After 25 years, I have chickens again.. I built a new coop and used an old p/u topper for the roof and wanted to show the air vents I made for the roof, as the topper is pretty air-tight. The picture didn't turn out so couldn't post it. I used 4" pvc pipe and an ice cream pail for the top. Drilled 1" holes all around the pipe and caulked it in place in the roof. The pail sits on top of the pipe and comes down past the holes to keep out the rain. Seems to be working well. Finias