[FONT=comic sans ms,sand]All this is is cutting a hole in the wall then boxing it painting the inside black and covering the outside with glass. Then leave openings at the bottom and top of the box for circulation. Cold air as it enters the bottom is heated and rises. As it rises it pulls more cold air into the bottom. There you have it Passive solar heating. I read about this in the Mother Earth News.[/FONT]

Cutting the hole. I took the sheathing and nailed it inside.
and I'm painting it black.
Notice the glass to cover out side after I finish painting. There are 1/2" slits at the bottom and top for air circulation and that's it. During the summer I'll cover it.

This is the finished product, not to shabby. We plan to replace the doors with a regular door.The shed is south facing so we'll build to more elements on either side of it.I don't know how much heat they will generate in the winter, but it's free so it's worth the effort.