BS EN 673:2011 pdf download.Glass in building – Determination of thermal transmittance (U value) – Calculation method.
BS EN 673 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 g4ass 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 If value of windows, doors and shutters (see EN ISO 10077-1 Ill) 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. L2J)
Reference shouid be made to (3], [4J and (51 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 wi EN 12898
The rules have been made as sample as possible consastent with accuracy.
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 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
EN 12898, Glass In building — Determrnation of the emissivity
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Ii value
parameter of glazing which characterizes the heat transfer through the central part of the glazing, ee. without edge effects, and states the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side
NOTE The U value Is given in watts per square metre Kelvin [Wl(m2K)].
3.2 declared value
U value obtained under standardized boundary conditions (see Clause 8).BS EN 673 pdf download.
BS EN 673:2011 pdf download
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