It got to -27 last night here in NH! Chickens all seem to be doing well in spite of the cold weather! Coop is insulated and I have a 150 watt heat lamp on a timer 40 min on 40 min off. I hadit on a themostat that had it on below freezing but found they didnt need it that much even colder than that so I put it on a timer so it is off more and not using as much elect. I did have most of my eggs frozen though! Had to work all day so they were in nesting boxes all day!