Here it is not even winter yet & I've read three threads about people getting there heat lamps out. I know I live in Texas & its the heat I worry about but last winter my coop was 19 for many days & my birds did fine. Adding heat could actually make your birds sick. There kinda like us you get warm go outside & its cold you could possibly get sick. Heat lamps can cause fires so the best advice is to keep the wind off your flock. The birds will snuggle if they get cold & believe me they can keep each other warm after all they don't wear down jackets for nothing.