My 8 chickens reside in a small 100 year old smokehouse. The walls are about a foot thick of solid stone, and I have a small window for them to come in and out of. I have also added a small outdoor thermometer and the past few days it has been around -5F to -10F outside, but has been 6F to 14F degrees inside the coop. They are clearly a bit chilly, refuse to come out of the coop, and seem a little disgruntled, but honestly I don't blame them! This weekend we are headed out of town, but the temperatures drop to be about -20F outside. So far I have been vigilant with not having any heaters or bulbs other than a simple heated dog dish to keep them with fresh water because you just hear of all the horrendous stories. Because of the coming dip in temps my Dad has been asking if he should set up a little space heater on a timer to go off every now and then to keep them comfortable. I am also aware of moisture build-up and to be completely honest I really don't have a lot of ventilation (especially with them being closed in because we'll be gone). We have people coming over to feed them, but someone won't be able to monitor the heater in case anything goes wrong. I am ok with them being cold, I am not ok with having frostbitten chickens. Is -20F outside too cold? Help! I need your opinions!