Ventilation formula - is there one?


10 Years
Jan 5, 2010
Skiatook, OK
how do i figure out, and dh needs to know by tomorrow, exactly how much square feet of ventilation he needs to build? We have the walls up and framed for the doors and two windows.

Here is how our coop is designed.

it is 8x12 with a long window on the two 8ft sides, the bottom of the window starting at 16 inches above the floor. This will make a great breeze in the summer.

He is planning on putting a ridge cap vent on, so that will be 12 ft in length.

He is also planning on putting some sort of louvered vent on each gable end. He was trying to find some continuous soffet vents but i am not sure he has found some that will fit in our budget.

DO we need the soffet vent or will the ridge cap and louvered vents on the gable ends be enough in the winter?

He would really like a formula, fi anyone has one.



9 Years
Mar 1, 2010
Plainfield, CT
I'm a newb here and still haven't built my frist coop....but from what I've seen in the coops section, it seems putting some windows up high is also a very good way to go. I've been on here religiously the past three weeks, and haven't seen a formula...just that ventilation is very important....and most have lower windows and higher windows...just an observation...good some pics as you guys go!


Love My Chickens
10 Years
Jul 28, 2009
Floyds Knobs, Indiana
My Coop
My Coop
link is a good general guideline. I will say that my winter ventilation was far less than the general guideline, but I have very few birds based on my space, and I'm a clean-a-holic in my coop. So my humidity always stayed low in my coop (less than 50%), and I never had amonia issues. Like you, I have windows in addition to my reg. vents. So my spring, summer, fall ventilation is plenty...just not my winter, since my windows were kept shut all winter.


Flock Mistress
12 Years
Apr 20, 2007
Ontario, Canada
There is no generally-applicable formula to give you an exact accurate answer because it depends so much on the peculiarities of your coop, site, number of birds, climate, sanitation habits, etc etc.

My suggestion is that it is way way better to build as much ventilation as you might need in a 'worst case scenario' and then have it turn out you don't have to have all of it open most of the time (though in summer there is NO SUCH THING as too much ventilation!), than it is to underbuild and have to be out there in January with the reciprocating saw.

A safe rule of thumb would be 1 sq ft per chicken or if you can't bring yourself to do that then at least 1 sq ft per 10 sq ft of coop floor space; but in some coops you will not technically end up requiring this much, and in others (very crowded or damp ones, or anything in a hot-summer area) you may need more. It is worth making sure that you have both sufficient winter-type ventilation AND sufficient summer-type ventilation, as the needs are rather different.

Good luck, have fun,


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