I have a chicken coop that is about 6x4. It is getting cold so I placed a heat lamp in the coop. I went in there about 30 min later and the coop was like an oven. I'm planning on putting a smaller light in but I was just wondering...does a chicken produce better because it is warm or because of the light? How warm do chickens like their coop to be? Should I even heat my coop...my 7 chickens are full grown.