I have done them in the attic for years and had little problems, I am now trying it in house and have had a crazy amount of problems, just use a heater on a timer when the lights are off. You should not have a problem with the temp when the lights are on as it is winter here in the uk now. There will always be a chance the helicopter will see you but that is the risk you take. Oh and just remember the risk of snow, you don't want to be the only house on the block with no snow on the roof. If you need any more info just ask and I hope the helps.