Good morning Gotweim and welcome to the Michigan thread. Keeping your birds warm isn't as big an issue as keeping them draft free. They can handle zero temperatures with no issues as long as they are dry and able to get out of drafts. However, you don't want to have a coop that doesn't allow ventilation. Ammonia buildup can cause respiration problems. As long as there is ventilation above their heads you shouldn't have any problems.
Be sure to click on the link in my signature line. It will give you information about our upcoming Chickenstock. It's a great opportunity to meet some really nice folks, see some nice birds, and have a great time talking about chickens.
Be sure to click on the link in my signature line. It will give you information about our upcoming Chickenstock. It's a great opportunity to meet some really nice folks, see some nice birds, and have a great time talking about chickens.