Well, I'm stuck doing all this in a two-bedroom apartment, so fermentation is pretty much limited to the temperatures I want to live at. (The reason I haven't made beer before now is that I wanted to wait til I had a basement. Got sick of waiting.) I've taped over the vent to the spare bathroom to reduce the temperature fluctuation and I'll keep the thermostat steady, but that's about all I can do to control the temperature unless I also put water in the tub where I keep the fermenter. I've had a thermometer with a 24 hr high/low readout in the room for a few days and it's been staying between 68F and 70F. I can push it a little cooler and constantly wear sweaters, but that's about it.
Edited to add: Before you ask, it's an interior room with only incandescent lights.