It isn't a shed, its a garage.

This has been coming for a long time, but I would be fibbing if the jeep project didn't speed up my progress. I decided to try out some ideas with this project that I would one day like to use in a house. I like the idea of thermal mass and passive solar heat, so I insulated my concrete slab with rigid polystyrene and ran 1/2" pex tubing for in floor radiant heating. To passively heat the slab I placed my roof trusses such that they have a southern exposure. With the addition of three skylights, two straight through for direct sunlight and one into a hot box with a water cylinder painted black, I will use sunlight to brighten and heat the slab through green house affect and passively heating water that will circulate through the slab. I will put in a small hot water boiler in series with the system as back up heat, and the water will have a 20% Etheline Glycol additive for freeze protection. Having the solar collector in the rafters necessitates a pump to circulate the water, since its the reverse orientation for thermo siphoning to work for me. However I intend to use a small 12v pump with a solar cell. The pump doesn't have to do much work, as the system is balanced in terms of head; the only work the pump has to do is overcome the friction of the pipes and the difference in weight of hot vs cool water. Also, I only want the circulation to happen during the day, I don't want cool water circulated through my warmed up slab at night, a solar powered pump would be pretty good at circulating only when heat transfer is needed.