Cavity wall insulation

[stuartpaul]

Given that it's been bloody freezing it's about time I gave CWI serious consideration.

Heard some horror stories about damp after the event and having to remove the outside brick skin to take the very wet insulation out again!

Am I worrying needlessly or are there things to be aware of?

 

[Dibs-h]

Given that it's been bloody freezing it's about time I gave CWI serious consideration.

Heard some horror stories about damp after the event and having to remove the outside brick skin to take the very wet insulation out again!

Am I worrying needlessly or are there things to be aware of?

I think the polystyrene bead stuff would definitely be something to look at - but most installers don't seem to be doing it. Seems to be a prevalence for the fibre (or whatever it is) stuff.

 

[barkwindjammer]

As long as you dont drill holes in the wall to hang stuff :wink:

 

[Dibs-h]

As long as you dont drill holes in the wall to hang stuff :wink:

:lol: :lol:

 

[xy mosian]

Had mine done a number of years ago, three I think. Fibre was used. When I asked about it I was told me it was waterproofed. Of course I asked why? The answer "So that if there is any water ingress it does not form a damp lump but runs down the cavity."

There can be problems if there are any gaps left in the cavity infill. The inner wall surface then becomes a cold spot and attracts all the moisture in the room to condense.

I am no expert that is what I was told. It is the reason buildings with a stone external skin are inspected before work starts. If the stone is not dressed on the cavity surface it is difficult to form a continous filling.

xy

 

[Lons]

Hi
As far as I know, the main problems with breakdown of insulation is pretty old hat and isn't much of a problem these days.

The main reason for damp ingress whether or not you have insulation, is bridging of the cavity during construction. usually mortar droppings on the wall ties which is why modern full / partial fill "cavity bat" procedures elliminates most of that.
Condensation is another problem and I would have though that if an odd cold patch exists, it has to be better than an entire cold wall.

Your external wall will, unless rendered allow water to penetrate in certain conditions. this will run harmlessly down the inside face of the outer leaf unless encountering a "bridge" where it will cross and cause damp patches on the inner leaf. Cavity insulation can hold this moisture but conversly can also reduce the penetration as well.

I've had the poly bead type for 25 years no probs and though have never installed retrospective insulation, I have built hundreds of extensions using the method above in compliance with any regulations at the time.

As an aside, it's worth checking out if you can get a subsidised installation before they pull the funding.

cheers

bob

 

[devonwoody]

We had ours fibre filled 25 years ago but I noticed a few years ago when we had new windows there were quite extensive areas that had no insulation in the cavity.

I suspect that it eventually drops down the cavity to below the DPC and it escapes as dust into the sub floor area where continuous draft then vents it back into the general atmosphere, because where else is it if the cavities are bare?

 

[stuartpaul]

As long as you dont drill holes in the wall to hang stuff :wink:

One may laugh but how does one know when one has poly bead cavity wall insulation?

When one drills a big f*** off hole for the tumble drier vent :shock:

I think the missus thought it hilarious but didn't dare laugh when she saw the look on my face trying to stop thousands of the beads cascading over the floor!! This was of course our previous house.

Thanks for the responses, - I'm indeed looking to get it sorted before grant funding is withdrawn if I can.

 

[xy mosian]

Condensation is another problem and I would have though that if an odd cold patch exists, it has to be better than an entire cold wall.
bob

Apparently the 'odd cold patch' tends to gather more than its fair share of moisture which can lead to a patch of mould. A lot depends upon the surface of course.

xy

 

[Lons]

One may laugh but how does one know when one has poly bead cavity wall insulation?

When one drills a big f*** off hole for the tumble drier vent :shock:

I think the missus thought it hilarious but didn't dare laugh when she saw the look on my face trying to stop thousands of the beads cascading over the floor!!

Been there - done that

I collected it into sacks, climbed into the loft corners and tried to pour it back in - came out looking like a snowman and we were cleaning it up for weeks #-o