EN 673:2011

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.PHWRGDGlas im Bauwesen - Bestimmung des U-Wertes (Wärmedurchgangskoeffizient) - BerechnungsverfahrenVerre dans la construction - Détermination du coefficient de transmission thermique, U - Méthode de calculGlass in building - Determination of thermal transmittance (U value) - Calculation method81.040.20Steklo v gradbeništvuGlass in buildingICS:Ta slovenski standard je istoveten z:EN 673:2011SIST EN 673:2011en,fr,de01-maj-2011SIST EN 673:2011SLOVENSKI
STANDARDSIST EN 673:1999/A2:2004SIST EN 673:1999/A1:2001SIST EN 673:19991DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 673
February 2011 ICS 81.040.20 Supersedes EN 673:1997English Version
Glass in building - Determination of thermal transmittance (U value) - Calculation method
Verre dans la construction - Détermination du coefficient de transmission thermique, U - Méthode de calcul
Glas im Bauwesen - Bestimmung des U-Werts (Wärmedurchgangskoeffizient) - Berechnungsverfahren This European Standard was approved by CEN on 2 January 2011.
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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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B-1000 Brussels © 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 673:2011: ESIST EN 673:2011

Iteration procedure for glazing with more than one gas space . 16Bibliography . 18 SIST EN 673:2011

This European Standard specifies a calculation method to determine the thermal transmittance of glazing with flat and parallel surfaces. This European Standard applies to uncoated glass (including glass with structured surfaces, e.g. patterned glass), coated glass and materials not transparent in the far infrared which is the case for soda lime glass products, borosilicate glass and glass ceramic. It applies also to multiple glazing comprising such glasses and/or materials. It does not apply to multiple glazing which include in the gas space sheets or foils that are far infrared transparent. The procedure specified in this European Standard determines the U value1) (thermal transmittance) in the central area of glazing. The edge effects due to the thermal bridge through the spacer of a sealed glazing unit or through the window frame are not included. Furthermore, energy transfer due to solar radiation is not taken into account. The effects of Georgian and other bars are excluded from the scope of this European Standard. The standard for the calculation of the overall U value of windows, doors and shutters (see EN ISO 10077-1 [1]) gives normative reference to the U value calculated for the glazing components according to this standard. For the purpose of product comparison, a vertical position of the glazing is specified. In addition, U values are calculated using the same procedure for other purposes, in particular for predicting:  heat loss through glazing;  conduction heat gains in summer;  condensation on glazing surfaces;  the effect of the absorbed solar radiation in determining the solar factor (see Bibliography, [2]). Reference should be made to [3], [4] and [5] or other European Standards dealing with heat loss calculations for the application of glazing U values determined by this standard. A procedure for the determination of emissivity is given in EN 12898.
1) In some countries the symbol k has been used hitherto.
A
constant
-
c
specific heat capacity of gas
J/(kg⋅K)
d
thickness of material layer (glass
or alternative glazing material)
m
F
volume fraction
-
h
- heat transfer coefficient
W/(m2⋅K)
- also thermal conductance
W/(m2⋅K)
M
number of material layers
-
n
exponent
-
N
number of spaces
- SIST EN 673:2011
r
thermal resistivity of glass (glazing material)
m⋅K/W
P
gas property
-
s
width of gas space
m
T
absolute temperature
K
U
thermal transmittance
W/(m2⋅K)
∆Τ temperature difference
K
ε
corrected emissivity
-
εn
normal emissivity (perpendicular to the surface)
-
ρ
gas density
kg/m3
σ
Stefan-Boltzmann's constant 5,67 x 10-8
W/(m2⋅K4)
µ
dynamic viscosity of gas
kg/(m⋅s)
λ
- thermal conductivity of gas in space
W/(m⋅K)
ϑ
temperature on the Celsius scale
°C 4.2 Dimensionless Numbers
Gr
Grashof number
-
Nu
Nusselt number
-
Pr
Prandtl number
- 4.3 Subscripts
c
convection
e
external
i
internal
j
jth material layer
k
kth space
g
gas
m
mean
n
normal
r
radiation
s
space SIST EN 673:2011
t
total
1;2
first, second etc. 5 Basic formulae 5.1 General The method of this standard is based on a calculation according to the following principles. 5.2 U value The U value is given by: 1U=1he+1ht+1hi (1) where
he and hi are the external and internal heat transfer coefficients;
ht is the total thermal conductance of the glazing. 1ht=1hs1N∑+dj1M∑⋅rj (2) where
hs is the thermal conductance of each gas space;
N is the number of spaces;
dj is the thickness of each material layer;
rj is the thermal res
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