Recently there was a discussion on a tree planting forum. Contractors in the field will put a tarp over boxes of seedlings to keep them cool. The tarp is white on one side, and aluminum coated mylar on the other. Discussion was: * do these work? * Silver side in or out? Whether white or aluminum, I don't see that it makes much difference. The ideal material would be perfectly white with an emissivity of close to zero. Whether is is white (random scattering) or silver (specularly reflecting) makes little difference.