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I built two of these last year for my house and hooked up a small solar fan at the top to blow the hot air into my living room and back room. I put a dryer vent fan over the inside so cold air doesn't blow into my house at night.
It raises the air temp in those two rooms almost 20 degrees F on sunny winter days.
I built mine out of 1x4's, 1" thick styrofoam sheets covered in dollar store aluminum foil, double layer of black aluminum window screen, and used plexiglass / lexan instead of glass because I was worried about icicles falling on it and shattering it. IIRC, it cost about $40 to build one. This year, I'm building a much bigger version to go over the window to my bedroom.
I highly recommend them as space heaters if you have south facing sunlight at all. They're removable so you don't have to worry about them heating up your space in summer.
-Spooky