EN ISO 13788:2001
(Main)Hygrothermal performance of building components and building elements - Internal surface temperature to avoid critical surface humidity and interstitial condensation - Calculation methods (ISO 13788:2001)
Hygrothermal performance of building components and building elements - Internal surface temperature to avoid critical surface humidity and interstitial condensation - Calculation methods (ISO 13788:2001)
This standard gives calculation methods for:
a) The internal surface temperature of a building component or building element below which mould growth is likely, given the internal temperature and relative humidity - the method can also be used to assess the risk of other surface condensation problems.
b) The assessment of the risk of interstitial condensation due to water vapour diffusion. The method used assumes built-in water has dried out and does not take account of a number of important physical phenomena including:
- the dependence of thermal conductivity on moisture content;
- the release and absorption of latent heat;
- the variation of material properties with moisture content;
- capillary suction and liquid moisture transfer within materials;
- air movement through cracks or within air spaces;
- the hygroscopic moisture capacity of materials.
Consequently the method is applicable only to structures where these effects are negligible.
Wärme- und feuchtetechnisches Verhalten von Bauteilen und Bauelementen - Raumseitige Oberflächentemperatur zur Vermeidung kritischer Oberflächenfeuchte und Tauwasserbildung im Bauteilinneren - Berechnungsverfahren (ISO 13788:2001)
Diese Norm beschreibt Verfahren
a) zur Berechnung der raumseitigen Oberflächentemperatur von Bauteilen oder Bauelementen, unterhalb welcher bei der gegebenen Innentemperatur und relativen Luftfeuchte ein Befall durch Schimmel wahrscheinlich ist; ob ein Risiko besteht, dass im Zusammenhang mit der Tauwasserbildung auf der Oberfläche andere Probleme auftreten könnten, lässt sich ebenfalls mit dem Verfahren beurteilen; sowie
b) zur Berechnung der Gefahr der Tauwasserbildung im Bauteilinneren infolge von Wasserdampfdiffusion. Beim angewendeten Verfahren wird vorausgesetzt, dass die Rohbaufeuchte ausgetrocknet ist. Nicht berücksichtigt wurde eine Reihe von wichtigen physikalischen Eigenschaften, einschließlich:
- Abhängigkeit der Wärmeleitfähigkeit vom Feuchtegehalt;
- Freisetzung und Verbrauch latenter Wärme;
- Veränderungen der Stoffeigenschaften in Abhängigkeit vom Feuchtegehalt;
- Saugwirkung von Kapillaren und Transport von Feuchte in der flüssigen Phase in Baustoffen;
- Luftbewegung durch Spalten oder in Luftschichten;
- Hygroskopisches Verhalten von Baustoffen.
Folglich gilt das Verfahren nur für Bauwerke, bei denen diese Wirkungen vernachlässigbar sind.
Performance hygrothermique des composants et parois de bâtiments - Température superficielle intérieure permettant d'éviter l'humidité superficielle critique et la condensation dans la masse - Méthodes de calcul (ISO 13788:2001)
La présente norme donne des méthodes de calcul permettant de déterminer : a) la température superficielle intérieure minimale d'un composant ou d'une paroi de bâtiment nécessaire pour rendre improbable le développement de moisissures, compte tenu de la température et de l'humidité relative intérieures. Cette méthode peut également être utilisée pour évaluer le risque d'autres problèmes de condensation superficielle ; b) le risque de condensation dans la masse due à la diffusion de vapeur d'eau. La méthode utilisée repose sur l'hypothèse que toute humidité incorporée a disparu et ne tient pas compte d'un certain nombre de phénomènes physiques importants, tels que : - l'influence de la teneur en humidité sur la conductivité thermique de la teneur en humidité - le dégagement et l'absorption de chaleur latente ; - la variation des propriétés de matériaux avec la teneur en humidité - la succion capillaire et le transfert d'humidité à l'état liquide dans les matériaux - les déplacements d'air par les fissures ou dans les espaces d'air - la capacité hygroscopique des matériaux. Par conséquent, cette méthode ne s'applique qu'aux structures dans lesquelles ces effets sont négligeables.
Higrotermalne obnašanje sestavnih delov stavb in elementov stavb – Notranja površinska temperatura za preprečevanje kritične vlage ob površini in kondenzacije v konstrukciji – Računska metoda (ISO 13788:2001)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2002
+LJURWHUPDOQRREQDãDQMHVHVWDYQLKGHORYVWDYELQHOHPHQWRYVWDYE±1RWUDQMD
SRYUãLQVNDWHPSHUDWXUD]DSUHSUHþHYDQMHNULWLþQHYODJHRESRYUãLQLLQ
NRQGHQ]DFLMHYNRQVWUXNFLML±5DþXQVNDPHWRGD ,62
Hygrothermal performance of building components and building elements - Internal
surface temperature to avoid critical surface humidity and interstitial condensation -
Calculation methods (ISO 13788:2001)
Wärme- und feuchtetechnisches Verhalten von Bauteilen und Bauelementen -
Raumseitige Oberflächentemperatur zur Vermeidung kritischer Oberflächenfeuchte und
Tauwasserbildung im Bauteilinneren - Berechnungsverfahren (ISO 13788:2001)
Performance hygrothermique des composants et parois de bâtiments - Température
superficielle intérieure permettant d'éviter l'humidité superficielle critique et la
condensation dans la masse - Méthodes de calcul (ISO 13788:2001)
Ta slovenski standard je istoveten z: EN ISO 13788:2001
ICS:
91.120.10 Toplotna izolacija stavb Thermal insulation
91.120.30 =DãþLWDSUHGYODJR Waterproofing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN ISO 13788
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2001
ICS
English version
Hygrothermal performance of building components and building
elements - Internal surface temperature to avoid critical surface
humidity and interstitial condensation - Calculation methods
(ISO 13788:2001)
Performance hygrothermique des composants et parois de Wärme- und feuchtetechnisches Verhalten von Bauteilen
bâtiments - Température superficielle intérieure permettant und Bauelementen - Raumseitige Oberflächentemperatur
d'éviter l'humidité superficielle critique et la condensation zur Vermeidung kritischer Oberflächenfeuchte und
dans la masse - Méthodes de calcul (ISO 13788:2001) Tauwasserbildung im Bauteilinneren -
Berechnungsverfahren (ISO 13788:2001)
This European Standard was approved by CEN on 18 October 2000.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, 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
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13788:2001 E
worldwide for CEN national Members.
Page 2
Contents
Page
Foreword 3
Introduction 3
1Scope 4
2 Normative references 4
3 Definitions, symbols and units 5
4 Input data for the calculations 7
5 Calculation of surface temperature to avoid critical surface humidity 10
6 Calculation of interstitial condensation 12
Annex A (informative) Classes of internal humidity load 21
Annex B (informative) Examples of calculation of the temperature factor at the internal surface to avoid
critical surface humidity 22
Annex C (informative) Examples of calculation of interstitial condensation 26
Annex D (informative) The assessment of the risk of condensation on window frames 31
Annex E (informative) Relationships governing moisture transfer and water vapour pressure 32
Annex F (informative) More advanced calculation methods 34
ANNEX ZA (normative) Normative references to international publications with their corresponding
European publications 35
ANNEX ZB (informative) Informative references to international publications with their corresponding
European publications 36
Page 3
Foreword
The text of EN ISO 13788:2001 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 insulation".
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 2002, and conflicting national
standards shall be withdrawn at the latest by January 2002.
This standard is one of a series of standards, which specify test methods for the thermal and
moisture related properties of building materials and products.
The European publications to be used instead of the International Standards listed in clause 2 are
given in normative annex ZA, which is an integral part of this European Standard.
The annexes A, B, C, D, E, F and ZB are informative. Annex ZA is normative.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United
Kingdom.
Introduction
Moisture transfer is a very complex process and the knowledge of moisture transfer mechanisms,
material properties, initial conditions and boundary conditions is often insufficient, inadequate
and still under development. Therefore this standard lays down simplified calculation methods,
based on experience and commonly accepted knowledge. The standardisation of these
calculation methods does not exclude use of more advanced methods. The calculations will
normally lead to designs well on the safe side and if a construction fails a specified design
criterion according to this procedure, more accurate methods may be used to show that the design
will pass.
This standard deals with critical surface humidity and interstitial condensation, and does not
cover other aspects of moisture, e.g. ground water, precipitation, built-in moisture and moisture
convection, which can be considered in the design of a building component.
Page 4
1Scope
This standard gives calculation methods for:
a) The internal surface temperature of a building component or building element below which
mould growth is likely, given the internal temperature and relative humidity – the method
can also be used to assess the risk of other surface condensation problems.
b) The assessment of the risk of interstitial condensation due to water vapour diffusion. The
method used assumes built-in water has dried out and does not take account of a number of
important physical phenomena including:
- the dependence of thermal conductivity on moisture content;
- the release and absorption of latent heat;
- the variation of material properties with moisture content;
- capillary suction and liquid moisture transfer within materials;
- air movement through cracks or within air spaces;
- the hygroscopic moisture capacity of materials.
Consequently the method is applicable only to structures where these effects are negligible.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies.
EN 12524 Building materials and products – Hygrothermal properties - Tabulated design
values
ISO 6946 Building components and building elements – Thermal resistance and thermal
transmittance - Calculation method
ISO 9346 Thermal insulation - Mass transfer - Physical quantities and definitions
ISO 10211-1 Thermal bridges in building construction – Calculation of heat flows and surface
temperatures - Part 1: General methods
ISO 10456 Building materials and products – Procedures for determining declared and
design thermal values
ISO 12572 Hygrothermal performance of building materials and products - Determination of
water vapour transmission properties
Page 5
ISO 15927-1 Hygrothermal performance of buildings – Calculation and presentation of
climatic data - Part 1: Monthly means of single meteorological elements
3 Definitions, symbols and units
3.1 Terms and definitions
For the purposes of this standard, the terms and definitions given in ISO 9346 and the following
apply.
3.1.1
temperature factor at the internal surface
difference between the temperature of the internal surface and the external air temperature,
divided by the difference between the internal air temperature and the external air temperature,
calculated with a surface resistance at the internal surface R :
si
si e
f (1)
Rsi
i e
Methods of calculating the temperature factor in complex constructions are given in
ISO 10211-1.
3.1.2
design temperature factor at the internal surface
minimum acceptable temperature factor at the internal surface:
si,min e
f (2)
Rsi,min
i e
3.1.3
minimum acceptable temperature
lowest internal surface temperature before mould growth starts
3.1.4
internal moisture excess
rate of moisture production in a space divided by the air change rate and the volume of the space:
v= v - v = G/(n V) (3)
i e
3.1.5
water vapour diffusion-equivalent air layer thickness
thickness of a motionless air layer which has the same water vapour resistance as the material
layer in question:
s = d (4)
d
3.1.6
relative humidity
ratio of the vapour pressure to the saturated vapour pressure at the same temperature:
p
(5)
p sat
To be published
Page 6
3.1.7
critical surface humidity
relative humidity at the surface that leads to deterioration of the surface, specifically mould
growth
3.2 Symbols and units
Symbol Quantity Unit
D water vapour diffusion coefficient in a material m /s
D water vapour diffusion coefficient in air m /s
G internal moisture production rate kg/h
M accumulated moisture content per area at an kg/m
a
interface
2.
R thermal resistance m K/W
. .
R gas constant for water vapour = 462 Pa m /(K kg)
v
T temperature K
.
U thermal transmittance of component or element W/(m K)
V internal volume of building m
2. .
Z water vapour resistance with respect to partial m s Pa/kg
p
vapour pressure
Z water vapour resistance with respect to humidity s/m
v
by volume
d material layer thickness m
f temperature factor at the internal surface -
Rsi
f design temperature factor at the internal surface -
Rsi,min
2.
g density of water vapour flow rate kg/(m s)
-1
n air change rate h
p water vapour pressure Pa
q density of heat flow rate W/m
s water vapour diffusion-equivalent air layer m
d
thickness
t time s
w moisture content mass by volume kg/m
. .
water vapour permeability of material with kg/(m s Pa)
p
respect to partial vapour pressure
. .
water vapour permeability of air with respect to kg/(m s Pa)0
partial vapour pressure
v humidity of air by volume kg/m
v internal moisture excess, v – v kg/m
i e
internal vapour pressure excess, p – p Pap
i e
relative humidity of air -
.
thermal conductivity W/(m K)
water vapour resistance factor -
Celsius temperatureC
minimum acceptable surface temperatureC
si,min
Page 7
3.3 Subscripts
c condensation n interface
cr critical value s surface
e external air sat value at saturation
ev evaporation se external surface
i internal air si internal surface
min minimum value T total over whole component or element
4 Input data for the calculations
4.1 Material and product properties
For the calculations, design values shall be used. Design values in product or material
specifications or the tabulated design values given in the standards referred to in Table 1 may be
used.
Table 1 - Material and product properties
Property Symbol Design values
Thermal conductivity Obtained from EN 12524 or determined in
thermal resistance accordance with ISO 10456.
R
Water vapour resistance factor Obtained from EN 12524 or determined in
water vapour diffusion-equivalent air accordance with ISO 12572.
s
d
layer thickness
Thermal conductivity, and water vapour resistance factor, , are applicable to homogenous
materials and thermal resistance, R, and water vapour diffusion-equivalent air layer thickness, s ,
d
primarily to composite products or products without well-defined thickness.
For air layers, R is taken from ISO 6946; s is assumed to be 0,01 m, independent of air layer
d
thickness and inclination.
4.2 Climatic conditions
4.2.1 Location
Unless otherwise specified, the external conditions used shall be representative of the location of
the building.
4.2.2 Time period
For the calculation of the risk of surface mould growth or the assessment of structures for the risk
of interstitial condensation, monthly mean values, derived using the methods described in
ISO 15927-1, shall be used.
For calculations of the risk of surface condensation on low thermal inertia elements such as, for
example, windows and their frames, the mean annual minimum temperature on a daily basis and
corresponding relative humidity shall be used.
Page 8
NOTE This implies that there will be some condensation on one day in half the years.
4.2.3 Temperatures
The following temperatures shall be used for the calculations.
a) External air temperature as specified in 4.2.2.
b) Ground temperature adjacent to building components.
The annual mean value of the external air temperature shall be used.
c) Internal air temperature.
Use values according to the expected use of the building. Internal air temperatures to be u
...
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