Isothane Technitherm Cavity Wall Insulation

[SirGalahad]

I have been really undecided on whether to get cavity wall insulation.

It's a 1920's build stone mid terrace with a slate roof with an extension to the rear. There are air bricks in the wall.

Now I have heard scare stories about cavity wall insulation but that was due to the use of wool.

I have had 2 companies out who have said they use Isothane technitherm which is a closed cell foam which will not let water penetrate.

But I thought if the cavity is filled up how will air circulate?

Has anyone any thoughts on this who is actually in the trade or has had this specific type of insulation?

http://www.isothane.com/prod/cavity-wall-stabilisation-and-insulation/

 

[tomfe]

Air bricks are used to ventilate suspended floors not cavities.
The problem with cwi is when it's not suitable it allows damp to track across from the external skin. As long as you get a good survey done and the product is suitable for cwi you should be fine.
Never see this type of insulation being used in 'real' house so can't comment, however I have seen the bonded polystyrene beads and not seen any problems with them.
The pu foam should improve your air tightness etc, I just have visions of it pushing bricks out
America uses it lots as a spray insulator in TFs there has been some reports of it smelling like fish and causing asthma.

 

[^woody^]

But I thought if the cavity is filled up how will cold air circulate?

There we go. The answer's in the question.

 

[^woody^]

I've not seen this type of insulation (expanding foam) for many years, and thought it had been discontinued in favour of fibre or beads.

This injected foam reminds me of many properties that had a similar product injected (albeit a white foam of some sort) back in the 80's, which then experienced persistent efflorescence and salt tide marks to the external brickwork, and a faint but frequent chemical smell inside.

I diagnosed the salt stain to the fact that the foam was keeping the external wall damper than it otherwise should have been. That would seem to fit in with the claims of damp prevention - and being an unwanted side effect

I certainly would not select this product base on its claims of damp prevention. And would steer away from expanding foam unless there is a very good reason to use it in place of other options

 

[SirGalahad]

Air bricks are used to ventilate suspended floors not cavities.
The problem with cwi is when it's not suitable it allows damp to track across from the external skin. As long as you get a good survey done and the product is suitable for cwi you should be fine.
Never see this type of insulation being used in 'real' house so can't comment, however I have seen the bonded polystyrene beads and not seen any problems with them.
The pu foam should improve your air tightness etc, I just have visions of it pushing bricks out
America uses it lots as a spray insulator in TFs there has been some reports of it smelling like fish and causing asthma.

The companies said as its closed cell it won't allow water to spread across and will help if there are any broken wall ties.

 

[Nige F]

It appears from the literature that it is adhesive, i.e helping with broken wall ties. I agree with Woody.