I have a grow out coop that needs windows right now and we have been toying with different ideas. Today I saw something that might work in Wallyworld. Back by the fans and air conditioner filters they sell metal vent covers that are slotted. Coundlnt you use a couple of them. they would give ventiataion and you wouldn't have to worry about predators coming in. Seems to me if you cut a rectangle hole the same size you could just slide it in or silicon it in. idk I am not a builder but its a thought.