CEN/TC 129/WG 9 - Light and energy transmission, thermal insulation

This document specifies a calculation method to determine the thermal transmittance of glass with flat and parallel surfaces.
This document 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, glass ceramic, alkaline earth silicate glass and alumino silicate glass. 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 document determines the U value (thermal transmittance) in the central area of glazing.
The edge effects due to the thermal bridge through the spacer of an insulating glass 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 document.
NOTE   EN ISO 10077 1:2017 provides a methodology for calculating the overall U value of windows, doors and shutters [1], taking account of the U value calculated for the glass components according to this document.
Also excluded from the calculation methodology are any effects due to gases that absorb infrared radiation in the 5 to 50 µm range.
The primary purpose of this document is product comparison, for which 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 glass;
-   conduction heat gains in summer;
-   condensation on glass surfaces;
-   the effect of the absorbed solar radiation in determining the solar factor [2].
Reference can 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.
Reference can be made to [6] for detailed calculations of U values of glazing, including shading devices.
Vacuum Insulating Glass (VIG) is excluded from the scope of this document. For determination of the U value of VIG, please refer to EN 674 or ISO 19916-1.
A procedure for the determination of emissivity is given in EN 12898.
The rules have been made as simple as possible consistent with accuracy.

This standard provides a procedure to validate a calculation tool of spectrophotometric and thermal characteristics of the glass products following EN 410 or EN 673. It provides also the methodology to correctly use measured data in the calculation tool.  
The following characteristics are included in the scope of this standard:
- light transmittance (tv)
- light reflectance - both sides (rv, r'v)
- solar direct transmittance (te)
- solar direct reflectance – both sides (re, r'e)
- total solar energy transmittance (solar factor or g value) (g)
- thermal transmittance (U value) in the vertical position
The following characteristics are excluded from the scope of this standard:
- UV transmittance (tuv)
- shading coefficient (SC)
- general colour rendering index (Ra)
- thermal transmittance (U value) at angles other than vertical

This document specifies a procedure for determining the emissivity at room temperature of the surfaces of glass and coated glass.
The emissivity is necessary for taking into account heat transfer by radiation from surfaces at the standard temperature of 283 K in the determination of the U value and of the total solar transmittance of glazing according to [1] to [4].
The procedure, being based on spectrophotometric regular reflectance measurements at near normal incidence on materials that are non-transparent in the infrared region, is not applicable to glazing components with at least one of the following characteristics:
a) with rough or structured surfaces where the incident radiation is diffusely reflected;
b) with curved surfaces where the incident radiation is regularly reflected at angles unsuitable to reach the detector while using regular reflectance accessories;
c) infrared transparent.
However, it can be applied with caution to any glazing component provided its surfaces are flat and non-diffusing (see 3.6) and it is non-transparent in the infrared region (see 3.7).
Although transmittance measurements are included in this document, they are only necessary to check if the sample is non-transparent in the infrared region in the context of this document (see 3.7). If the sample is transparent in the infrared region, this document is not applicable.
The previous version of this document was based on the use of reflectance measurements using double beam dispersive infrared spectrophotometers capable of measuring over almost the entire spectral range of a black body at the standard reference temperature and determining the emissivity by the 30 ordinate method [6]. This version takes account of Fourier Transform Infrared (FTIR) spectrophotometers where the spectral range is limited. It describes a method whereby spectrophotometers can be used to determine emissivity if they are able to measure up to the 24th ordinate point and if they satisfy a noise criterion for this spectral range. It allows the inclusion of data from the 25th ordinate point up to the 30th ordinate point. A new informative annex (Annex D) describing the principles of absolute reflection accessories has been added to this version. These accessories are intended to be used by qualified personnel.
As FTIR spectrophotometers are single beam instruments as opposed to dispersive spectrophotometers which are double beam instruments (and thus able to correct for instrument drift), a procedure was developed by the European funded project, THERMES, to correct for drift. This procedure is described in [10] and [16]. Other categories of ordinate errors using FTIR spectrophotometers are discussed in [14].

This European Standard specifies a measurement method to determine the thermal transmittance of glazing with flat and parallel surfaces. Structured surfaces, e.g. patterned glass, can be considered to be flat.
This European Standard applies to multiple glazing with outer panes which are not transparent to far infrared radiation, which is the case for soda lime silicate glass products, borosilicate glass and glass ceramics. Internal elements may be far infrared transparent.
The procedure specified in this European Standard determines the U value ) (thermal transmittance) in the central area of glazing. The edge effects, due to the thermal bridge through the spacer of an insulating glass unit or through the window frame are not included. Furthermore energy transfer due to solar radiation is not taken into account.
The procedure specified in this European Standard should generally only be considered when the calculation method detailed in EN 673 is inappropriate or unsuitable.
The document for the calculation of the overall U value of windows, doors and shutters (see [3]) gives normative reference to the U value evaluated for the glazing components according to this standard.
A vertical position of the glazing is specified.
U values evaluated according to the present standard are used for product comparison as well as for other purposes, in particular for predicting:
-   heat loss through glazing;
-   conduction heat gains in summer;
-   condensation on glazing surfaces;
-   the effects of the absorbed solar radiation in determining the solar factor (see [1]).
Reference should be made to [4], [5], or other European Standards dealing with heat loss calculations for the application of glazing U values determined by this standard.
The determination of the thermal transmittance is performed for conditions which correspond to the average situation for glazing in practice.

This European Standard specifies a measurement procedure to determine the thermal transmittance of glazing with flat and parallel surfaces. For the purpose of this Standard, structured surfaces may be considered to be flat..
This European Standard applies to multiple glazing with outer panes which are not transparent to far infrared radiation (in the wavelength range 5 to 50μm), which is the case for soda lime silicate glass products, borosilicate glass and glass ceramics. Internal elements can be far infrared transparent.
The procedure specified in this European Standard determines the U value (thermal transmittance) in the central area of glazing. The edge effects due to the thermal bridge through the spacer of an insulating glass unit or through the window frame are not included.
The edge effects due to the thermal bridge through the spacer of an insulating glass unit or through the window frame are excluded.  Energy transfer due to solar radiation is also excluded.
The procedure specified in this European Standard should be considered only when the thermal transmittance of the glazing cannot be calculated in accordance with EN 673.
The determination of the thermal transmittance is performed for conditions which correspond to the average situation for glazing in practice.
NOTE   Patterned glass is an example of a glass with a structured surface;
For the purposes of product comparison, a vertical position of the glazing is specified (see Clause 10).
U values evaluated according to the present standard are used for product comparison as well as for other purposes, in particular for predicting:
- heat loss through glazing;
- conduction heat gains in summer;
- condensation on glazing surfaces;
- the effects of the absorbed solar radiation in determining the solar factor (see A.2).
Reference should be made to A.3, A.4, A.5 or other European Standards dealing with heat loss calculations for the application of glazing U values determined by this Standard.
The determination of the thermal transmittance is performed for conditions which correspond to the average situation for glazing in practice.
NOTE   Patterned glass is an example of a glass with a structured surface;

This European Standard specifies methods of determining the luminous and solar characteristics of glazing in buildings. These characteristic can serve as a basis for lighting, heating and cooling calculations of rooms and permit comparison between different types of glazing.
This European Standard applies both to conventional glazing and to absorbing or reflecting solar-control glazing, used as vertical or horizontal glazed apertures. The appropriate formulae for single, double and triple glazing are given.
This European Standard is accordingly applicable to all transparent materials except those which show significant transmission in the wavelength region 5 µm to 50 µm of ambient temperature radiation, such as certain plastic materials.
Materials with light-scattering properties for incident radiation are dealt with as conventional transparent materials subject to certain conditions (see 5.2).
Angular light and solar properties of glass in building are excluded from this Standard. However, research work in this area is summarised in E.1, E.2 and E.3.
While this European Standard presents the formulae for the exact calculations of the spectral characteristics of glazing, it does not consider the uncertainty of the measurements necessary to determine the spectral parameters that are used in the calculations. It should be noted that, for simple glazing systems where few measurements are required, the uncertainty of the results will be satisfactory if correct measurements procedures have been followed. When the glazing systems become complex and a large number of measurements are required to determine the spectral parameters, the uncertainty is cumulative with the number of measurements and should be considered in the final results.
The term interface used in this European Standard, is considered to be a surface characterized by its transmission and reflections of light intensities.

This European Standard specifies a calculation method to determine the energy balance value of glazing. This
European Standard applies to transparent materials such as glass and combinations of glass used to glaze
windows in buildings.
This method is intended to evaluate the balance of heat loss and useful heat gain by solar radiation entering the
building through the glazing for a given period by means of an average rate of loss (or gain) of heat called the
energy balance value.
The method enables producers to compare the performance of their glazing products. The energy balance value
should not be used for energy use or heating capacity calculations in buildings.

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 value ) (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 A.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 Clause 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.
The rules have been made as simple as possible consistent with accuracy.

This draft European Standard specifies a procedure for determining the emissivity at room temperature of the surfaces of glass, coated glass and other glazing components not transparent in the far infrared. The emissivity is necessary for taking into account heat transfer by radiation from surfaces at the standard temperature of 283 K in the determination of the U value and of the total solar transmittance of glazing according to B.1 to B.5.

This European Standard specifies a measurement method to determine the thermal transmittance of glazing with flat and parallel surfaces. Structured surfaces, e.g. patterned glass, can be considered to be flat. This European Standard applies to multiple glazing with outer panes which are not transparent to far infrared radiation, which is the case for soda lime glass products, borosilicate glass and glass ceramics. Internal elements may be far infrared transparent.

This European Standard specifies a measuremnet procedure used to determine the thermal transmittance of glazing with flat and parallel surfaces. Structured surfaces, e.g. patterned glass, may be considered to be flat. This European Standard applies to multiple glazing with outer panes which are not transparent to far infrared radiation, which is the case for soda lime glass products, borosilicate glass and glass ceramics. Internal elements can be far infrared transparent.

Changed from ENQ+FV to UAP (CC/011211)

This European Standard specifies methods of determining the luminous and solar characteristics of glazing in buildings. These characteristic can serve as a basis for lighting, heating and cooling calculations of rooms and permit comparison between different types of glazing.  This European Standard applies both to conventional glazing and to absorbing or reflecting solar-control glazing, used as vertical or horizontal glazed apertures. The appropriate formulae for single, double and triple glazing are given.

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.

This European standard specifies a calculation method to determine the thermal transmittance of glazing with flat and parallel surfaces. This amendment corresponds to the introduction of Xenon gas data.