My coop has 4 vents, 2 on north and 2 on the south sides, the coop is pretty well protected from the wind on all sides except the west. The vents are each 7" x 9" and covered with metal screen. The wind direction in the winter is predominately from the west which is the end that the nesting box and plexiglass window are on. My question is, do I need to have covers on the vents for winter or just leave them open. Our winters here in Boise can get rather cold at times, like down into single digits but more commonly in the 20's.