It has been getting into the low 20's and per my van thermostat, as low as 17. I have a wooden coop but it is not insulated and i am doing the deep litter method. I have a 12 foot ridge line vent along with two windows on the east and west side of the coop and the pop door at the bottom on the north side. for the summer time, i leave the windows wide open and because my run is now predator proof, i leave the pop door open also. when the weather started getting colder, i have closed the windows down to where they are only open about 4=6 inches. Here are some pics taken earlier this summer and let me know if you think because of the window placement, them being open the 4 inches or so would be causing them to have a draft. Their roosts are above the window opening height, along with a poop board below the roost on the north side above the pop door. these windows are now open only 4-6 inches: you can barely see the pop door underneath: This is the window you see in the first picture, on the west side, you can see i have partioned off a bit of space for storage, so there is a lot more space between their roost and this window: The reason i am keeping the windows open, is i am worried about having enough ventilation. I really would like to continue to keep the pop door open all winter if i could, unless it comes down to extreme wind/snow storm. but i wouldn't mind closing the windows if everyone thinks i should.