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I am renovating a room in my house and I have come across the hole pictured. It used to be covered by a light wooden box that allowed the air to flow upwards. I was not to keen on it and have taken it down. I would like a nice modern looking air vent in its place. You can see there is a large space to fill, there was loads of rock wool in there when the panel came off. Can I just stick any old vent cover on there? Are there other considerations i need to make? Do I need to re-pack it with rock wool?

Air vent hole

Thanks!

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    It seems that there is direct exterior exposure (sunlight in picture). Ensure you have adequate protection from insects/critters coming in (screen, etc.) Commented May 31, 2018 at 18:02

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You appear to have a hole in your brick wall that vents to the outside. You would like to put a decorative vent grill over the hole and want to know if there's anything, other than aesthetics, to be concerned about.

This hole will leak conditioned air out of your house. The room will be warmer in the summer and colder in the winter. It will also fluctuate with the outside humidity. Almost always this is not what you want.

This hole may leak conditioned air into your wall cavity. From there it will likely find some other path outside or into an unconditioned space such as your attic.

Either air leak is going to reduce comfort in the room and cost a lot of money in heating or cooling bills unless you live in a particularly ideal climate.

Normally when we vent a conditioned space we use a damper so that we can force air out when desired but not get unwanted air coming in. The spring- or gravity-loaded damper would be part of the vent on the outside wall and the inside wall would have a fan. For examples search on "wall mounted kitchen exhaust fan". You need some ducting between the inside and outside so that the vent doesn't simply feed the wall cavity.

Alternatively, if the purpose of this vent is to bring fresh air in then we would reverse the above arrangement to avoid having conditioned air leave the room.

If you are not in need of a vent then I would suggest plugging up this hole. I suspect that the wood box and rock wool you describe was an attempt to do this. Plug up the hole on the inside and the outside so that you don't leave behind a leak into the wall cavity.

[Editing to echo @isherwood's comment.] Before plugging up this hole I would try to figure out why it's there to begin with. You could ask on SE. We'd need more information on where you live, what else is in the room, what's your HVAC system, before hazarding a guess.

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  • I agree on all points. Be sure you need that vent before you recommission it.
    – isherwood
    Commented May 31, 2018 at 19:16
  • Heating is a combi boiler, the house is in Manchester UK. There is no radiator in the room, its the only room in the house that does not have one, I'm beginning think that this ventilation hole is why. Thank you for your answer, at the moment I am thinking the solution is a grated vent and the gap stuffed with rock wool again. if I do get a radiator in this room, this vent might well loose all the heat as you are saying. Commented May 31, 2018 at 20:32
  • A temporary solution may be best while you figure out why the hole is there. You might bring in a pro to get an estimate on fixing it. An experienced local may know why it’s there. Then you can decide whether to fix it yourself or hire the pro.
    – Stanwood
    Commented May 31, 2018 at 20:37
  • Yep, I will enquire with a local tradesperson too. Cheers again! Commented May 31, 2018 at 20:40

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