Best window size for a fan

[CindyinSD]

Since it's for your garage, I revise my statement. Don't use cheap windows for your home--they will let flies in where they slide across one another. Get windows that coordinate with those in the house and are of similar quality, even if it's a detached garage. I really like @aart 's solution. You can do that and still not damage your window or deface your walls. You could also ask your carpenter's advice about additional ventilation options. Good ventilation in the garage is helpful whether there are chickens in there forever or not.

 

[ChickenCanoe]

Here's how I did my window fan:
https://www.backyardchickens.com/articles/window-fan-mount.75608/

Very nice! That's the same fan I have sitting on a window sill extension in my first coop on this property that was window compromised.
It blows into the building year round.

 

[hayley3]

Here's how I did my window fan:
https://www.backyardchickens.com/articles/window-fan-mount.75608/

That's clever!