Upstairs airbrick

[mike]

I'm renovating the bathroom. Knocking off the crumbling 90 year old plaster has revealed a bricked-up and plastered over air brick inside:

There's a draft around it so I was thinking I'd drag that wooden box out and brick the internal wall up properly.

There's obviously also an external air brick:

It's a cavity wall but the upstairs cavity is narrow and apparently too much so for blown insulation to be added. Downstairs has been done.

What was the reason for these high level air bricks originally? I'm assuming, from the wooden "conduit", it was to ventilate the room rather than the cavity? If this is the case, is there any reason not to seal off the outside airbrick with expanding foam rather than having air blowing into the cavity?

[harry]

In days of yore they believed fresh air was good for you. You often saw this arrangement in bathrooms to get rid of humidity and smells. Even houses of the 1950's had this arrangement sometimes.

Re ventilating cavities. They used to have big air bricks for this in the past. Later it was much reduced. Nowadays the cavities are filled with insulation, sometimes completely,sometimes not. So thinking changed a lot over the years. But read up on vapour barriers.

Still important to ventilate under wooden floors and roof spaces.

[John Williamson]

Mine has this in a bathroom that was recently converted from a bedroom. I don't think the fact that the boiler's in the bathroom is connected with this, as the boiler is room sealed.

1930's house, 2009 bathroom. There are sealed up fireplaces in every room of the house.

[polygonum]

Huh! We've got air vents of about two-brick size in all three bedrooms in a 1970s house - but not the bathroom. Absolutely no need for them - witnessed by my blocking them up on the inner leaf (in a sort-of temporary fashion using some foam around a lump of Celotex) without any apparent change except reduced drafts and heat loss.

[John Williamson]

Wot? No Gaffer tape?

That's what's blocking the current arctic draughts through the one in my living room.

[Ericp]

Crude gas water heaters used to be in bathrooms so you needed an airbrick. Can't remember the name of them, horrible things.

[polygonum]

Often called Ascots. Because that company made them.

[Nick Odell]

Or geysers. Because that's how they behaved sometimes.

Nick

[Ericp]

Ah yes. Thanks :)

(And alive and well in many places it seems.)