We are building a new/bigger coop. I have some questions about ventilation and roost placement. I'll give as much info as I can to help with any suggestions on the matters. I will also include two photos.

Ok, so I am putting vents on each 8' end as drawn. I have it that way now in my old coop and works out well (much smaller coop). They will always be open (unless suggested that I create shutters for them, although it would be very hard for me to reach them without ladder I think).
There are two windows that will also be able to be left open on north side if needed. (more in summer than winter though)
Our plans are to put in a long vent with shutter on the back 12' wall that is up against fence. Being 12' we might put in two "semi" long vents instead of one super long vent though.
I wanted to put the roosts on that same back wall though. Will that be a problem? Too cold, too drafty?
Most of the time the winds are either coming from the East or the West. The South side (where I want to put long vent and roosts) is pretty protected by the fence.
I'm in Vermont and winters can get brutally cold, many times being in the negative temps and even lower with windchill. Also the humidity level is usually pretty high through the winters too. I do not heat my coop. This may seem a silly question but will there be higher chance of frostbite with a bigger coop or less? If I absolutely have to I can put a heat lamp out there on the really brutal nights but I really do not want to. I am too worried about fires so would prefer not to.
Now the roost questions. I have four big hens now (Buff Orpingtons). I also have six chicks that will be joining the big girls when they are ready. How many roosts should I make available? Right now I have one long roost and the four girls all cram together leaving most of it empty. Can I just have a really long roost for ten hens or should I have at least two, or more? I would think though that its good for them to all be together, especially in the winter, to help keep them warm? However many roosts I have to do they will all be single roosts (with poop boards), I don't like the "'ladder" roosts, if that helps with answers.
For what its worth the breeds I have are Buff Orp x 4, Speckled Sussex x 2, Barred Rock x 2, Easter Egger x 2, providing none of the new chicks are boys.
The picture below is coop in progress. The long vent/vents I want to put under the eaves like seen in the picture, but on the back side of the coop. We are hoping to get more work done on it Friday and Saturday. I hope I didn't ramble too much. I'm famous for that, lol. Thank you in advance for any help/suggestions.

Ok, so I am putting vents on each 8' end as drawn. I have it that way now in my old coop and works out well (much smaller coop). They will always be open (unless suggested that I create shutters for them, although it would be very hard for me to reach them without ladder I think).
There are two windows that will also be able to be left open on north side if needed. (more in summer than winter though)
Our plans are to put in a long vent with shutter on the back 12' wall that is up against fence. Being 12' we might put in two "semi" long vents instead of one super long vent though.
I wanted to put the roosts on that same back wall though. Will that be a problem? Too cold, too drafty?
Most of the time the winds are either coming from the East or the West. The South side (where I want to put long vent and roosts) is pretty protected by the fence.
I'm in Vermont and winters can get brutally cold, many times being in the negative temps and even lower with windchill. Also the humidity level is usually pretty high through the winters too. I do not heat my coop. This may seem a silly question but will there be higher chance of frostbite with a bigger coop or less? If I absolutely have to I can put a heat lamp out there on the really brutal nights but I really do not want to. I am too worried about fires so would prefer not to.
Now the roost questions. I have four big hens now (Buff Orpingtons). I also have six chicks that will be joining the big girls when they are ready. How many roosts should I make available? Right now I have one long roost and the four girls all cram together leaving most of it empty. Can I just have a really long roost for ten hens or should I have at least two, or more? I would think though that its good for them to all be together, especially in the winter, to help keep them warm? However many roosts I have to do they will all be single roosts (with poop boards), I don't like the "'ladder" roosts, if that helps with answers.
For what its worth the breeds I have are Buff Orp x 4, Speckled Sussex x 2, Barred Rock x 2, Easter Egger x 2, providing none of the new chicks are boys.
The picture below is coop in progress. The long vent/vents I want to put under the eaves like seen in the picture, but on the back side of the coop. We are hoping to get more work done on it Friday and Saturday. I hope I didn't ramble too much. I'm famous for that, lol. Thank you in advance for any help/suggestions.