Not too long ago, there was another thread about ceramic roof products. Bartley Heath has done some research on roof temperatures and found the following: Bare aluminum skin has the same reflectivity as black. With an outside temperature of 90 deg F, the skin temp was about double the ambient temperature. By applying a white paint, these temperatures dropped ~50 deg F.

I've painted a few trailers' roofs, steel and aluminum, with marine paints. Like Bartley, I have found the inside temps easily dropped ~15 deg F. These paints can be the basis for a DIY project at a fraction of the quoted ceramic costs. According to one pleased ceramic owner, you can realize the same inside temperature reduction with paint and a roller.

To coat a roof, it should be first washed and cleaned of all contaminates. Then depending on the paint's manufacturer, an approved primer is applied. The paint I use is a single part polyurethane, that can be sprayed, rolled or brushed on. It has a good flow rate that results in a smooth, high gloss finish. On a hot day, to prevent the paint from flashing too quickly, a reducer should be added to the paint, to prevent it from drying too soon.