How much venting in cold climate passive solar coop

I'm hoping to get advice from people experienced with passive solar coops in cold climates.

Background:
I'm planning to build a passive solar coop with an attached run next spring. Have been enjoying information from the Back Yard Chickens website. Our area in western Wyoming had a recorded low temperature of -52 degrees F last winter. That is an extreme temperature for our area but lows in the -20 and -30 F ranges are not uncommon.
Coop will be an insulated 8' x 10' shed roof structure with clerestory windows facing south. Just under the clerestory windows will be the top of another, attached, shed roof structure (the run). The covered roof of the run will slope in the opposite direction. The run will be 8' x 25' with solid walls on the west and north sides. The south and east sides with have hardware cloth and be designed so that twin-walled polycarbonate panels can be attached during the winter months. There will be a wall between the coop and the run. The coop will have a 4" thermal mass material on the inside north wall and a concrete floor.
I want to keep 10 - 12 chickens with possible room for up to 20 chickens. Hopefully, the completed structure can be converted for use as a garden shed and green house. We live nearby the location of the planned building and I hope to use the structure for gardening purposes until we move there permanently at retirement.

The venting question:
Aside from venting in the wall between the coop and the run, what venting would be necessary during coldest times?
I plan to install four separate vents in the wall between the coop and the run. These four 3.5' w x 1.5' h vents with hardware cloth covered openings and hinged, insulated covers that swing open to the outside of the coop will provide 21 square feet of venting. Two of the vents will be arranged side-by-side as high as possible under the run roof and the other two vents will also be arranged side-by-side as low as possible in the same wall. I'm planning four separate vents for increased air flow control-two up high to let in warm air from the run and two down low to let in cool air from the run. This 21 square feet should be "adequate venting" for up to 20 chickens, right?
I'm thinking that these four vents with their insulated covers should be closed during the coldest times so I'm planning to also install another vent up high on the east wall which will be the down wind side most of the time. This vent will open to the outside-not under the covered run. What are size and design suggestions for this last vent?
Further information is that we're planning a drop down hood over the roost made of some material such as insulated tarp that will pull up to the ceiling during the days and warm periods. Clerestory windows will have framed rigid insulation covers that will also hinge up to ceiling during non-use. The last vent will be at the highest point in the coop-above the hooded area of the roost and hopefully let out any warm, moist air but not create any drafts to the chickens under the hood. Hoping to never add any heat in the coop.

Please offer any suggestions that you may have. Sorry to have rambled on so long. Hard to get descriptions brief

I don't have enough experience to respond to this I'm just bumping it up so hopefully you get an answer! It sounds like you really have things figured out though! User name @Blooie could probably help you out with this as I know she deals with very cold temperatures. Good luck!

WyoChickenFan said:

The venting question:
Aside from venting in the wall between the coop and the run, what venting would be necessary during coldest times?

Click to expand...

Too many variables to respond intelligently. I would go with what you got if you find you have ammonia smells and excess humidity you need more venting. This is how I solved my venting problems while housing 24 birds in a coop with a foot print of 4x8 feet.

I have a similar setup, with south facing windows the my shed's double doors which allow the sun to heat up the coop and cement floor (think heat battery) and keeps the coop significantly warmer. Our winters in CT aren't as cold as yours, but we get down to -20 and my insulated coop never dropped below 25 degrees. Most of the time the coop does not go below 35 even though it will be 0-20 at night and 20-30 during the day. I have two 30x50 windows on the east and west side of the coop which I use to control the ventilation and humidity. The top windows are open to some extent all the time, even in the dead of winter. If there is too little ventilation, the south facing windows frost over at night. I gauge how much to open the east and west windows by the south windows. Frost free is the goal. If I have frost, I have to open the windows more.

I also wrap my run in clear shower curtains, and this has a greenhouse effect, and keeps the water from freezing during the day. Plus I don't have to shovel snow out of the run!

Thanks for your bump. It worked!

Thank you, Hokum Coco, for your reply. Your input has given me some ideas.

Thomasboyle, your reply alerted me to use the frost as a gauge. I've seen frost on windows during the winter, but hadn't yet connected that it would be a good indicator of conditions in the coop. Seems that your setup is similar to what I'm planning. What do you use on top of the concrete floor? I'm thinking that I'll try sand first. Thanks for your input. I'm trying to gather as much info as possible before construction begins

I'm in Northern Wyoming, up near the Montana border. We don't get nearly the vicious cold that you get over there (I'm assuming around Pinedale, Big Piney, Evanston areas?) but we get our fair share, that's for sure!

If you could post some photos of your setup or proposed setup, that would help a lot. My coop has windows on all but the north side, and I keep them open except for the one in the direction the wind and snow is blowing that day. I also have vents on the top on all sides which are also operable, plus a gable vent on the east side which can't be closed. The pop door stays open year round 24/7. Their run is covered with plastic, and we were really pleased with that last year. Since the pop door is open, and because of the way the coop is vented, the slightly (and I stress slightly) warmer air accumulating in the run sort of flows into the coop.

I use Deep Litter in my coop and in my run. I like it because the girls burrow down into it on the bitter days. When one of them got up once, I put my hand in the hole she'd dug and it was toasty warm. I know a lot of people like sand, but I don't like it for this climate. It absorbs the moisture from the poop so that the chicken keeper can just scoop it up, but that moisture left in the sand freezes. Then what? Sure makes a hard place for them to land - the difference between coming down off the roost and landing in soft leaves and litter and hard, partially frozen sand was my final determining factor in choosing what to put on the floors. Besides, I've always wondered, what to you do with a bucket full of frozen poop, and how many buckets of it would you accumulate over a winter? I tried the poop board, and even though I didn't have that many chickens and was only cleaning the poop board, the amount of accumulated poop was staggering. Not again for me.

I use sand in my outdoor run, but I use hay inside the coop. I have ducks which nest on the floor, so sand would be too cold for them. Every week I had a new layer of hay, and after 6 months, I clean it all out. The bottom layers of hay completely decompose into a nice rich dirt, and I put that on our gardens in the spring.

Here are some drawings of my proposed coop. I have a friend helping me with the plans. We have made changes since the drawings were done, and are waiting for info to do some more minor changes before he sends me new plans, so I edited the revisions into the drawings.

I'm new to this wonderful site, so it took me awhile to get these images ready.

As I read the comments in the replies, I'm wondering if using sand for litter coop will work. My initial thought was the solar effect would warm the concrete floor and the sand litter to last through the nights during winter. I don't know enough about passive solar to know if that will actually be the case. I might wind up doing hay, which is readily accessible.

Thanks again for any thoughts you may have. I'm having fun planning this coop and want it to be right in the end.