In an effort to make the greenhouse self sustainable, I have a flurry of things flying through my head for heating the greenhouse in the winter. One of these things is using a compost bin and put a coiled pipe inside filled with water, then do in-floor heat.

The only thing that I'm wondering is how often I would need to turn the compost over. I've been doing some reading, and some people are saying that the only reason you need to turn your pile is to get oxygen in the middle so that it starts the process over, and to get around this, some people have drilled holes in a pvc pipe to get oxygen to the center without the need to turn it over.

How feasible does all this sound? The greenhouse will be roughly 1000 cubic feet on the inside, with limited insulation (obviously). Any other ideas for heating the greenhouse without spending a fortune?