Hi, I am new to raising chickens, this is my first winter, and I have a few quick questions. I have seven lovely, laying girls who are all very cold weather hearty. We have a permanent 10x10 insulated chicken house with a covered, fenced in chicken yard attached. I live here in the northwest and recently the temperatures have been dipping down into the upper 30's at night. In reading some of the forums, I have been adding more hay to the chicken house floor to keep them warm, in lieu of a heater. In the chicken house there is a connecting chicken door which has a hatch that opens and closes to let the chickens in and out. To date I have been keeping the door open all the time, but now it is getting colder and I am worried I am letting too much warm air out. So my question is, should I keep that hatch door closed at night and then open it every morning so as to keep it warmer inside during the night? When or should I ever, consider putting in a heater light for the girls? It gets very snowy and cold here and while their house is very well built and insulated, I just worry that they may be cold as the winter progresses. Any thoughts?