When we were building the coop we were given the suggestion by a local friend with chickens to add some insulation to our coop. So when we built it we put foam board insulation in the walls. The ceiling and the floor are not insulated. We didn't mind cause it was free. I had planned on closing up the windows, but on your suggestions I will keep them open. As for the duck hut, again I had left over insulation that I just put under the tin, the rest is very open and is more of a shelter then an actual coop I can always take the insulation out of the hut if I wanted to. The coop is another story. I'll see how the coop does and can always add more vents if needed, but it is pretty airy when the big windows are open. I'm just so proud of our coop It only cost us just under $50 to build the whole thing. We just bought a few 2x4's and the hard ware, the rest was recycled from our barn or was given to us from our parents.