About 10 inches per bird standard size, little more for a jersey giant. So you need about 260" of roost length, not everybody gets along, so add about a foot for that-272". Use a 4 inch flat roosting bar, to keep their bodies warm and to provide balance. Try not to stagger at different height as they will all want to be on the tallest. 18 inches from the wall, 12 inches between each one and if you do poop boards no higher than 10' from the bottom of the boards or they will sit under the roost board and get pooped on! Keeping a insulated, ventilated-but draft free coop will keep the girls toasty. In another words, keep the ventilation up high, higher than the roost, you want moisture exchange--a damp coop will cause frost bite. If you heat the coop, they will not get as thick of a under coat of feather--then if the power fails, your in for losing some birds. Search the thread on here from Alaska, and read how they keep them. I have one 40 watt light that's on a timer in my cop--Not for heat but to keep them at 14 hours of light for eggs, my vents were 4 feet above the roosts, because i live in the deep south my current coop is un-insulated. Yes, it's not as cold here--the same principles apply in colder weather. You can give them a coating on wattles,combs of Vaseline to prevent frost bite--I only did on night below 35*F. Remember our grandparents did this long before electric and their birds survived fine. If you have trouble with the birds this winter you may want to consider cold hardy breeds next year like,Ameraucana , Australorp, Brahma, Buckeye, Chantecler(extremely cold hardy), Cochin, Delaware, Dominique or Dominiker,Faverolles, Jersey Giant, Orpington, Plymouth Rock, Rhode island Reds are cold hardy except their combs.