Very old cavity wall insulation

tanka006

Hi Guys,

Looking for some advice here please.

I have an house that was built in 80's it had its cavity walls insulated when built.

It since had extension's built (before i bought it) these extensions include new Gables, that i guess may not have cavity insulation, but do have attic conversion, that is quite cold.

Also neighbors recall the "white foam stuff" blowing around the place when the extension was being built.

I guess a lot of the cavity insulation came out………..

I have spoken to one local company about re doing new cavity insulation.

They have mentioned drilling the walls & "blowing" out the old stuff & then re doing the cavity - is this crazy?

I just wanted advice as to what to do or ask them about

Thank you

Tanka

MicktheMan

I'm guessing what your neighbour observed ("white foam stuff") was loose aerobead escaping the cavity. If this is the case then it is relatively straight forward to remove the remainder before re-filling with certified bonded bead. And you don't need to blow it out.

I did this myself on my own 1970's house over a weekend. I formed a spout by splitting a 100mm (4" in old money) section of sewer pipe and had very large plastic bags at the ready. I then cored 100mm holes in the outer leaf between the windows approx 100mm above the dpc line. The bead just poured out of the cavity via the spout into the plastic bags. I used a large vacuum to remove the bead below the dpc line. When finished I patched up the holes using the core pieces, sand & cement. I also used an old compact mirror and torch to inspect the cavity to ensure it was fully empty etc.

You may also find after emptying and refilling the cavity that there is little improvement in the heat retention of the house. If so then you likely have an air leakage issue which is not insulation related and adding more insulation is unlikely to address.

tanka006

Hi MicktheMan,

Thank you for your reply. I spoke to my neighbor again after reading your post. it was definitely not aeroboard. it was something pumped escaping the cavity.

He further says that the cavity wall insulation was not bead, but a foam that filled the cavity like beads now & dried in there.

So here i am now with some of the cavity wall insulation gone, new extension with possibly no cavity wall insulation. Gables etc. possibly sheets of aeroboard which was the way it was done here back then - but nobody to yell me what was done..

Could i pump bead around it again?

Would it fill the cavity around anything already done

Thank you

Tanka

MicktheMan

In that case ignore what I said about bead removal. Btw, I didn't mention aeroboard :)

As regards how best to proceed, your 1st step is to ascertain exactly what is in each cavity and have it removed depending. If you have rigid insulation board of some sort, the chances are that it may not have been installed correctly originally (tight to inner block leaf) and will be difficult, if not impossible to remove. This then means that pumping bonded bead into any residual cavity, while physically possible, may well yield little if any improvement to conductive heat loss.

tanka006

Hi MicktheMan,

I am sorry, i read your loose aerobead as aeroboard.

I do know the cavity was pumped, because it was so unusual at the time…….all these holes being drilled seemed crazy.

Also it was not bead - just plain old foam of some sort that dried, but was not hard to break.

Thank you for your responses & taking an interest.

Tanka