Patching gaps in cavity wall insulation?

Hoping someone may be able to offer some advice please. Currently renovating the lounge and have removed some old french doors replaced with a window instead. What this has shown though is that the previous owners had cavity wall insulation blown in.

I’m wondering how to fill the void that’s now been created from where we’ve breeze blocked up where the door used to be so we don’t have a void whilst the rest of the room has cavity wall insulation?

We’ve had to go back to brick and replace the ceiling as well as the plaster was too badly blown and there’d been a leak at some point which had meant the ceiling and coving couldn’t be saved. In doing so we found a safe and some missing half bricks which need replacing but these are areas that the cavity wall insulation didn’t reach either.

There’s three large windows in the room and where the lintels are above them there’s also big voids.

So before I fit wood fibre board on the external walls or similar…how can I fill these gaps in the cavity walls? I don’t really want to remove the cavity wall insulation as it isn’t causing any damp issues but conscious I’ll be introducing cold spots if I don’t remedy what I can see.

Thanks

I’d just be using some celotex panels attached to the inside skin with a ~50mm gap between them and the outside face of the brickwork.

Easier to do if you put the internal blockwork up first

Cheers, it’s a very narrow cavity…probably only 50mm so most likely going to struggle to do that.  House was built around 1900-1904.

You could fill some of the gaps by pouring these glass beads in.

It’s inert and will not absorb or wick water.

https://unitylime.co.uk/shop/brand/geocell/expanded-glass-lightweight-beads/

Yeah I would be thinking about the glass bead type stuff. I have used a similar product but different trade name as under floor insulation. It won’t transport moisture. It’s basically a honeycomb structure inside

with only a 50mm gap I’d be inclined to leave it as is – the insulation in the rest of the room will have relatively minimal affect, so the risk of having some gaps is pretty minimal

Thanks all, I’ll have a look at those glass beads.

5lab +1

Double glazing with decent glass is about the same insulation value as an uninsulated cavity wall. Your empty cavity wall is probably better than the original door

You could try a pourable product like Perlite or the glass beads above^^, but that assumes that it won’t migrate sideways.

The bead products have the advantage that if there was a problem you could lift up the cill and hoover it out.

The point about your overall situation having improved by removing the door and installing the window/wall is very valid. Id still try and insulate further if the opportunity arose.

The other voids I would pack in an appropriate insulation, I’ve recently used recycled products that have been pleasant to use. Currently have something called sisaltech , a recycled textile similar to wood fiber but squishy

Oh and go after every draft

You may have considered it already, but would there be any value in adding air bricks in the wall where the door used to be?

I’m assuming it’s a suspended timber floor and the original air bricks will have been rendered inoperable by the retrofitted cavity insulation.

Something to consider before you fill the cavity.