Covering our roofs with it would certainly make a difference. BUT, it works in the winter too, cooling the house when we want it warm. So, that might be a problem for the comfort of the building.

Personally, I’m waiting for a commercial product, because my NM house has a large, south-facing stucco wall that is currently white, but not ultra cool white. Given my experience with the house, which is well insulated, I expect I could paint the house with such paint and not need any other cooling, even when it hits 100+F here. That wall is my bedroom wall, and I can feel the heat pushing through it in the late afternoon after a full day of exposure to the sun.