How do I close and seal an old external vent?

Question

I was removing some ancient hanging cabinets in my small laundry room when I found an old vent of some kind. It had been completely hidden behind the old cabinetry. My dryer vents out through the roof so I want to close and seal this opening, especially before it gets really cold.

I believe the gist of it is that I fill the hole with insulation and put some drywall on the inside. I then cover the outside with some sort of aluminum plate or plywood. Any experts out there have input as to choice of insulation or external covering? I think the box is too big for the kind of spray foam one would use around pipe holes. I have stucco on the outside of my wood house. Also, should I remove the inner walls of the box or just leave well enough alone?

Answer 1

I would probably use some rigid foam insulation (2 or 3" is probably good, it's generally rated at R7 per inch - and you can stack it, it doesn't have to be a solid piece), and then use spray foam to seal it up around the edges and hold it in place.

It looks like a metal sill all the way around, so that's going to cause a lot of heat transfer anyways - ideally, to make it as warm as possible, get rid of the metal. You can also then pull off the trim and just put some backing in, and a piece of drywall (or plaster) to finish up the inside.

The most important part is making sure it's sealed to the elements from the outside, like rain/snow. You don't want water coming in and getting into your walls. Depending on the outside condition, get rid of the louvres. Ideally you would put a piece of plywood in place and then if you have siding on the rest of your house, put siding over that as well. You might also be able to just leave the lovres there, but seal them up (with caulking outside, spray foam inside) so they don't open and don't let anything in.

Answer 2

I am very concerned about moisture and vermin in this case. You need to seal the outside properly, much more than the inside cosmetics...it actually is a fairly easy fix. Just don't want your place to look like a trailer repair! There are always a lot of considerations that are hard to get from a short description. You really need to seal the outside hole and get rid of the vent hardware first, waterproof it, insulate it, then fix the interior.

Answer 3

Any sort of insulation would do - it might be whatever you can scrounge. It doesn't seem worth buying a whole roll/sheet for such a small space.

I might be tempted to fix a plate on the inside to stop any water getting in. This could be any suitable material and it might be easier to fix from the inside.

As for the interior - I'd leave the frame blank it off with a piece of plywood fitted on the inside. You might end up doing more damage to the wall ripping it out.

Answer 4

You want to check and make sure the vent wasn't intentionally left there (I'm thinking like if it was maybe a crawl space air vent so it doesn't get moisture buildup somewhere else if air circulation/flow is blocked)? I have no idea but am also a learn the hard way usually as I go and hate odd, seems so simple to fix....but why Was it left ...especially when installing cabinet or whatever, they already had tools to do it why half ass it...just saying but I'm probably overthinking it since I have no actual training or expertise. Call around and schedule a energy home audit (call elec or gas co. Usually free) and ask their opinion just for reassurance. Good luck and knowledge isn't always power huh...wasn't it nice being ignorant having no idea hole was there in the first place, lol.