Chimney breast ventilation

[bristolben]

Hi

We’re renovating a room with a chimney breast in it.

As it’s an external wall, the plan is to put stud work against the back walls and all the way around the chimney breast, fill with 50mm of celotex and plasterboard it.

This has 2 advantages: (1) it should be warmer and (2) the small cavity behind the studwork (5cm or so) allows me to drop cables rather than chase them in.

The question is whether, if I stick a 9” by 6” vent on the chimney breast, there will be sufficient air flow behind the celotex to keep it dry?

thanks, Ben.

 

[ted456]

Has the chimney breast been opened up at the fireplace and swept and smoke tested?
You could sleeve the vent from the plasterboard surface to just inside the flue ie the vent fascia plate will be visible on the p/b.
What a flue vent has to do with "keeping the celotex dry" i dont understand.

Fwiw:
The plan you are proposing is something that i wouldn't do for a customer unless they signed a disclaimer about any possible future problems.
But, then again, lots of people do similar projects and they seem to turn out OK!

 

[bristolben]

Thanks for the response. It seems like I missed some key details.

The chimney has been bricked up and is not used. It appears to have been this way for some considerable time. Unsure if it was swept before this happened or smoke tested. It’s not used and won’t be again.

When I say “it dry” - I meant the chimney breast, not the celotex. But it’s an interesting point you raise - will behind the stud wall get damp?

My other thought was do to almost exactly as you say, but have the vents in the plasterboard in the alcove section either side.

Does this then negate the effect of putting the celotex in?

 

[ted456]

Read up on the Related Threads below and their related threads to understand more about flues etc.
Behind stud walls have been known to get damp.
A single vent in the alcove is fine.
I dont know what effect the celotex will have.

 

[bristolben]

Thanks - have read most of these.

Conclusion is you always need ventilation, which is fine.

I think my question is, therefore, whether my proposed plan provides sufficient / adequate ventilation for the chimney, or whether the stud is a bad idea!