Closing a chimney permanently

Breezer

I have a 1930s mid-terrace house (chimney breast internal, on the party wall) with an open fire in the living room that I don't use. I'd like to keep it for decorative purposes but I don't intend ever lighting it.

I've looked into a few ways of closing it off permanently. The general consensus seems to be to block it off at the bottom in whatever way, put a ventilated cowl on the top, and possibly an air brick in the roof space (opinions seem to differ on the need for this). There also seems to be differing opinions on the need for a vent at the bottom.

However, I rang a company today and was advised that permanently sealing off a chimney that has ever been used is a bad idea, since there's soot in the system, dampness will happen no matter what, and this will cause tar to end up forming and leak out into my room (apologies, my lingo probably isn't correct here, but that was the general gist). They also advised me to light a fire at least once or twice a year to clear the damp out. This company sells products that seal chimneys in a non-permanent way, so I was hoping to hear independent opinions from people that know more than me about this before taking the advice as gospel.

On a related note, I had a builder seal off other chimneys in the house a year ago. He seems to have just blocked the bottom with attic insulation and cement. There's no cowl at the top. So far so good, no dampness, but it's only been a year. Should I be worried? The guy was a perfectionist & charged accordingly so I'd be surprised if he did a cowboy job on the chimney to be honest.

Penn

From my understanding, you need ventilation in the chimney in approx the bottom third. A vent brick in the attic won't get enough air circulation through the chimney, leading to stagnant air in the bottom, increasing moisture vapour and leading to possible dampness.

Calahonda52

Was at a presentation last week where the suggestion is to fill it completely with an inert material such as the stuff made from recycled glass, will get the name later.
Cap it off and seal the bottom.
The argument seems to include it will never get very cold, unless a fully exposed gable chimney

physioman

Calahonda52 wrote: »

Was at a presentation last week where the suggestion is to fill it completely with an inert material such as the stuff made from recycled glass, will get the name later.
Cap it off and seal the bottom.
The argument seems to include it will never get very cold, unless a fully exposed gable chimney

Maybe fill it with vermicilite and put a metal plate at the bottom and cap it off at the top? Only problem is vermicilite will absorb moisture.

Calahonda52

physioman wrote: »

Maybe fill it with vermicilite and put a metal plate at the bottom and cap it off at the top? Only problem is vermicilite will absorb moisture.

they specifically excluded it!

sydthebeat

Yeah, vermiculite would expand wouldn't it...

Ush1

If it's a party chimney shared with the next door neighbour surely you can't go filling it with stuff without their permission?

sydthebeat

Ush1 wrote: »

If it's a party chimney shared with the next door neighbour surely you can't go filling it with stuff without their permission?

if there is not sufficient block separation between the two flues serving the different properties id be extremely worried !!!

theres normally min 215 mm blockwork between party chimneys.

see here:

Breezer

Thanks everyone. I’ve found a guy who comes recommended and specialises in heating and insulation, without selling any one particular product. I’ll throw some of these ideas at him and see what he thinks.

Calahonda52

https://www.dreieck.co.uk/

or
https://www.leca.co.uk

ravendude

Calahonda52 wrote: »

https://www.dreieck.co.uk/

or
https://www.leca.co.uk

How far is the fireplace to an external wall?
If not too far drill a hole in the chimney side to vent and pipe to a drilled hole in the external wall. Tape pipe ends and insulate.

Breezer

Calahonda52 wrote: »

https://www.dreieck.co.uk/

or
https://www.leca.co.uk

Calahonda, is the idea that with these products, you don’t need to vent? Just fill up the whole flue, cap it off and away you go?

ravendude wrote: »

How far is the fireplace to an external wall?
If not too far drill a hole in the chimney side to vent and pipe to a drilled hole in the external wall. Tape pipe ends and insulate.

It’s about 3m. I’ll consider it, thanks.

If I vent it into the room, any idea how this would work with ductless MVHR (which I’m hoping to install in the future?