Absorbance Values

Heat reflective paints, or solar reflective paint, used during the roof restoration process of a cement tiled or metal roof must be independentley tested for solar absorbance.  Each individual colour specified as a solar reflective colour for roof restoration is indiviually tested to provide a solar absorbance value.  This value is the amount of solar energy that is absorbed by a substrate and is expressed as a value in percent from 0 to 100.  100 being the highest absorbance, (hot).  0 being the lowest absorbance, (cool). 

 

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Solar Absorbance of Energy Star Heat Reflective Paints 

Independent Testing - Solar Absorbance (Abs)

Solar absorbance is the amount of solar energy (visible, infrared and ultraviolet), that is absorbed by a substrate and is expressed as a value in percent from 0 to 100.

100 being the highest absorbance, (hot).

0 being the lowest absorbance, (cool).

When sunlight strikes a building envelope, solar energy is either absorbed by the substrate or reflected away from it. The type of substrate causes varying absorbance results which are expressed as a percent and is the amount of solar energy that the substrate retains.

Energy Star coatings have the ability to reduce the absorbance value of all construction surfaces to values as low as 0.097.

To put the measure of an absorbance value into clear perspective, below is an example of what is achieved by reducing the absorbance of plain galvanised metal roofing. The temperature values stated are based on a day with a temperature of 37 deg C.

Plain galvanised metal roofing
Abs 0.327
Substrate temperate @ 37 deg C                                            80 deg C

Energy Star coated galvanised metal roofing
Abs 0.097
Substrate temperate @ 37 deg C                                            41 deg C

Difference in substrate temperature                                      39 deg C