I’ve had the idea for a while to paint my roof with white latex paint. I thought it might keep my roof from shedding (it’s got those shingles you see that are like tar paper with gravel on it - I don’t know what you call them), and that the white color might help keep my attic a few degress cooler in the summer time. Is there a reason this might be a bad idea, and do you think it really would prevent shedding/keep the attic cooler?
A lighter color will help reflect sunlight, sure.
But do you have a paint in mind that will stick to asphalt and gravel with minimal weathering? What happens when it starts to peel and the roof looks like hell? How much will this paint cost compared to a new layer of light-colored shingles?
Your current roof won’t last forever, anyway. Try replacing them with light-colored shingles when it’s time.
There are paint systems designed for asphalt roofs. You may want to make sure you add a fungicide to prevent discoloration.
This article on Painting the Town White and Green suggests biggest gains from painting. (The green refers to planting trees.)
Glidden sells a laytex roof treatment designed to replace roofing tar. It is snow white and lighter than tar and does not require all the heat to prepare. It has an RH of well over 40 from what I understand and is therefore great for commercial use (places that have to heat or AC all year round.).
I’m pretty sure I have only seen it used on flat roofs because it needs to be spread in a manner similar to tar and then has to set up between applications.
Maybe a big fan in the attic that directs air outside would keep things cooler?
I have trouble just getting latex paint to stick to the trim to my house. Any paint surface facing up gets 1/4 the life of a vertical surface. That means that regular latex paint that would last 10 years on a wall will be flaking off after 2 years on a ledge.