Cavity wall insulation around an external chimney breast

[Andrew]

A cavity wall insulation installer refused to insulate the cavity wall around my external chimney breast, stating this was their policy for safety reasons. but being unable to provide coherent arguments to back up this assertion. I wanted this area insulated to prevent air movement in the cavity and to minimise the heat lost to the outside from a stove.

I can appreciate dangers may arise if such a job is not done with due care - and this should lead to the flue becoming blocked, but in this case a metal flue liner has been recently installed. Does anyone else have a similar situation - and if so what approach was taken?

It seems to me that the cavity wall installation companies either do not trust the competence of their own staff, or despite their outward "green credentials" are driven by grants and subsidies and in practice only want to "cherry pick" the quickest and easiest parts of the job.

Any comments?

Andrew

[Phil L]

[Phil L]

You won't find a CWI installer to do this, regardless of whether it's a grant job or you are paying full price

I've installed CWI on thousands of homes and never insulated behind a chimney, the reasons are numerous:

1) you aren't going to retain any heat as it's already lost up the chimney. 2) If there's a hole in the flue liner and the whole thing fills with insulation, who's going to pay to have it removed / replaced? 3) cavities rarely go behind chimneys - it's 99% certain that there is no cavity 4) the insulation must go to the top of each elevation, so if the cavity on the chimney protrudes further than the roof line, this would also need to be insulated, who's going to pay for the scaffolding?

5) it's obvious that there is an inside leaf to your outside walls as there's wallpaper stuck to one side of them, who can guarantee that the inner leaf of the cavity is complete inside the chimney?

[Andrew]

Thank you for your informed comments Phil - very helpful..

Andrew