Cavity wall insulation

Byzantium84

Does anybody have any experience with Cavity wall insulation? We were adviced we could get a bit of money off through a scheme to have our walls insulation with closed sell isothane spray foam, apparently it's the best technology out there for cavity walls. We had a survey done, which involved someone sticking a burrosope in the wall, and he said one corner in the dining room needed cleaning out but the rest was fine. I was skeptical of this because I know that the walls have a few damp issues in places, and it's an old house built in 1900 and the brick work isn't great, the outer walls have spalded bricks which are porous and after taking some bricks out in the problem camp corner it turned out to be filled with about 3 foot of old rumble and cement. From a gap 2 foot wide I cleaned out 5 large rubble sacks of old cement and brick rubble. My partner is saying we can clean out the corner and carry on with insulation but I feel like this is such a bad idea. I asked the company to come back and re-assess the walls and they drilled some more holes and tried to tell me it was clean in one part, even though you could see rubble but couldn't tell how deep it was, they drilled some more holes and said it was full of rubble but said it was probably just in that bit. I'm amazed it passed any type of survey and it makes me wonder if they just tell you any old rubbish? I asked what would of happened if they had filled it like that and it caused damp and he said its covered by a 25 year guarantee, so I said 'well what happens if it causes damp and cold spots due to the cavity being dirty? How will you remove the spray foam?' And he said you can't get it out and they would refill it if bits are missing. I don't trust the men at all, they also advised putting sleeves on the airbricks in the loft which British Gas told us we needed to put in for the loft insulation and not to cause excess moisture, so what good would sleeving them do? Anyone else have any experience of this?

phil24_7

Your hunch is right, steer clear.

You cavity should not be bridged by rubble etc and I would definitely not be putting something in the cavity that cannot be removed. There are too many horror stories about cavity insulation causing damp that I would never trust it 100%.

grandma247

The people who are selling this have a vested interest. I have had a few at my door in the last couple of years and I tell them all the same thing. Houses built before 1930 generally should not have cavity wall insulation done it can cause expensive to fix problems and I would not entertain any company that says it is ok to cover any kind of air vent.
Here are a few links to read. I did have a good one saved but can't find it now

https://historicengland.org.uk/advice/your-home/saving-energy/older-houses/insulation/.

https://www.ovoenergy.com/guides/energy-guides/the-ultimate-guide-to-cavity-wall-insulation.html.

https://www.uswitch.com/insulation/guides/wall-insulation-types/.

http://www.neverpaintagain.co.uk/blog/why-cavity-wall-insulation-causes-damp-and-mould/

A dehumidifier is very good for sorting out condensation and it makes the rooms feel warmer. To kill the mould spores I used a steam cleaner. It is a year now and there is no sign of the mould coming back.

FreeBear

My house, a 1920s build which has cavity walls on the lower half, and the upper floor of solid brick had some rockwool blown in to the cavity about 20 years ago. Now wish it had never been done as it has exacerbated some damp issues.

On the bright side, it was a sloppy and slapdash job and it appears that only the first 12-18 inches actually have any insulation in there. For the worst affected area, it looks like I can lift the window boards and get a vacuum cleaner nozzle in there to suck it out. Once that job is done, I'll plug the top of the cavities with thermal breaks.