1950s Ex-council semi, single breeze block wall, how to insulate

richearle

Hi any advice on the best way to insulate the walls? Built from single skin of hollow 9" concrete blocks it's a common type of semi around west norfolk. I think you can inject the hollows with foam (saw a usa guy doing it on youtube) but worried that it will not work well as it won't be a complete insulation layer. On the other hand I read that external insulation can get air circulation in the block hollows carrying heat out into the loft, even before it hits the new insulation. Has anybody any advice on the best way to insulat? I don't want internal as it's too inconvenient. Cheers - Rich

Bendy_House

I can understand the disruption on adding internal insulation, but imo it is by FAR the most effective way to insulate an outside wall.

'Simply' D&D 2" Thermal Laminate Board (insulated plasterboard) to the insides and you will truly transform the insulation value of your home. Even 1" is transformative.

richearle

Thanks for your help Bendy_House. Ok, I'm beginning to come to terms with internal, but it's going to have to be 1". Do I need to do the window reveals? If so can I just ignore the window sill and cover it with new PVC overlay?

FreeBear

You don't have to insulate the reveals. But doing so cuts down on cold spots.

Did a solid brick wall here - Lost about 75mm of floor space once the insulation & plasterboard had gone up. Put 25mm all the way round the window reveal and finished it off with 12mm ply (to replace the ~20mm thick timber). The window board got a 75mm strip of wood fixed to the back so that I didn't have to use nasty looking MDF or uPVC.

That room is now much easier to heat with a smaller radiator. Retains heat a little better. No more cold draughts coming in around the window. And I have nice smooth walls to boot. There will be minimal return on investment through energy savings, but the quality of space is greatly improved.