Crunching numbers for adequate ventilation

[Sunshine Flock]

No tail between my legs here. For all the time I spend in the forums, there are lots of things I'm still needing to iron out, and one is chicken coop ventilation.

I converted an old shed to a chicken coop. The interior floor space is approximately 33' square, and I have five Welsummer hens and one rooster.

The goal was to replace the roof so the coop will have more than four inches of overhang and to increase the ventilation all around in the eaves. I'm on track for doing that in the spring, but a couple of things came up that made me realize this should happen now.

1) I covered the three windows with Lexan for strength and sunlight. The day after I installed them, I noticed a dusty swirl pattern on the inside of the Lexan. It took a few days for me to realize moisture was the culprit.

2) In another discussion, someone said we should have at least one square foot of ventilation per chicken. I knew this; I've seen this mentioned in the forums, but I never bothered to do any measurements.

Thankfully we're in a warmer climate, but the ventilation in my chicken coop is still inadequate. So today I measured the ventilation and came up with this:

- The ventilation in the eaves along the east side of the coop is 113.25" square. And on the north side I have 128.25" square of ventilation. It looks and sounds sufficient, until I converted it to square feet:

For six chickens in a 33' square chicken coop, I only have 1.67' square of ventilation.

The structure isn't air tight, but the swirling vapor pattern on the windows tells me they need more ventilation. I knew I should have measured, but I got distracted by other projects. It's really kind of surprising it only adds up to just over a foot and a half of ventilation.

So, am I understanding all of this correctly? Too little ventilation based on those numbers, definitely follow the square foot per chicken rule? It's amazing to me that people in cold climates will actually open doors and windows to increase winter ventilation. But it's starting to sink in now and make sense.

 

[ChickenCanoe]

Basically, you need to remove the lexan on at least 2 of the windows if not all three and replace it with hardware cloth.
The main reason we have coops is to keep them safe from nocturnal predators and secondly to keep rain off of them. Not to 'coop' them up in an indoor environment or for warmth. They need fresh air.

 

[Sunshine Flock]

Basically, you need to remove the lexan on at least 2 of the windows if not all three and replace it with hardware cloth.
The main reason we have coops is to keep them safe from nocturnal predators and secondly to keep rain off of them. Not to 'coop' them up in an indoor environment or for warmth. They need fresh air.

The Lexan is a framed storm window.

I have hardware cloth on the exterior under the cedar window frame, and recently I added another layer inside as well so I'll feel better about having them open during our long hot summers.

Why you feel the need to tell me the purpose of a chicken coop, I don't know.

Let's just forget about this stupid discussion I started, if this is how I'm going to be treated.

 

[ChickenCanoe]

It isn't a stupid discussion if you don't have sufficient ventilation.
You've already calculated that you need much more which is why I recommended you reopen the windows.

 

[Better Than Rubies]

Let's just forget about this stupid discussion I started, if this is how I'm going to be treated.

CarolinaSunshineFlock, it's okay; I don't think ChickenCanoe was saying that to be rude. I can't help you with your questions, unfortunately, as I'm not knowledgeable in that respect, but I do hope someone comes over here and gives you the help you need. There's nothing wrong with asking questions; that's mostly what BYC is here for. I'll tag @TwoCrows; she's the main one I can remember who I'm pretty sure is really knowledgeable about chickens and their care.
Sincerely,
Cara

 

[Egghead_Jr]

Is the shed a single slant roof? and at what pitch or degree does it slant?

If it's a gabled roof then you need venting in top of gable each end to exit air intake from eaves.

OK, reread your post and see you have venting East side and North side. If your venting along the pitch it's not working with convection. You need the vents on low end of roof and high end to create a suction and blowing effect. That will greatly increase your rate of air flow. I dare say I've less surface area of venting than you do with 15 birds in the coop. Perfectly dry in there.

Can you better explain the roof line and where your vents are located?

 

[TwoCrows]

Is the shed a single slant roof? and at what pitch or degree does it slant?

If it's a gabled roof then you need venting in top of gable each end to exit air intake from eaves.

OK, reread your post and see you have venting East side and North side. If your venting along the pitch it's not working with convection. You need the vents on low end of roof and high end to create a suction and blowing effect. That will greatly increase your rate of air flow. I dare say I've less surface area of venting than you do with 15 birds in the coop. Perfectly dry in there.

Can you better explain the roof line and where your vents are located?

This is what makes good ventilation...a pitched roof, vents in the eaves on the low side and vents in the eaves on the high side. What happens is, the pitch itself creates a natural draft so that the air will come in the low side of the roof and travel up and out the high side. If you keep your birds roosting lower to the floor, this gentle air movement along the ceiling will not disturb the warm bubble of air the birds have created through body heat, however it will pick up all moisture from breathing and pooping and whisk it right out the roof. Aprox 1 square foot per bird of venting and you will never have trouble with ventilation or frost bite again.

Now, on windy nights, you can block off a few of the LOW side only to keep the air from moving too fast, but never close them all off no matter how cold it gets.

This is the system I use in my coop and myself and birds love it!!!

 

[Egghead_Jr]

One square foot per bird is sufficient for passive venting, like a large window. I have 15 birds in a small coop. There is not even 2 square feet total ventilation yet it's sufficient and dry due to being pure convection venting. Sucked in low end and pushed out high end. Even more efficient if low end is aided by the prevailing wind direction.

Let me just give an example of how one of my current coops is vented. I didn't sheath the roof, the entire top was secured with hardware cloth to keep weasels out. High hat metal roofing was screwed direct to the four roof supports. This makes for the only venting, the area of each high hat of the roofing for the seven foot length of coop. Air sucks in via natural vacuum along low end and is pushed out the high end. Again, 15 birds are in this coop and it's dry. The air flow needed is 0.5 cubic feet per bird per minute. My less than 2 square feet of total venting meets or exceeds this USDA stated minimum air flow requirement.

 

[aart]

Some pics would help.
Don't get stuck on numbers...they are just guideline.

 

[BantyChooks]

The Lexan is a framed storm window.

I have hardware cloth on the exterior under the cedar window frame, and recently I added another layer inside as well so I'll feel better about having them open during our long hot summers.

Why you feel the need to tell me the purpose of a chicken coop, I don't know.

Let's just forget about this stupid discussion I started, if this is how I'm going to be treated.

Nobody is attacking you. Gotta remember that when people reply to threads, they also (at least I do) talk for the benefit of other newbies reading. Maybe they haven't come across ventilation information before and so would find CC's statement that they need way more ventilation than many would expect helpful.

You've received some great information already so I won't repeat it.