Green Building Forum - insulating a redundant chimney

insulating a redundant chimney

spoonandfork — Mon, 28 Sep 2009 23:32:33 +0100

what's the best insulation material to send down a chimney that is redundant?

I'm taking a chimney down to below roof level then tiling over. It has no fireplace - but I can get easy access to the top.

insulating a redundant chimney

tony — Tue, 29 Sep 2009 00:14:14 +0100

on an internal wall or an external wall?

insulating a redundant chimney

spoonandfork — Tue, 29 Sep 2009 08:06:45 +0100

sorry - external. the chimney forms part of an otherwise solid wall (350mm brick).

insulating a redundant chimney

Nick Parsons — Tue, 29 Sep 2009 08:18:14 +0100

Poly beads? Vermiculite if it isn't heavily exposed. For anything unbonded, make sure you aren't going to have to cop out any spalled bricks in the future (bitter experience! :))

insulating a redundant chimney

spoonandfork — Tue, 29 Sep 2009 08:30:08 +0100

cop out? can you explain?

insulating a redundant chimney

tony — Tue, 29 Sep 2009 09:09:07 +0100

I would fill it with EPS beads.

insulating a redundant chimney

Mike George — Tue, 29 Sep 2009 09:40:45 +0100

I would make sure there is nothing nasty growing in there first. How long have you had the house? Is there any history/signs of wet rot/dry rot? Poorly ventilated [redundant] chimneys are a possible site for dry rot fungi.

insulating a redundant chimney

spoonandfork — Wed, 30 Sep 2009 14:10:17 +0100

Posted By: Mike GeorgePoorly ventilated [redundant] chimneys are a possible site for dry rot fungi.

no history of rot / damp. on external inspection it looks fine. haven't looked down it with a torch yet from above. Assuming a chimney is capped well then it should be fine with EPS beads? In my case, taking it to below roof level so should be very well capped.

insulating a redundant chimney

Nick Parsons — Wed, 30 Sep 2009 20:22:32 +0100

cop out? can you explain?

Spoonandfork. Yes I can! And me an inveterate proof reader. Hangs head in shame. It should read 'chop out'. N

insulating a redundant chimney

spoonandfork — Thu, 01 Oct 2009 20:02:53 +0100

wouldn't eps insulate about twice as well as vermiculite?

insulating a redundant chimney

ChrisPreist — Sun, 28 Feb 2010 10:12:19 +0000

A related question - How much more effective is a properly insulated chimney than use of a chimney balloon/chimney pillow? We are having interior insulation installed throughout our house, and the installer is proposing to fill the unused chimneys with vermiculite for an additional cost of over Â£1000. Given the internal insulation, we are trying to decide if this is a good use of extra resources, or whether just to opt for the cheap option. Thanks.

insulating a redundant chimney

Nick Parsons — Sun, 28 Feb 2010 11:45:35 +0000

Mmm, thinks - despite my earlier comments, if you're dry-lining, why not simply dry-line the chimney breast too? Unless you have enormous chimney breasts, it cannot fail to be cheaper than the quote you have for vermiculite.

insulating a redundant chimney

tony — Sun, 28 Feb 2010 12:35:34 +0000

You would be better to DIY -- I would use polystyrene beads in preference to---- Â£ 1000 he must be an optimist or do you have 100 chimneys?

insulating a redundant chimney

ChrisPreist — Sun, 28 Feb 2010 15:29:44 +0000

Nick, Tony - Thanks. We are already planning on dry-lining the chimney breasts. I believe the proposal to fill the chimneys was primarily to stop draughts from them. That's why I was thinking of the chimney balloons - to stop the air current, but not providing insulation since the breasts will already be clad.

insulating a redundant chimney

tony — Sun, 28 Feb 2010 16:32:01 +0000

what will they do below the floor and above the ceiling? and how with the thermal bridging effect of partition walls be dealt with?

insulating a redundant chimney

rhamdu — Wed, 27 Oct 2010 18:39:18 +0100

I'd like to revive this thread to ask what we should do with our three redundant chimneys.

Demolition isn't an option. Insulation does not seem necessary since the chimneys are on a party wall in a terrrace. I just want to stop draughts. But my mother said chimneys should always be ventilated.

One of the chimneys could easily be connected to the subfloor space for ventilation, and sealed from the room. Any reason not to do that?

insulating a redundant chimney

tony — Wed, 27 Oct 2010 18:50:45 +0100

Yea! then you have turned it into an in-house winter cooling system!!

insulating a redundant chimney

chuckey — Wed, 27 Oct 2010 19:15:47 +0100

What I did with an unused chimney stack was to assemble a BIG wodge of glass fibre in a plastic bag and stuffed it up the flue from an upstairs bedroom, so it was roughly level with the loft insulation. Unfortunately the downstairs flue is some times in use.
Frank

insulating a redundant chimney

docmartin — Thu, 28 Oct 2010 07:37:55 +0100

Tony,
if the subfloor is connected to the redundant gas flue liner and EPS or hydrophobic Perlite poured around that, can you still see any snags?
Thanks, Martin.

insulating a redundant chimney

rhamdu — Thu, 28 Oct 2010 11:02:35 +0100

These chimneys are between our house and another (heated) house. We are insulating over the chimney breasts and party wall in our loft conversion, where there is unheated space behind the party wall. I believe the chimneys will only cause significant heat loss if cold air is flowing into them or warm air is flowing out through them. (Point taken, tony, re dangers of excessive airflow).

I've heard of people stuffing glass fibre or rockwool in their unused chimneys before. I thought the idea was to have something that resists bulk airflow but allows vapour to diffuse. So should it go in a plastic bag?

insulating a redundant chimney

tony — Thu, 28 Oct 2010 13:46:10 +0100

chimneys on external walls may need ventilating but internal ones dont so long as they are ventilated and capped and vented into the loft space

I would pour polystyrene beads down a chimney to ceiling insulation level

insulating a redundant chimney

rhamdu — Fri, 29 Oct 2010 00:51:12 +0100

Posted By: tonymay need ventilating but internal ones dont so long as they are ventilated

sounds like one way or another they're gonna get ventilated

insulating a redundant chimney

docmartin — Fri, 29 Oct 2010 07:40:13 +0100

Thought I should explain why I am considering the complicated option of ventilating the subfloor to the redundant chimney flue(s) in one of my daughter's home; others may be in a similar situation.
The kitchen-diner has had a concrete floor added at some time with no provision for cross ventilation of an adjoining sitting-room; this seems to be common in old housing stock in the UK. A neighbour told us that the sitting room floor had been partialy replaced, due to rot, only a few years ago.
My previous home, circa 1900, had only one suspended floor left unaltered; there was a constant musty smell till I added more air bricks. My present 1930's house has 8-9" ceramic pipes across the solid floored downsairs bathroom and hallway. BTW, caused me considerable problems in the bathroom when putting a thick layer of insulation beneath a new floor to replace the grotty old concrete on earth that the previous owner, a self-employed plasterer, no less, had retiled and upgraded.

insulating a redundant chimney

docmartin — Fri, 29 Oct 2010 07:56:04 +0100

Tony,
in a 1925 solid 9" brick walled house with a triangular chimney breast in a corner on an external wall, could I safely proceed to fill with EPS beads if fitting EWI and removing the stack to leave open in the roof space?
As above, I would also like to put a flexible liner in to ventilate the sub-floor. The other flue, in another room, is internal on a party wall and has an existing flexible liner for a gas fire; soon to be removed when the floor is insulated. I have just realised that I cannot safely put EPS beads in there because I have no control over future use of the neighbours flue. Communicating gaps between flues are common as a legacy of many years of corrosive soot from solid fuel fires,
regards, Martin.

insulating a redundant chimney

rhamdu — Fri, 29 Oct 2010 08:39:39 +0100

Martin, we had the same setup as your daughter. We ended up replacing the rotten timber floor.

We've now got a rather circuitous duct to the rear. For additional ventilation we hit on a solution similar to yours - with the addition of a woodburner inserted between the subfloor and the flue (discussed elsewhere on gbf). Still having problems - smokecontrol area, and the stove we want hasn't got DEFRA approval yet. Grrr.

insulating a redundant chimney

tony — Fri, 29 Oct 2010 08:56:28 +0100

vermiculite is also an option ---- I love the sound of EWI -- why ventilate the subfloor to the roof? it will cause cooling of the house

insulating a redundant chimney

docmartin — Sat, 30 Oct 2010 00:19:00 +0100

Tony,
Redundant, tall, single chimney stack best removed as will need re-pointing, or more, eventually. By doing this I could provide:-
1 cross ventilation the the external corner of the side blocked by the concrete floor in the kitchen
2 An unobtrusive route for a duct from a central mechanical extract (CME) next to the cooker
3 " " " a cable, sheathed against EPS, if used, for the boost function
4 Less infiltration to the sitting room into the redundant chimney
5 EPS/Vermiculite around the extract duct will stop condensation as the warm kitchen air reaches the cold roof.
Ventilation ducts are a problem in refurbs. I recently read about unsightly plywood boxing in 'Retrofit for the Future' projects costing well in excess of Â£100,000!
My other concern is the effect of possibly damp subfloor air reaching the roof space. The roof is unfelted Welsh slate torched with lime mortar; in very good nick for 85 yrs old but no formal ventilation - as yet.
I will, of course, add to the airbricks but these would still only be on the N & E sides of the room. Perhaps sufficient and leave out the ventilation duct to the roof space if a step too far into the unknown?
Thanks for your comments, Martin.