"3) Looking at previous posts, there seems to be some confusion about the difference between reflectivity and emissivity. A "cool roof" pigment should have be high in both, i.e., it should reflect incoming radiation, as well as emit long-wave radiation when it's hot."
Joe is correct. The relationship that emissivity = 1 - reflectivity is a simplified concept, but is close enough for most materials. Also when this relationship deviates somewhat, that deviation is usually not large (at the wavelength in question)...
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On 12.07.2014, at 03:09, "Joe Huang YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
3) Looking at previous posts, there seems to be some confusion about the difference between reflectivity and emissivity. A "cool roof" pigment should have be high in both, i.e., it should reflect incoming radiation, as well as emit long-wave radiation when it's hot.
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