There are all sorts if thoughts on insulation. It can be a mouse nest haven. I have insulation on my roof. And that is to help with condensation and dropping on my birds. Two winters ago I insulated the west and north walls only with removable foam boards and press board inserts place able between the stud walls and this helped moderate the extremely cold nights. As well as moderate extremely hot days-- my coop will be cooler on hot days. Last year after reading a popular chicken blog I found a reflective material that's suppose to use sun from the windows and reflect back warmth. It's called Reflectix. It's a silvery bubble wrap. We had a mild winter by Minnesota standards last winter as you know but I was happy with it. The mice can't get into it. It's washable. It did not really warm up the coop a whole lot. Poop stayed froze ( I wanted that) . Cluckies has reported her birds were a bit skiddish of the silver walls. When I put mine up I did 1/2 one week and 2 weeks later the rest. My birds didn't seem affected by it. I will give my Reflectix another year to give full endorsement but some of the big coop makers are using similar reflective material in their coops now to refract the light and heat.
