I have a question about heating my coop in the winter. I live in upstate NY where it gets pretty cold during the winter, but normal temps are 0 - 20 degrees. I have read a lot about how chickens put off a ton of heat and moisture and that their body heat is sometimes sufficient to heat the coop for them to be comfortable. So I guess my question is will 4 hens be enough to heat a 4' wide x 6' long x 3 1/2 ' high coop? I want to get 1 or 2 more hens, but I don't want to over crowd them. I would rather not run electric if I don't have to.