Insulating an unused chimney in old stone cottage

[MikeJH]

I would be very grateful for any advice about insulating an unused chimney. I have a single storey kitchen, which was presumably added to the original stone cottage at a later date, but is probably over 150 years old. This is the coldest room in winter and there are limited options to improve insulation, the loft being well insulated and the floor being solid. The walls are solid stone and 50 cm thick, but the north facing wall has an unused chimney, now bricked over apart from an air brick. The upper end of the chimney ends in the loft just below the roof (there is no longer any external chimney), so it is ventilated at both ends. I am assuming that the reduced thickness of the wall, where the chimney is increases heat loss.

 

Can anyone advise me of the pros and cons of filling the chimney with material, such as blown glass beads or vermiculite with the aim of reducing heat loss through this wall? Will this work or will it invite damp problems due to lack of ventilation? The roof is being repaired at present, so this is an ideal time to have access to the top of the chimney.

 

Many thanks,

 

Mike

[Conor]

Remove the chimney entirely. Sounds like it's not doing anything.

[Mike]

Four choices

- take it down to ceiling level, fill with expanded glass or polystyrene beads (but not with vermiculate, which is hygroscopic), and make it airtight.

- leave it just below roof level, fill to ceiling level as above, seal it airtight at ceiling level and in the room, add an airbrick above ceiling level to ventilate the remaining part in the roof space

- if it's on an external wall and you anticipate it getting damp from rain, etc., fill as above but don't seal it

- demolish it entirely, as Conor suggests. My strong preference.

[Gone West]

On 29/08/2023 at 20:53, Conor said:

Remove the chimney entirely. Sounds like it's not doing anything.

I have a large sandstone chimney breast I would like to remove, but I thought that they were usually structural in old cottages, which is what is putting me off.

[MikeJH]

21 hours ago, Mike said:

Four choices

- take it down to ceiling level, fill with expanded glass or polystyrene beads (but not with vermiculate, which is hygroscopic), and make it airtight.

- leave it just below roof level, fill to ceiling level as above, seal it airtight at ceiling level and in the room, add an airbrick above ceiling level to ventilate the remaining part in the roof space

- if it's on an external wall and you anticipate it getting damp from rain, etc., fill as above but don't seal it

- demolish it entirely, as Conor suggests. My strong preference.

Thanks very much for this advice. It is inside an external 50cm thick, otherwise solid, stone wall, north facing. It is effectively a column of air inside the wall, so option 1 seems to be the best choice, but leaving it unsealed.