Optical tolerances

Light permeability:

For insulating glass with and without the use of coated surfaces, the light permeability depends significantly on the thickness of the individual panes used. The data provided in the tables for the light permeability of insulating glass apply to individual glass thicknesses of 4 mm each for thermal insulating glass and 6 or 4 mm for solar protection glass. The percentages include a tolerance of ± 2 percentage points.

Total energy transmittance

The total energy transmittance (g-value) of insulating glass depends essentially on the thickness of the individual panes used. This applies in particular to the thickness of the outer pane. There are building regulations in Germany for the determination of the total energy transmittance of multi-pane insulating glass depending on the glass thickness. The data for the total energy transmittance of ISOLAR glass given in the tables refer to individual glass thicknesses of 4 mm each (thermal insulating glass, sound insulating glass) and 6 or 4 mm (solar protection glass), in each case in conjunction with the building regulations. The percentages include a tolerance of ± 2 percentage points.

Intrinsic colour

All materials used in glass products have their own raw material colours, which can be more pronounced with increasing thickness of the glass product. In order to meet the legal requirements with regard to energy saving, coated glasses are used. Even coated glasses have a natural colour. This intrinsic colour can be seen differently when looking through it and/or looking at it. Variations in the colour impression are possible and unavoidable due to the iron oxide content of the glass, the coating process, the coating itself as well as changes in the glass thicknesses and the pane structure.

Colour impression

The colour impression of insulating glass can also be described with the help of physical characteristics. The reflection colours are characterised by viewing from the outside and when viewing from the inside, as well as the colours when looking through from the outside to the inside and from the inside to the outside. In the case of all four colour impressions to be mentioned, the physical perception as well as the subjective perception of the human eye are of importance. The latter is also heavily dependent on the influences dominated by the respective light and/or lighting conditions. All the aforementioned colour impressions are subject to the fluctuations which are possible in ongoing production. Absolute colour uniformity is therefore not always possible, especially with coated glasses. In particular, colour deviations can not be ruled out when using coated glasses of different origin in the same building as well as for subsequent deliveries and retrofitting of insulating glass with coated surfaces.

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