How warm should a hen house be in the Wyoming winters when it gets down to -17 in the night and a high of 19 during the day? My husband argue about this and I put a heat lamp outside their door in the open coop. This provided some warmth during the night, but not too warm. Do Brahmas, opringtons and americanas require some warmth during these months where it gets really cold? Last night it was 27 and the hen house was 34 with the heat lamp.