Bricking up a fire place...

Andy.T · 2 Jan 2012

I've done some reading on here about this, there are several threads on this I know. But one thing is confusing me a bit...

I know that when you brick up a fireplace you must install a vent to the new wall to prevent sweating, my question though is does this vent have to be on the inside of the house? It's probably a really silly question but could you not install an airbrick on the exterior part of the chimney wall?

Surely, that would prevent draughts in the lounge through the vent? Or would doing that mean that there was increased airflow through the chimney and that therefore heatloss through the walls would be worse?

I want to brick up my chimney, and I want to minimise heatloss through the walls (which is already a problem) but I'd love to avoid having a vent in the lounge wall too.

Any thoughts would be greatly appreciated.

Cheers,

Andy

Geps · 2 Jan 2012

It's normally recommended on the inside as the chimney in most houses backs onto a party wall. If yours doesn't then yes you can.

If it does and you have a suspended wooden floor you can vent it beneath the floor and get the air flow that way (making sure other air bricks beneath the floor are present of course)

Andy.T · 2 Jan 2012

Thanks for that, yes we are detached so it should be doable. My only worry would be that the colder air passing through the flue would increase heatloss through the lounge and bedroom walls.

If we wanted to totally decommission the flue can one fill it somehow? Presumably that would remove the need to ventilate it at all?

Geps · 3 Jan 2012

It would be far easier to just cover it with 50mm Celotex, should stop a large majority of the heat escaping.

Andy.T · 3 Jan 2012

Thanks again, presumably that's just for the old opening in the lounge though? Would there be anything that could be done about further up the flue? We seem to lose a fair amount of heat through the bedroom wall where the flue runs behind.

joe-90 · 3 Jan 2012

How do you know that? What did you use to measure heat loss? And what's this sweating you are talking about?

Andy.T · 3 Jan 2012

Hi Joe,

I used an infrared thermometer to measure the temperature of the bedroom wall at various points. It measured consistently a degree or two cooler on the parts of the wall where the chimney ran behind. So I am assuming that the cold air in the disused flue is drawing heat out of that part of the bedroom wall. The rest of the wall is cavity insulated so I guess it's not suprising the flue part is colder. I just want to do what I can to minimise heatloss in our bedroom really and the flue seems like an obvious route.

Regarding the sweating of the wall, I am not experiencing that at the moment, but the fireplace isn't blocked up yet so I guess I wouldn't be.

I'm just after the neatest (internally), most energy efficient way of decommisioning the fireplace really. But one that, if required, allows sufficient airflow to avoid sweating of the wall (which I've read on here can be a problem).

Cheers,

Andy

joe-90 · 3 Jan 2012

You've got two choices. Either stop the moist warm air of the house going up the chimney or vent it so that it doesn't linger and condense.

I doubt that the fireplace wall will make much difference in the great scheme of things. Terrace house walls are all cold but they are still habitable. I think you are chasing shadows now.

Andy.T · 3 Jan 2012

Fair enough.

Cheers.

diynot

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Bricking up a fire place...

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