Are they your only vents? You'll want some form of air circulation and ventilation, even when it's really cold.
Don't know how cold it gets in your neck of the woods. Here, I couldn't have a vent below the roost. It would be too cold on their booties while they sleep. And vents that are up high do a better job of removing that moist warm air from the coop.
That said, I only close my vents when it's going to be -15 and colder, but mine are up high above their heads. And the ridgecap/soffet vents are always open and operational.
Agree with the OP....can you lower the roost or add vents high up?? You want to have good ventilation, even when it gets cold but no drafts...... I have windows near the roost and will close those when it gets cold but I have vents up near the roof level in front and back of the shed that will stay open.... I did lower my roost a couple of feet though after the girls moved in and I saw it for real, not on paper.....
I think the answer is "no" to keeping windows open, but "yes" to keeping vents (once you create some more) open
From what I understand, your existing openings will be a problem in an Indiana winter because they are not at the top of the walls and because they are located where they will blow breezes at the hens' undercarriages as they roost.
I would suggest adding new vent openings, perhaps 6-12" tall and most of the length of the wall (other arrangements are possible of course, this is just a pretty good generic arrangement) on at least the south and/or east walls. Then you can leave *them* open, wholly or partly, pretty much all winter; close the windows; and have good ventilation plus comfy draft-free chickens.
Close the vents on the upwind side; leave the downwind side open. Yes, some breeze and maybe even a little snow will swirl into the coop in some weather; that is OK.
I feel like my chicks would be warmer at night with the vents closed.
I know, everybody does
, however what you will end up with is a reasonably-cold and VERY HUMID coop, which will give your chickens frostbite at temperatures they would have no problem with if the air were DRY i.e well ventilated.
Chickens put out vast quantitites of water vapor, and frostbite happens at far milder temperatures in humid damp air than in dry air. Honest. Close your coop up tight, get frostbite. Every winter we see a lot of posts about this, you can check the archives if you have lots of time to browse threads
The vents are at each end of coop and coop is 8 feet long by 4 feet wide. When it's raining or snowing I feel like leaving vents open can cause some rain or snow to blow in.
Ideally the vents would be located up under a roof overhang where they get shelter from most rain; and as mentioned above, if you have sufficient ventilation openings you can easily just close down the upwind side. If a little bit of snow blows in that is not a problem, not the way shutting the vents all up and creating a little humidity-and-frostbite chamber is a problem