I've been running searches and I can't find this particular issue addressed. I see many many fermentation chambers and I've been looking at making one or two. One for lagering and one for ales. And I was wondering if anyone has attempted using radiant heat systems like used in flooring/walls. It strikes me as a perfect system especially if you already have the equipment installed in your house. Have your insulated chambers and the water coils around it mixed with some sort of dissipating material would remain a fairly constant temperature with little maintenance. Since the capacity to retain heat is several orders of magnitude higher in water than in air it would be rather energy efficient (say if I'm at my cabin or off the grid and were using solar panels) and be easily adjustable and stable. Just my thoughts. If you can throw a design at me or posts I'd love to do some research. If not I may be doing some tinkering this weekend.