I am doing this as we speak. I had the house well insulated and so now instead of using 3 bitcoin miners to keep the uninsulated house warm, I now only use one. The lowest I think was about 46 F but even though I hate spending money on the electricity bill. It has not been too cold here but it makes me feel better that the energy being used is not being completely wasted.
There is a backup heater on standby just in case the temperature drops too low. I guess I could set up a thermostat to turn additional miners on and off as needed but I do not think the mining pools would be too happy with that.
By the way, I am not earning too much since my miner is just an old S1 180 Gh/s unit but something is something.