If the sun beating on your windows this summer is baking the place—or just making your air conditioner work harder—you can hang material that blocks the heat in your windows. Do-it-yourselfer thenickboy says: To save electricity with our super expensive A/C, I constructed reflective curtains to block sunlight from warming our house. Think auto windshield. This is super simple and kind of obvious, but it works well. Basically he hung foam, reflective material that windshield blockers are made of as curtains. Along similar lines, home blogger Emily Gertz did the same using foam and aluminum foil. Beat the Heat for Cheap: Reflective panels for your windows [Apartment Ecology via Make]Heat blocking curtains [Instructables via Make]