Green Building Forum - Filling disused chimney flue

Filling disused chimney flue

Osprey — Sun, 06 Aug 2023 17:15:22 +0100

My house has two unused chimney breasts, one contains two flues ( to ground and bedroom), the other just one flue (to bedroom). The have both been taken down too below roof level, and are open in the loft. The chimneys are of the type that stick out of the exterior wall (rather than projecting in from an inside wall) and hence their tops finish in the eave space in the loft, and are therefor tricky to access, (or even see). There is a vent in each bedroom.

I am goint to have the cavity walls filled, and the roof replaced, and am thinking the latter would be a good time to fill the flues, as I should be able to access them from scaffolding outside.

So, would this be a good idea? Using EPS beads from eBay? Has anybody done this and have a ballpark figure for the amount of beads needed (I will do my own calc. but would like a sanity check! First guess is about 550liters for one full height flue)? Other comments welcomed.

Filling disused chimney flue

tony — Sun, 06 Aug 2023 22:12:26 +0100

EPS beads are a good plan seal the vents and insulate over the top above ceiling level.

Filling disused chimney flue

Osprey — Mon, 07 Aug 2023 09:37:41 +0100

Posted By: tonyEPS beads are a good plan seal the vents and insulate over the top above ceiling level.

Thanks.
I will be using rockwool batts to insulate the top of the inner wall leaf to the roof plate, so I will try and use that for the top as well. I assume no other ventilation needed? (Flues have probably been unused for more than 50 years, and taken down to loft level at least 12 years ago)

Of course there are massive cold bridges around the flues, but not much I can do about those, without ewi (possible future project).

Filling disused chimney flue

Osprey — Mon, 25 Sep 2023 12:26:17 +0100

Well, it's done. One full height (to ground floor) and three half-height (to bedrooms) flues filled with EPS beads. I estimated 15 cu.ft for one full height flue (2.6m ceilings, 250mm square flues), and that was pretty close. The beads flowed much more easily than I imagined they would.

I thought there were only two flues serving bedrooms, but it turned out there was another, unused , one.

Filling disused chimney flue

PeterStarck — Tue, 26 Sep 2023 08:04:07 +0100

Posted By: OspreyWell, it's done. One full height (to ground floor) and three half-height (to bedrooms) flues filled with EPS beads. I estimated 15 cu.ft for one fullmheight flue (2.6m ceilings, 250mm square flues, and that was pretty close. The beads flowed much more easily than I imagined they would.

I thought there were only two flues serving bedrooms, but it turned out there was another, unused , one.

Glad it went well for you. It's a job I've got to do soon. Do you mind telling me where you sourced the beads from.

Filling disused chimney flue

Osprey — Thu, 28 Sep 2023 14:39:52 +0100

Posted By: PeterStarck
Posted By: OspreyWell, it's done. One full height (to ground floor) and three half-height (to bedrooms) flues filled with EPS beads. I estimated 15 cu.ft for one full height flue (2.6m ceilings, 250mm square flues, and that was pretty close. The beads flowed much more easily than I imagined they would.

I thought there were only two flues serving bedrooms, but it turned out there was another, unused , one.

Glad it went well for you. It's a job I've got to do soon. Do you mind telling me where you sourced the beads from.

'Ecobeanz' on eBay. They say the beads come in a stockinette sack. They looked like they were in just a plastic bag, but no - a thin stockinette bag was inside. No problems with static either.