I have spent 30 years working in attics and I cant stand that spray in Radiant berrier. If you shine a light in an attic with that stuff you can see particles floating everywhere. Just nasty to breath. Best way to cool your attic off is too install extra soffets around your house and have a roofer install the tallest ridge vents that they make. Those are always the cooling attics I have ever worked in. If you are worried about energy savings spend 50 bucks on an infared temp gun and on a hot day measure the temp of an interior wall and your ceiling. If the temp is the same I would not do anything. If there is a huge temp diffence maybee you are missing attic insulation in that part of the house. Hope this helps.
@SwaggyG: When we replaced all of our exterior wood with Hardy plank, that included the soffit and fascia. The soffit contains numerous small holes all along it's length. It's much better than putting individual soffit vents on your house. However, if you're not planning to replace your soffit and fascia, then I agree that the more soffit vents, the better.
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