Mines in a tiny back room with no windows. It's handy for candling if you can make it really dark it's easier to see what's inside. Reasonably constant temperature will probably give the best results. The main fear is if it heats up quickly or too much (next to radiator, room with a fire, sun through windows, etc,) the thermostat cut the heat input, but this may not be enough to counteract the external heat. I'd put them in them in the snug.
Temp and humidity changes lot in my living room where i both dry washing and have a wood stove. I wouldn't want to hatch in here.
Was trying to think of other things.... My cat started sleeping on mine when I had it in the hall - kept altering the air vents! One other thing I read on a forum, was someone who lost all their chicks, all killed as hatching by their cat that knocked the thing over to get at them inside, which is very sad, but if it helps, be aware of moggies once they start cheeping. Good luck!