What should we watch for when choosing material for the coop walls? We have access to some OSB (chip board)
I have OSB for my chicken coop walls. They have been holding up fine for 3 years now, but the outside wall was covered twice with barn paint. I'll probably have to give it a fresh painting this summer.
We have good insulation left over from another project, so we were thinking of insulating the floor and walls because of the cold winter temperatures of -30 to -40.
I live in northern Minnesota, and we typically get a week or so of -35F to -40F in the winter. Personally, unless you plan on heating the coop and have it climate controlled, you are probably wasting time and money by insulating your coop. With all the open ventilation that you should have in your coop, the inside coop temp should be about the same as outside. Insulating the walls and floor will not really get you anything when you essentially have large windows open for proper ventilation.
I use dry deep bedding in my coop, which acts as a natural insulator and gives the chickens something nice to walk on.
The most important thing, IMHO, is to provide a draft free place for the chickens to roost at night. Although you need good ventilation, you do not want any draft coming up from underneath the birds when they are roosting for the night. I have good cross ventilation just above the height of the roosting bar and more ventilation on the roof top. Chickens have a body heat of 105F, and they can fluff up their feathers to trap warm air against their body. A draft coming up from underneath the roosting chickens could defeat their ability to keep that warm body air trapped inside their feathers.
Of course, you should also get chicken breeds that are proven cold hardy for your area. Keep them healthy and they should do just fine. Good luck.