Cheap way to help keep your house cool in the summer heat.
In the summer, I put cheap reflective Mylar emergency blankets on windows and sliding glass doors that get full direct sun. I use a spray bottle to mist water on the glass, place the blanket on the glass, smooth it out, and then a likely clear tap on the edges. It cost less then a $1 per window and significantly cuts my energy bill.
I'll take it down in the fall because I want the full sun to help heat the house.