confussed?

[salt and pepper]

2-3 square feet can work. Buuuuuut, still ensure you have plenty of ventilation. Because it does go to freezing there, and you could end up with a frosty coop. Another problem in small, poorly ventilated coops, is that the air quality itself is lousy. Not only with CO2, but ammonia from their waste. That opens your birds up to various respiratory problems. You really need good fresh air exchange.
Jack

So If a small coop is well ventilated, it's not such a problem? One has a 5 inch gap running around the whole roof line, the other's door is really large, and is never closed, but the largest one needs some work, I had a lot of frost bitten combs last year, and couldn't figure out the cause, and never thought it was form poor ventilation!!

 

[JackE]

So If a small coop is well ventilated, it's not such a problem? One has a 5 inch gap running around the whole roof line, the other's door is really large, and is never closed, but the largest one needs some work, I had a lot of frost bitten combs last year, and couldn't figure out the cause, and never thought it was form poor ventilation!!

If you have a bunch of birds in a small coop, you might need to have a whole wall open to get proper ventilation. I a lot further north of you, I have some birds with big combs, and I have never even had a hint of frostbite. My coop has a whole wall open year round. It gets plenty of air exchange. See the pic below.
Jack

 

[salt and pepper]

If you have a bunch of birds in a small coop, you might need to have a whole wall open to get proper ventilation. I a lot further north of you, I have some birds with big combs, and I have never even had a hint of frostbite. My coop has a whole wall open year round. It gets plenty of air exchange. See the pic below.
Jack

Thank you, I plan on making a large opening for ventilation this year.