So long as it doesn't melt, if it will reflect visable light, it will reflect heat, unless we get into some exotic materials.

My concerns are more rain and wind durability. Sure, a gentle breeze they can do, but can they handle small hail? 40mph gusts? Uncommon, but it's on my mind today- I got almost half an inch of rain with a little hail in an hour today, I'd estimate the winds at peak at having been around 35-40.