Depending on location, cold weather creates more damage in the form of frost bite on the toes and feet. This causes the toe claw to be severly damaged or loss of. Frost bite will show in the form of white crust and obvious damage. This also applies to the comb. Any form of energy uses either in hot or cold conditions will effect the egg or meat production . I'v lived in central Ohio and witnessed frost bite in some cases so bad it crippled the bird. Temperatures in the upper 20,s are to be a concern. In houses of no electric,correct any and all draft air,insulation a must but be certain a barrier will prevent the bird from ingestion the material of insulation..inside a wall prefered. If possible the comfortable house will be only large enough for the bird to maintain it's own heat and still through daylite hours maintain ventilation. Don't put a chicken in a house with the capabilities of holding a hundred. Make sure the water is warmed and ckeck it often. Frozen water to a bird that needs water frequently cause energy loss and in most case death to the fowl. 6 inches of straw over crushed leave liter is excellent floor insulation but needs to be tended to when the ammonia oder gets strong..keep it dry. Night time is the threat of cold,prefare for it and deal with it. Hope this helps ,470fish
At night I shut off openings and provide a night candle in a steel lantern hung under the droppings board in my coop housing two pekin bantams.. Not much but better than nothing .. I think at -3c in UK. They are ok if dry and draught free. They do roost over the candle so may be it makes a small difference..... Mike UK.