Been down to -25 here and I have similar breeds (but add some non cold hardies like leghorns in my case).. All were fine, no frostbite yet.I have 24 of various breeds (all suppossed to be good cold weather breeds) and they are in a coop (converted barn) that is 12ft by 24 ft..so heat from each other isnt a factor that will help. I am worried as we are suppossed to get to a HIGH of -10 on onday meaning probably -20 at night. I am trying to decide if I should add a little heat or not. So far, its been down to about -5 at night and no signs of frostbite (I put vaseline or olive oil on the roos comb).
Breeds: Cochins, Opringtons, Faverolle, Barred Rock, Wyandottes, Sussex, Brahma, and Black sex link, Then some mixes as well