683 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 14683:1999), which has been technically
revised.
The following principal changes have been made to the first edition:
⎯ the Scope has been amended to remove the restriction on window and door frames and curtain walling,
and specifies that the default values of linear thermal transmittance are provided for information;
⎯ 5.2 is a new subclause replacing some elements previously contained in 4.2;
⎯ 5.5 is a summary into a short text of the former 5.4, the remainder of which has been transferred into
informative Annex A;
⎯ Annex A contains values of linear thermal transmittance which have all been reviewed, many of them
amended upwards as a result of changing the basis in Table A.1 (intermediate floor slabs thickness of
200 mm instead of 150 mm; frames in openings of thickness 60 mm instead of 100 mm).
iv © ISO 2007 – All rights reserved
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ISO 14683:2007(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.
Thermal bridges in building constructions give rise to changes in heat flow rates and surface temperatures
compared with those of the unbridged structure. These heat flow rates and temperatures can be precisely
determined by numerical calculation in accordance with ISO 10211. However, for linear thermal bridges, it is
often convenient to use simplified methods or tabulated values to obtain an estimate of their linear thermal
transmittance.
The effect of repeating thermal bridges which are part of an otherwise uniform building element, such as wall
ties penetrating a thermal insulation layer or mortar joints in lightweight blockwork, needs to be included in the
calculation of the thermal transmittance of the building element concerned, in accordance with ISO 6946.
Although not covered by this International Standard, it is worth noting that thermal bridges can also give rise to
low internal surface temperatures, with an associated risk of surface condensation or mould growth.
© ISO 2007 – All rights reserved v
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INTERNATIONAL STANDARD ISO 14683:2007(E)
Thermal bridges in building construction — Linear thermal
transmittance — Simplified methods and default values
1 Scope
This International Standard deals with simplified methods for determining heat flows through linear thermal
bridges which occur at junctions of building elements.
This International Standard specifies requirements relating to thermal bridge catalogues and manual
calculation methods.
Default values of linear thermal transmittance are given in Annex A for information.
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 10211, Thermal bridges in building construction — Heat flows and surface temperatures — Detailed
calculations
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 and the following apply.
3.1.1
linear thermal bridge
thermal bridge with a uniform cross section along one of the three orthogonal axes
3.1.2
point thermal bridge
localized thermal bridge whose influence can be represented by a point thermal transmittance
3.1.3
linear thermal transmittance
heat flow rate in the steady state divided by length and by the temperature difference between the
environments on either side of a thermal bridge
NOTE The linear thermal transmittance is a quantity describing the influence of a linear thermal bridge on the total
heat flow.
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ISO 14683:2007(E)
3.1.4
point thermal transmittance
heat flow rate in the steady state divided by the temperature difference between the environments on either
side of a thermal bridge
NOTE The point thermal transmittance is a quantity describing the influence of a point thermal bridge on the total
heat flow.
3.1.5
transmission heat transfer coefficient
heat flow rate due to thermal transmission through the fabric of a building, divided by the difference between
the environment temperatures on either side of the construction
3.2 Symbols and units
Symbol Quantity Unit
2
A area
m
b width m
d thickness m
H transmission heat transfer coefficient W/K
T
H direct transmission heat transfer coefficient W/K
D
H transmission heat transfer coefficient through unconditioned spaces W/K
U
l length m
2
R thermal resistance
m ⋅K/W
2
R external surface resistance
m ⋅K/W
se
2
R internal surface resistance
m ⋅K/W
si
2
U thermal transmittance
W/(m ⋅K)
Celsius temperature °C
θ
design thermal conductivity W/(m·K)
λ
heat flow rate W
Φ
Ψ linear thermal transmittance W/(m⋅K)
point thermal transmittance W/K
χ
3.3 Subscripts
Subscript Definition
e external
i internal
oi overall internal
2 © ISO 2007 – All rights reserved
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ISO 14683:2007(E)
4 Influence of thermal bridges on overall heat transfer
4.1 Transmission heat transfer coefficient
Between internal and external environments with temperatures θ and θ respectively, the transmission heat
i e
flow rate through the building envelope, Φ, is calculated using Equation (1):
Φθ=−H θ (1)
()
Ti e
The transmission heat transfer coefficient, H , is calculated using Equation (2):
T
H=+HH+H (2)
TD g U
where
H is the direct heat transfer coefficient through the building envelope defined by Equation (3);
D
H is the ground heat transfer coefficient calculated in accordance with ISO 13370;
g
H is the heat transfer coefficient through unconditioned spaces calculated in accordance with
U
ISO 13789.
4.2 Linear thermal transmittance
The calculation of the transmission heat transfer coefficient includes the contribution due to thermal bridges,
according to Equation (3):
HA=+U l Ψ+ χ (3)
D∑∑ii k k∑ j
ik j
where
2
A is the area of element i of the building envelope, in m ;
i
2
U is the thermal transmittance of element i of the building envelope, in W/(m ⋅K);
i
l is the length of linear thermal bridge k, in m;
k
Ψ is the linear thermal transmittance of linear thermal bridge k, in W/(m⋅K);
k
χ
is the point thermal transmittance of the point thermal bridge j, in W/K.
j
In general, the influence of point thermal bridges (insofar as they result from the intersection of linear thermal
bridges) can be neglected and so the correction term involving point thermal bridges can be omitted from
Equation (3). If, however, there are significant point thermal bridges, then the point thermal transmittances
should be calculated in accordance with ISO 10211.
Linear thermal bridges are generally liable to occur at the following locations in a building envelope:
⎯ at junctions between external elements (corners of walls, wall to roof, wall to floor);
⎯ at junctions of internal walls with external walls and roofs;
⎯ at junctions of intermediate floors with external walls;
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ISO 14683:2007(E)
⎯ at columns in external walls;
⎯ around windows and doors.
4.3 Internal and external dimensions
There are three dimension systems commonly in use:
⎯ internal dimensions, measured between the finished internal faces of each room in a building (thus
excluding the thickness of internal partitions);
⎯ overall internal dimensions, measured between the finished internal faces of the external elements of the
building (thus including the thickness of internal partitions);
⎯ external dimensions, measured between the finished external faces of the external elements of the
building.
These are described further in ISO 13789.
Any of these dimension systems may be used, provided that the system chosen is used consistently for all
parts of the building construction. Linear thermal transmittance values depend on the system used, i.e. on the
areas used for one-dimensional heat flow in AU in Equation (3), but the total transmission coefficient H
T
∑ ii
i
is the same provided that all thermal bridges are taken into account.
5 Determination of linear thermal transmittance
5.1 Available methods and expected accuracy
When selecting a particular method, its accuracy should reflect the accuracy required in calculating the overall
heat transfer, taking into account the lengths of the linear thermal bridges. Possible methods for determining
Ψ include numerical calculations (typical accuracy ± 5 %), thermal bridge catalogues (typical accuracy
± 20 %), manual calculations (typical accuracy ± 20 %), and default values (typical accuracy 0 % to 50 %).
The methods are discussed further in 5.2 to 5.5.
Where the details are not yet designed, but the size and main form of the building is defined, such that the
areas of the different elements of the building envelope such as roofs, walls and floors are known, only a
rough estimate of the contributions of thermal bridges to the overall heat loss can be made.
When sufficient information is available, more accurate values of Ψ for each of the linear thermal bridges can
be obtained by comparing the particular detail with the best fitting example from a thermal bridge catalogue
and using that value of Ψ. Manual calculation methods can also be used at this stage.
When full details are known, all the methods to determine Ψ may be used, including numerical calculations
which give the most precise value forΨ.
5.2 Numerical calculations
The linear thermal transmittance, Ψ, shall be calculated in accordance with ISO 10211.
Any calculation of linear thermal transmittance, Ψ, shall state the system of dimensions on which it is based.
5.3 Thermal bridge catalogues
Examples of building details in thermal bridge catalogues have essentially fixed parameters (e.g. fixed
dimensions and materials) and so are less flexible than calculations
...
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