harry wrote:
On 4 Oct, 23:08, Tim Watts wrote:
On 04/10/10 22:26, Andrew Gabriel wrote:

In ,
writes:
door.

Opening up the cavity is no big deal.

I will need to hold back the existing cavity wall insulation
whilst cutting back. I believe that it will be a wool filled
insulation.

That will probably just stay put.
Be thankful it's not tiny polystyrene balls...

Yes - I can personally confirm that wool (or blown fibre) does not
tend to fall out - much at least. It's worth having a bit of glass
wool to hand (old tank jacket is a good source if there's one down
the tip) and just stuff a bit back as you go. But mostly it is
pretty stable.

Mineral wool cavity wall insulation (blown and bats) are treated with
a moisture repellent to prevent water tracking across the cavity. Get
proper cavity wall bats from your local builder's merchant.
The benifit of opening the cavity is it removes a thermal bridge to
the cavity that would otherwise be left. There is no other advantage.
There is a vertical damp proof course in the brickwork.

I am assuming that the house in question has a vertical dpm of some sort
(built around 1955 but NOT with normal bricks). It certainly has got cavity
wall insulation (installed 11 months ago just in time for cold snap we had).

I would feel happier by opening up the cavity before bricking the hole up.

Cheers
--
Adam