cavity wall insulation

[Hard@it]

What are the points against cavity wall insulation ?

[dasherman]

Type 'cavity wall insulation problems' into Google and you get lots of sites that tell you its downsides. Although I've got it and I've never had any problems.

[Hard@it]

Thanks for speedy reply dasherman

[vivandorron]

I'm against cavity wall insulation.

If you have any dirty wall-ties ( those with cement which dropped onto them during the building process) you could end up with damp spots appearing on your inside walls if the cavity is filled. Normaly moisture will bridge the cavity on a dirty wall-tie by capillary action but, because air is circulating within the cavity, it will evaporate before it reaches the inside wall.

Ron.

[Hard@it]

yes, I follow what you are saying, I am not for it, but neighbours are, and I wondered what other people thought.
I would not have it.

[vivandorron]

A good point tonyted. Warm air from the house(or bungalow) gets into the wall cavity and assists with what you rightly describe as the 'thermos' effect.

Good on yer Hard@it for being sensible....best wishes...Ron

[Hard@it]

My reckoning is that the void is there for a reason and no matter what insulating material is used it will do away with the void.
The void is there to prevent condensation and regardless what Manuf/Installers say, if they reckon that air can get through their product then that defeats the insulation factor.

I can understand if when building the house nowadays with even in some cases 300mm inbuilt insul. as part of the design, but this adding to a tried and tested natural anti condensation will not do any good. Furthermore this damp patching and missed areas factors seem to be mentioned a lot.

[Twenty20]

I'm not disagreeing with your final conclusion, but the thermos effect is actually based on having a vacuum in between the two walls, not air.