I just created a profile with lots of pictures of our set up. Hopefully you can see it to use as a reference point for my questions. I've been reading conflicting information. We have a 10' x 12' shed in which we house our chickens; 8x10' of it is coop, the remaining 4x10' is storage. Before the frost hits, we'll have the interior insulated. We will be using a deep litter method for floor insulation. Do I need to get a solar powered lightbulb/ heatlamp or something like that to raise the temp of the coop during winter? I have 17 hens and 1 rooster, all dual purpose heavy breeds. Barred Plymouth Rocks, Black Australorps, Speckled Sussex, Silver-laced Wyandottes, and a couple of light-weight Easter eggers. They definitely don't fill up the 8' x 10' space, so I worry their body heat won't cut it to keep them warm. We live in upstate NY in zone 5 which has a low temp of -15 degrees or so; we've got windows on the East, South and West sides of the coop for passive solar heat. Also, (and please forgive the newbie question) if we deem it safe to let the hens out in the winter weather, we can leave the pop door open for their access, right? It will let in more cold air than *I'd* want to be in, but perhaps I'm underestimating the warmth feathers offer.