Reflective Coating on Flat Roof

Hmm.

A cheap shot would be to simply paint the roof white and see if that made much of a difference. I suspect it will.

Think more about a coating rather than a covering. Metal slabs, for instance, might allow water to be trapped between the covering and the original roof.

You can get 5-gallon buckets of roof aluminizer at Home Depot or similar places.

Bruce K. wrote the following:

From this site:

"Solar reflectance isn't the only property to look for in a roofing material. It should also have a high infrared emittance to help the roof shed heat by re-radiation. Most materials do with the notable exception of aluminum roof coatings. Aluminum will stay warmer at night, while a white roof coating will radiate more of its stored heat back to the sky. For this reason, aluminum will not perform quite as well as a white material with a similar solar reflectance.Solar reflectance isn't the only property to look for in a roofing material. It should also have a high infrared emittance to help the roof shed heat by re-radiation. Most materials do with the notable exception of aluminum roof coatings. Aluminum will stay warmer at night, while a white roof coating will radiate more of its stored heat back to the sky. For this reason, aluminum will not perform quite as well as a white material with a similar solar reflectance".

I painted my Sunroom's black shingle roof with a white roof paint by Henry. Made a considerable difference in the room temperature below.

willshak wrote the following:

Sorry, I double pasted the quote from the site.