I use a fridge in my garage (right now it's about 15º, so it's not cooling anything!) with a small cube heater. The fridge is well insulated so the little heater can easily keep temp. I use a 2 stage Ranco controller, so I can have the fridge plugged in as well as the heater, and the controller gives heat or cold as necessary. The temp probe is in a stainless thermowell that is in the wort, so I am controlling fermentation temps, not ambient.