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 😀