Their coop is insulted roof and all.. the floor is layered deep in shavings.. and I have so many big fat fluffy butts in there... It is noticeable warmer when you open the door. I leave a window cracked open for extra ventilation... there is ICE on the outside wall around that window from the amount of heat and humidity escaping . I don't need a heat lamp in there nope.. they are doing real good.