This is how to make passive solar heater for under $20 or so. It is basically a greenhouse box. Simple yet brilliant. It is environmentally friendly (after it is assembled), green, handy, forehead slappingly easy to make, and even an awesome project for shop class. Ok so it will not become school curriculum, but most agree it should be damn it! grumble government subsidies grumble greed and priorities and blah…watch this and learn!