[j12piprius]

Insulation doesn't keep heat from getting in, but absorbs it, then releases the heat into the house through the night. The result is that the house stays hot and uncomfortable through the night.

A much better alternative is radiant barrier foil, stapled to the rafters. It is inexpensive, quick and easy to install on one's own. When the temp was 112 here a few years ago, the house got up to a comfortable 83 inside, but is usually in the mid 70's in the summers, and I never use any a/c.

Another advantage is the foil reflects internal heat back into the house in the winters, keeping the house cooler in summers, and warmer in winters. I only had heat from the fireplace insert 7 times last winter, compared to 45 times a few years ago.