Retrospectively insulating small cavity wall

[jayc89]

We have a relatively small cavity wall section of the house, approx. 15m2 excluding windows/doors. I'm pretty sure it's approx. 100mm cavity and not insulated (built 1970-1980 time). 

Ideally I'd blow EPS beads into it, but I doubt I'll get anyone out for such a small surface area, it won't be worth their time. The only access I'll have is when I replace the windows/doors, and I can't think of a good way of getting some insulation in there without risking the introduction of cold spots.

 

Any clever ideas? 

[Russell griffiths]

Take the doors and windows out and do it yourself. 

[jayc89]

  On 06/01/2025 at 18:58, Russell griffiths said:

Take the doors and windows out and do it yourself. 

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How? Presumably the wall ties would make fitting batts a PITA.

[Russell griffiths]

Blown in beads. 
im sure between us lot on here we can work out how to do it. 
there’s a lad on here the bought a machine to blow in the cellulose type insulation. 
your wall area isn’t large, I’m sure it’s doable. 

[Mike]

If you can connect a hose to a vacuum cleaner exhaust port (as well as the regular hose), that would probably work. Suck in the beads from one end and blow them into the cavity through the other.

[Russell griffiths]

  On 08/01/2025 at 16:35, Mike said:

If you can connect a hose to a vacuum cleaner exhaust port (as well as the regular hose), that would probably work. Suck in the beads from one end and blow them into the cavity through the other.

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My leaf blower would do this nicely. 
the only thing to sort out is some sort of liquid to bond them together. 

[crispy_wafer]

Any use?

[gravelld]

Can you not get access to the eaves, to pour them in?

 

10:1 water:PVA was suggested here: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13384

[jayc89]

Thanks for all the suggestions. It's a flat roof which will need replacing at some point, so I could;
1) Fill up to the bottom of the windows when I change them
2) Fill from the top when I replace the roof

3) Pour some diluted PVA in from the top at the same time

 

Presumably the PVA at 10:1 should be of low enough viscosity to traverse the full wall, top to bottom? 

[richard_scotland]

I filled a cavity wall from the top using beads for a similar sized area of internal cavity wall, which in our case was allowing cold loft air down into the wall. 

 

I just bought some beads from ebay and lots of PVA glue, mixed the glue up in approx 10:1 water:pva in a watering can, then worked up in layers of beads/PVAmixture, pouring from above

 

The beads flowed very well so I had no worries about voids etc, and I could see with a headtorch that all areas were being filled. 

 

If you had two people then you could pour both beads and pva mixture at the same time which would probably work better; I am sure that the PVA mixture in my case didn't quite reach all areas. 

 

Its made a big difference for us, so I think would be well worth doing. I knew it was unlikely we would ever drill a hole through the wall and it wasn't connected to other cavities, so I guess I was a bit more relaxed about how well the PVA mix worked, as long as the beads reached all parts of the cavity (you could foam the top?).