External Insulation

bleepandbooster

We have a flat roof /cavity wall extension on our small stone cottage. The cavity was filled with insulation being pumped in a few years ago. The outside render (20yrs old) needs replacing and I was thinking of either K rend or going for external insulation. Would this be suitable or is it only for solid walls with no cavity ?


Many Thanks
David

MX5huggy

You could do external insulation but the benefit would be minimal on an already insulated cavity wall. If you were looking to supper insulate the whole house then OK.

Furts

+1 here. I would not be putting on external wall insulation. I would be pondering on why the render has lasted for only 20 years. As an example, there are countless 1930s houses still with their original render, so why has yours failed? I would wonder if it could be repaired, and if not, then next time ensure that a decent render was applied.

bleepandbooster

Thanks both of you for taking the time to answer. The rest of the house has thick stone walls of nearly 2'. I think the reason for the failure is that it's on red brick.


I was just wondering if there would be any issues with external insulation being used on a cavity wall as it is always promoted for use on solid walls.


Many thanks
David

stator

It's unlikely to be cost effective.

I don't know if it would cause problems. Perhaps if the wall ties needed replacing it might be more difficult/impossible to do it with ESWI ?

Furts

bleepandbooster wrote: »

Thanks both of you for taking the time to answer. The rest of the house has thick stone walls of nearly 2'. I think the reason for the failure is that it's on red brick.


I was just wondering if there would be any issues with external insulation being used on a cavity wall as it is always promoted for use on solid walls.


Many thanks
David

External wall insulation is not used on cavity walls because it requires skilled trades and it is time consuming, expensive and a logistical issue requiring scaffolding for most applications. It is also an area requiring careful inspection - corners are frequently cut and semi trained, or cowboy, installation teams are frequent.

Drilling a cavity wall and pumping insulation is quick, cheap and unskilled so this wins hands down. As with the external insulation there are numerous cowboy crews undertaking this.

It is your choice but I would not give a moments thought to your proposal.

Furts

I meant to add to my above post that if you undertake external wall insulation it is possible that you will invalidate your cavity wall insulation guarantee.

bleepandbooster

Thanks Furts for taking the time to help.


Cofion
David