I need to seal my crawl space vents

[SteveCity]

They make vent covers for crawl spaces but mine are an odd size. I need a recommendation for some sort of black, weatherproof plastic (or something) that can be cut to size and caulked into place to keep cold air and summer humidity out.

I’m not able to block from the inside so I’m trying to make this look as good as possible and cutting to size and tucking up against the metal vent will work best.

 

[Snoonyb]

You are aware that when you confine a normal vented area, like an underfloor area, you'll not ventilate the ground moisture and mold will develop affecting the framing as well as the insulation.

 

[SteveCity]

You are aware that when you confine a normal vented area, like an underfloor area, you'll not ventilate the ground moisture and mold will develop affecting the framing as well as the insulation.

From my research it’s better to close off vents to reduce humidity. I’m not concerned about humidity as we go into fall/winter but when it’s humid again and it goes above 60% in the crawl then you have a greater chance of mold.

However, I’m still learning and I’m open to all opinions.

Currently I want to close the vents to reduce the cold air that’s coming in.

 

[Snoonyb]

There are any # of products available, plywood, foam board, plexiglass, acrylic, none of which I would use, because the floor will still be cold, because the earth is cold.

You'll still be conducting heat to the now enclosed space, and hot air has the ability to hold more moisture than cold air.