The roof vents on my 81 Excella II are deteriorated and leak. I was thinking of just covering them with aluminum to replace the cracked plastic. The amount of light that comes through them is minimal so I figure Aluminum would be a lower maintenance option. It looks like there is a top surface piece of plastic and another one below that. Is this done to add some insulation? I may also insulate them. The way these things are designed not much air can get out. There is the big light diffuser on the bottom and then a metal boot that comes down below that. Unless there is a fan in there I can't see the vent being open or not is going to make much difference. I am not going to destroy that function just put metal where the plastic is that is pretty much gone already.