I have also considered buying big rolls of that aluminum-bubble-wrap-type stuff they use in car windshields.

Think how well that would reflect heat back... keep the house nice and cool.

If we didn't have electricity for extended periods... I would set up a tent in my backyard. It would be much cooler than in a house.

It is amazing how cool you can get by just laying on the ground. It might be hard as a rock, but it really cools you down. I would save the inside for rainy nights and winter.