There is no reason any of your birds would die in that temperature. You can't freak about wind chill as your birds are in a building so that has no bearing. My birds go into their run in this cold. We use a tarp to cover 7 ft of one side and 5 ft other on 10x10 run. Being on a river that north corner is prevailing wind. Mine do fine, bite of frost bite on the roosters comb tips but nothing serious. Our morning low was -15F, high today of -2F and low next morn will be -12. Our coop is uninsulated and our birds stay in run all day in this weather.
