I am sure vents are important, but because I have three fans in each GH and during warm weather can leave the doors wide open, I don't really see much value in my vents being open or closed. That being said, my orchid GH has a total of six vents at the base of the three sides (its a lean-to) and another near the roof on the side away from the door. and they are all louvered, so the solar blanket makes no difference. Air can escape between the polycarbonate and solar blanket material quite easily.
