-16°F on 1-21-19.
No heat, tho floor is insulated.
Closed and heated waterer still worked.
Chickens were fine, gave me 9 eggs that day 11 the next,
except for the inevitable frostbite.
Before all the suggestions roll in:
I have copious ventilation, it's just always humid here, I have accepted that FB is gonna happen and I do not believe that coating combs is effective and can make it worse.
This last round of cold the lowest has been -12F or so....
...wind chill doesn't affect them while in the coop,
and I haven't let them out in days.