So I get a few months out of the year here that I can ferment at good temps either in my house or in my garage. I hate doing it in my house because there isn't much room and it often gets messy. My garage is freezing cold 6 months out of the year, and extremely hot for a few months in the summer. So I needed a fermentation chamber.
I used some foam insulation board from my local building supply, an ebay temperature controller, and a small cheap heater. I haven't finished the build, I'm going to enclose it with plywood, and when I come across a cheap enough mini fridge I'll gut it for cooling. So far this has been keeping my fermenting beer at 68 degrees pretty consistently. Here's some pictures.
The box was $10 at home depot and I wired up outlets on either side. This side is for heating. The other side is for cooling.
The space heater was $10 at home depot and works great. Once the beer is up to the right temp it hardly ever turns on.
I can fit two buckets (or carboys) in the chamber, and I'll probably expand the chamber a bit so I can fit the heater and the cooling elements inside with two vessels fermenting.
I have a lot of work still to get it where I want, but this is a good start (functioning anyway). I'll update with more pics as I go.