I am in northwest Ohio and have had several days in the 20's. birds seem to be doing fine with no artificial heat. I have researched both sides of the argument and I don't plan on using any artificial heat and was wondering how you other Buckeyes did last year with your birds when it was -20 and-30. I have plenty of ventilation about 6 inches above the roosts.
We don't use any heat sources for our adult birds either, and none had any frostbite last year even with temps inside the coops at -10 to -20F. (We worried about them a lot but they surprised us with how well they did).
My coops have 2x4's set wide side up as roosts so toes are not exposed. My floors are all raised off the ground and we use pine shavings cleaned often. In winter, I switch out the regular waterers to heated dog bowls full of water inside the coop. I don't fret over humidity because unless there is forced air or artificial heat inside a coop, the inside humidity is very close to the outside humidity. It didn't matter whether I had a big open bowl of water inside or outside. It typically was the same, so I decided to just keep it inside because they drink more often that way.
As long as there is space above your roosts for warmer air to rise, along with ventilation up high, you should be able to keep moist air from settling back on the birds. Mine tucked their heads under the wings on the coldest nights too.
All that said, this past summer we built 2 more coops and my husband fully insulated them with R-13 insulation (and insulated the original one too) because we felt that it would help keep them be more comfortable.
For the babies out there currently, I use a home made cookie tin water heater and set their chick waterer on it. For warmth, they have a brooder heat plate (Premier brand) so no risk of fire
All the coops have chicken doors open to the outside runs all day long unless there is freezing rain, then they stay closed. We also put up tarps up on the side of each run that gets the most wind.