I'm thinking of adding a ceiling to my porch to create an insulation space (the roof alone radiates a lot of direct heat in the summer; the porch otherwise is open) between it and the roof (corrugated fiberglass) but I'd like to still be able to see the roof as I've already painted the roof's interior and like how it contrasts with the supporting frame's color.I'm also looking to paint the exterior of the roof to better waterproof it (some leaks where previous owner screwed it in) and to better reflect light to further reduce heat. Any suggestion on paint or would it be better to just replace the roof entirely with better material? Thanks!
There are many ways you could go. Yes, you can use the plexi to create insulation space. The best insulation is dead air. That is, air that cannot circulate and move around. The key to using it will be using something to seal it tight, a clear silicone caulk, perhaps. They make a special glue for it, you could make smaller areas to help keep air movement down with strips inside the ceiling area to form the pockets of air. Think bubblewrap, only solid. Probably caulk or glue on the joists is good enough. As for the exterior, fiberglass is extremely difficult to get paint to stick to, unless you use the gel coat stuff made for it. Maybe there is a good primer to make it take paints. If possible, paint it with the same stuff made for mobile home roofs, tho I don't know how well it will stick to fiberglass, it does fine on the metal roof of a mobile home. The stuff I'm talking about is available in only a few colors, white, silver, gray, and black. It's thick, like tar, but not tar. If you use the silver or white, it should help keep down the heat, after all, that's what it's designed for. It also has insulation and leak sealing properties. If you have a good cheap supply of the plexi, you could also put plexi over it for sealing, but before you do, you could use window tint on it, the kind that looks like a mirror on one side, and is dark on the other. put the mirror towards the sun. If you put your mind to it, there are probably many many ways to get done what you need to do. Maybe there's some way to use recycled materials.
You can many ways could go.