Grouping of colors

Sandwich panels consist of three layers such as external sheet, insulation core and internal sheet. Due to physical properties of these layers, Sandwich panels are open to the harmful effects caused by different indoor and outdoor temperatures in terms of thermal expansion and rigidity. Steel, forms the outer and ınner surface of panel, has a higher expansion and shrinkage values than insulation core under the temperature. And because the steel is joined with the back coat to the core insulation and has different expansion properties, layers can be seperated, ondulation can be seen as bubbles and bulges when the limit values exceed under high temperature.

Light coloured panels stresses do not reach limit values while the dark and very dark colours influence must be taken into account and added up to the calculation of permanent and variable loads (panel dead load, structural loading, wind and snow load, etc.) Another harmful effect results from the fact that sandwich panels always operate between two environments with different temperatures. Normally, indoor temperature is above zero (+20°C) while the outside temperature is sub-zero (-30°C). Quite opposite conditions may occur in the case of freezers where indoor temperature may reach even -40°C while outdoors +30°C. As a result, external and internal surfaces behave differently -
cold surface shrinks while warm lining expands, which causes bending of the entire panel.

In order to assess the influence of thermal loads on the panels, all available colours have been divided into three brightness groups, based on the degree of heat absorption.

According to the EN 14509:2013 standard, the temperature of external lining (T1) reaches maximum value in summer, and depends on the colour and the degree of reflection of the surface. The T1 values that are minimum values for load capacity calculations and sufficient for calculating limit conditions of use are as follows:
Very light colours RG = 75-90% T OUT = +55ºC
Light colours RG = 40-74% T OUT = +65ºC
Dark colours RG= 8-39% T OUT = +80ºC
Where RG is the reflection grade in relation to magnesium oxide (100%)

As you can see from the values dark coloured panels expose to thermal load compared to light coloured panels. Due to light coloured panels, dark coloured panels have higher risk of fading, abrasion, colour gradation and ondulation risk.