gemsworld wrote:
I checked the rubber seal around the metal flange and it's in good shape.
The entire vent assembly is in good shape. I think the vent cover doesn't sit snug enough against the thin rubber seal and lets air get through.
I'm going to see if the hardware store sells thin, self-adhesive weather stripping that I can stick to the vent cover flange to lessen the gap between the side of the rubber seal and the vent cover.
I restored my roof vents and used a butyl rubber sealing strip I purchased at Ace hardware. It was similar to the sealing strip linked to above but bigger and more durable. The plastic vent cover should contact this sealing strip when closed. IIRC, I used some adhesive to hold the strip in place.