I've been looking at heat pump water heaters
and it got me to thinking...
This thing works by taking heat from the air and putting it into your water, so it pumps out cool air. Supposed to save you money over a regular water heater. Might you be able to harness the cold air output for a fermentation chamber?
Not only are you not paying for cooling for your chamber, but you're paying less to heat your water!
The only question would be how to regulate the temp of the chamber. I was thinking about a thermostat controlled fan that would add warmer air to the chamber when it gets too cold or something like that.
I don't think you would be able to seal the chamber since the back pressure might interfere with the heat pump, but a few small holes on the top of the chamber should let the pressure out and keep the cold in.