Ventilating for extreme cold

[AK Michelle]

I live in Alaska, much of my winter is around between 20F and -10F (or so) with occasional dips to -35F.

I have just completed construction on our barn that will be the new chicken coop and need to decide how much ventilation to add. We have a very dry climate, our outdoor winter humidity is 30% - 50% based on my incubator's hygrometers left on the shelf over the winter.

The new coop is 20' X 40', insulated cement slab, with foam insulation in the walls and ceiling and a single pitch room (so the snow slides off away from all the doors.)

The ceiling is built using 12" joists

The builder used plywood to sheet the interior ceiling, then blew 3" of foam insulation onto that and then put the roof sheeting on, leaving approximately 9" of air gap between the insulation and the roof.


The eves were enclosed with screened vents on both the high and low sides...

Our plan is to cut through the ceiling and the foam but not the outer "roof" layer. Our thinking is that the outside lower vents will let cool air into the channel, the outside upper vents will be where the warm air will escape. We were planning on putting the interior ceiling vents both on the low and high sections of the joist channels. The vents in the lower portion of the ceiling will let the fresh air into the coop while the higher ceiling vents will let the warm moist air escape. At least that is our hope...


So now, my question is... how many inches of ventilation will I need? I am thinking of using the vent covers that I have seen inside of homes for air returns that are sometimes like 6 or 8" by 18 or 24" (I'm just guessing - we are going to the hardware store to look at options)

Ok guys and gals... Your opinion matters. I can't wait to hear from you.

 

[AK Michelle]

H2B isn't sure we can use ceilings vents for air intake. He thinks the gaps around the doors and pop doors will be the air intake. I don't think that will be enough intake... but I could be wrong.

It hadn't occurred to him until he read the previous post that I was hoping to get some intake from the ceiling vents, but now thinks it might work but we may need to use some channels for low ceiling (intake) vents and other channels for the high (exhaust) vents.

 

[Fred's Hens]

First, let me congratulate you on a spectacular barn coop. Outstanding.

Our temps are virtually identical to yours in the winter, here in northern Michigan. My barn is quite similar to your barn, except I do not insulate. My ventilation enters on the low roof eve and exits on the high roof eve, just as you have designed. It works very well. You could consider a 12x12 vent, placed high up on the high wall. This might be standby exit vent, if you find you need to vent more fumes or ammoniated gasses. You can always have a cover designed, to close it off, should you find you do not need it. It might also prove to be helpful during those odd hot summer days. In other words, anything you install as a back up vent, on the high wall or on the roof, would be great, just in case. Gotta do it now, because doing it in the dead of winter isn't possible, of course.

Our winters are extremely dry, so we are fortunate. Is your area of Alaska a damp, wet cold? If it is dry with relative humidity below 30% most of the time, the humidity will be created almost entirely by your birds breathing and pooping.

Again, awesome barn/coop!!!

 

[AK Michelle]

Thanks Fred, yes we are very dry here as well.

Our barn/coop is 800 sq feet, how many sq ft of venting do you think we need?

Do you think we need to put the intake and exhaust in separate channels.

We are hoping to install the vents and pop doors in the next couple days so we can finish the interior pens and get the birds moved in.

 

[ChickenCanoe]

Nice buildings.
First off we're not as cold as you guys.
But we're very humid and that is a problem in winter.
We can get to - 10. Still, ventilation is way more important than warmth.
We also get over 100 in the summer. Birds here die in the summer but not in the winter.
My new buildings have 1' sq. ventilated area for each 4 - 5'sq. of floor space.
They can handle lots of things except bad air.

If I were you, given the nice ventilation you already have, I would cut big windows in the east or south side and put a solid shutter hinged that you can close on the coldest nights and if you have electricity, aim ceramic infrared fixtures at the roosts for the coldest nights.

IMO the idea is to prevent frostbite. Given a warm place at night and turning them out to colder temps in the morning is worse than no heat at all.

 

[Fred's Hens]

Ideally, the air is channeled in and out along the same space between the rafters. They sell waffle baffle vent guards at Home Depot and building centers everywhere. I like them very much. They are cheap, they work. I'd consider using them. I'll see if I can post a link. I suspect you already have these mind?

Our barn does "intake" some air through the door cracks. It is a barn and not sealed as tight as a house, although, the walls are sealed well and the 20x24 barn is vinyl sided to be maintenance free. But 90% of our air intake is through the lower eve. The lower eve is 7' high. The upper eve, where the air exits, is 12' high.

We have had some hot summer days, so all the intake spaces and exit spaces are wide open. This fall, I will dial it down to 4 or 5 intakes and leave the exits wide open. My spaces are 24" wide and 4" tall, or about 1 sq ft each. There are 12 of them on the lower eve and 12 of them on the upper eve. Thus, 12 sg ft of intake and 12 sq ft of exhaust. But this is, again, the summer configuration. I'll dial that back to 4 or 5 sq ft of intake, but leave the 12 sg ft of exhaust year around. This is air pressure science, thus the air will not exhaust any faster than the "make up air" from intake enters.

I am also computing my air intake, via the cracks around the 4 doors to be an additional 1 sq ft of air intake. Hope that helps.

 

[PurpleChicken]

Since it's already done I'd wait and see how it works out as is. The number of birds you have and the frequency of pine changes will have a big impact.

Dini just asked me to put her on a plane to your house.

 

[AK Michelle]

Quote:
She's not old enough to fly unaccompanied, you'll have to escort her. I'll prepare the guest quarters.

 

[AK Michelle]

Quote:
Luckily we don't have any humidity and almost no heat to speak of. Our cold is very dry so I want to make sure there is enough fresh air getting into the coop to allow for adequate flow of foul air to get out. If there is no incoming air into the coop then the warmer air cannot eescape as that would cause a negative airflow.

We don't heat the coop above zero or the birds will get shocked going in and out. Not to mention the condensation and other issues. when it is colder than -20 I want to be able to leave the pop doors closed but that reduces the fresh air intake to roughly 8 sq inches, not enough for 800 sq ft of chicken coop.

It's a puzzle to be sure...

Glad you have a system that works for your climate.

 

[AK Michelle]

Fred's Hens :

Ideally, the air is channeled in and out along the same space between the rafters. They sell waffle baffle vent guards at Home Depot and building centers everywhere. I like them very much. They are cheap, they work. I'd consider using them. I'll see if I can post a link. I suspect you already have these mind?

Our barn does "intake" some air through the door cracks. It is a barn and not sealed as tight as a house, although, the walls are sealed well and the 20x24 barn is vinyl sided to be maintenance free. But 90% of our air intake is through the lower eve. The lower eve is 7' high. The upper eve, where the air exits, is 12' high.

We have had some hot summer days, so all the intake spaces and exit spaces are wide open. This fall, I will dial it down to 4 or 5 intakes and leave the exits wide open. My spaces are 24" wide and 4" tall, or about 1 sq ft each. There are 12 of them on the lower eve and 12 of them on the upper eve. Thus, 12 sg ft of intake and 12 sq ft of exhaust. But this is, again, the summer configuration. I'll dial that back to 4 or 5 sq ft of intake, but leave the 12 sg ft of exhaust year around. This is air pressure science, thus the air will not exhaust any faster than the "make up air" from intake enters.

I am also computing my air intake, via the cracks around the 4 doors to be an additional 1 sq ft of air intake. Hope that helps.

Now I'm confused. Are you saying to use the waffle baffles (yes, I know what you mean) between the inside of the coop and the air channels in the roof? I thought they were just for the eave vents.

When it's not freezing I plan to leave all 4 of the 4 foot windows open plus all 3 pop doors will be open during the day so it should be planty of air for them

Predators won't be an issue because we are getting livestock guardian dogs. Our birds free range a 3 acre pasture and it's the only way to let them do so. The dogs won't let anything get to them, day or night, so the coop will only be closed when we are having our freakishly high winds.​