i have been putting a 2x4 mat under my tent liner and keeps the tent temperatures from dipping too low i put them on controllers so they don't have to be on all the time and doesn't get too warm. actually set all my tents this way, but the seedling tent stays on all the time. it's nice because it offers another level of temperature control, and when it's from the bottom the plants seem to like it better than a room heater.