Cavity Wall Insulation

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Discussion

Tlandcruiser

Original Poster:

2,788 posts

197 months

Monday 3rd June 2019
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I’ve just booked an appointment for EON to conduct a survey on my 1960s bungalow. Should I be concerned about cavity wall insulation causing damp issues? I remember reading a lot of issues a few years back.


Equus

16,770 posts

100 months

Monday 3rd June 2019
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It can happen - usually as a result of the insulation highlighting other defects such as mortar snots bridging the cavity, missing or faulty cavity trays or flashings, diabolically bad pointing, etc., and obviously usually worst in areas of high exposure - but it is nowhere near as common with modern, polybead insulation as it was with blown fibre (which will be what most of the horror stories you have read on the internet will have been about).


megaphone

10,696 posts

250 months

Monday 3rd June 2019
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Had my 1930s house done many years ago, never had any issues, noticeably warmer after it was done, heating bills lower.

dhutch

14,198 posts

196 months

Monday 3rd June 2019
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As above comments.

I had it done on my 1938 ex council 3bed semi, at the same time as modern levels of loft insulation, and it made a huge difference to the feel of the place and the heating bills with causing and direct issues. Absolutely well worth it, changed the house, and paid for itself in the 7 years I was there. I kept a sample of the carbon rolled balls in a jar and showed it to potential buyers who as far as i could tell saw it as a positive.

The only indirect issue was that this left the 2ft of sloping ceiling/skelling un-insulated which now being a lot worse than the surrounding caused condensation on that section.

I resolved this in the three bedrooms by room at a time; pulling the plasterboard down, cutting 50mm foam insulation board to go between the 3" rafters, with another 50mm over the rafters, plasterboard over the lot, and skim.
Did everything myself in my own time, bar £100 a room for a plasterer to do the skim. Took about ten hours per room maybe start to finish. Not overly disruptive as it was room by room but obviously more so than the other insulation.
In the bathroom I never got around to it and just treated it to mould spray every 4-6months.


Daniel

Emmapuma

513 posts

198 months

Monday 3rd June 2019
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We bought a 1920's semi which has it installed. The survey that was conducted when we were in the process of securing the mortgage highlighted areas of damp and that it could possibly be caused by the cavity wall insulation. We have been renovating room by room (literally back to bare brick, new stud work round windows etc) and have pretty much sucked the majority of it out. It has solved the damp issues!

Tlandcruiser

Original Poster:

2,788 posts

197 months

Friday 7th June 2019
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Thank you for all your input. Eon came round today and have quoted £644 inc vat. They charge on property type and not m2.


pozi

1,723 posts

186 months

Friday 7th June 2019
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Out of interest what do they use for cavity wall insulation these days only my parents had the mineral wool type fitted to their bungalow and the northern side which gets less sun now suffers from horrendous damp problems which it did not have before?

Equus

16,770 posts

100 months

Friday 7th June 2019
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pozi said:
Out of interest what do they use for cavity wall insulation these days only my parents had the mineral wool type fitted to their bungalow and the northern side which gets less sun now suffers from horrendous damp problems which it did not have before?
For retro-fits its usually 'poly bead', which is basically individual beads of polystyrene foam that are blown into the cavity from holes drilled through the mortar.

In the old days it was 'blown fibre', which sounds like what your parents had done - assuming it was retrofitted - and yes, it was much more prone to damp penetration, as damp could run along the strands of fibre (whereas the chances of it managing to trickle its way across hundreds of little spheres in significant quantity is pretty limited - as I said above, you only tend to get issues with polybead where there is a fairly serious underlying problem and/or the property is in a location with high exposure).

anonymous-user

53 months

Friday 7th June 2019
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I had mine done a few years ago, was the least gain per £ in my case
Cheap extra roof insulation far exceeded the marginal gains from having my walls done TBH

Sheepshanks

32,539 posts

118 months

Friday 7th June 2019
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Tlandcruiser said:
I’ve just booked an appointment for EON to conduct a survey on my 1960s bungalow. Should I be concerned about cavity wall insulation causing damp issues? I remember reading a lot of issues a few years back.
I've got a 1960's house and had it 'surveyed' for cavity wall insulation three times and they won't do it as the cavities are too narrow. Last people were adamant it would be OK but they wanted someone else to check, had a big telephone discussion about, and then said no. The identical house next door to me was done many years ago, with no issues, and it feels much 'cosier' in their house.

Equus

16,770 posts

100 months

Friday 7th June 2019
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Jimboka said:
I had mine done a few years ago, was the least gain per £ in my case
Cheap extra roof insulation far exceeded the marginal gains from having my walls done TBH
You do need to be careful with loft insulation, too - do a search for 'loft condensation' on this forum, to understand why.

Sheepshanks

32,539 posts

118 months

Friday 7th June 2019
quotequote all
Equus said:
You do need to be careful with loft insulation, too - do a search for 'loft condensation' on this forum, to understand why.
Could be "old builder bks" but one I spoke to was dead against retrofitting insulation in houses that weren't constructed for it.

Equus

16,770 posts

100 months

Friday 7th June 2019
quotequote all
Sheepshanks said:
Could be "old builder bks" but one I spoke to was dead against retrofitting insulation in houses that weren't constructed for it.
There are risks and limits associated with it, certainly - you need to be aware of the them and act in moderation.

dickymint

24,101 posts

257 months

Saturday 8th June 2019
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I think you need to weigh up how long it would take to recover your £650 and how much it would cost to put any future problems right.

If you plan to stay put longer than your payback time and it doesn't cause problems then fair enough.
If you try to sell with damp issues it will be picked up and you'll take a hit.

I live in a typical 60's semi, that we have no intentions to move from, and i'm yet to be convinced to get it done.

Equus

16,770 posts

100 months

Saturday 8th June 2019
quotequote all
dickymint said:
I think you need to weigh up how long it would take to recover your £650 and how much it would cost to put any future problems right.
Divided by the probability of actually having problems, if you want to do it right, statistically speaking.

PositronicRay

26,959 posts

182 months

Saturday 8th June 2019
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dickymint said:
I think you need to weigh up how long it would take to recover your £650 and how much it would cost to put any future problems right.

If you plan to stay put longer than your payback time and it doesn't cause problems then fair enough.
If you try to sell with damp issues it will be picked up and you'll take a hit.

I live in a typical 60's semi, that we have no intentions to move from, and i'm yet to be convinced to get it done.
We had a sixties semi done 15 yrs ago. Much cheaper but probably grants available.

The hall felt much more comfortable afterwards, no problems. Next door was also done around the same time, damp patches developed in their hall. They blamed the insulation but other factors came into play too, so not conclusive.

dhutch

14,198 posts

196 months

Saturday 8th June 2019
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Equus said:
For retro-fits its usually 'poly bead', which is basically individual beads of polystyrene foam that are blown into the cavity from holes drilled through the mortar.
This is what I had, from domestic general, before they went bump.

I had a choice of round plain white balls, or silver carbon coated random-oval balls, sprayed with a mild adhesive at the point of entry to the building, which w. 1inch hole drilled in a corner of three bricks.
The latter was about £60 extra and about 10% better on paper, so as I had the £60 and believe in doing it right I went for that. Apparently the had just one silver ball van and something like five plain vans, basically a 3.5ton Luton full of balls, bar a 3ft section for the guys tools, the big hose, and a compressor and adhesive tank.
I came across the balls a couple of times over the following 7years I lived in the house, replacing a window, a missing air brick behind the tiles in the shower, a badly bricked up boiler vent. Each time they stayed put, not signs of slumping or moving, but could also easily by moved if you wanted. It would be faff but I'm sure you could have raked out the whole house with time if you really had to, or a section of a wall.

Had it done to early to get good before and after data on heating costs, but my gut feeling on the data I had was it would have paid back inside ten years with the loft insulation done at the same time. However given the change in fell of the house I would do it again in a heartbeat even if only there a couple of years.

Daniel

Oakey

27,524 posts

215 months

Monday 24th June 2019
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Just had it done today, it was the silver balls. I have to admit, I do worry we'll end up with damp problems or they might have messed something up, guess I'll have to wait until Winter to see.

dhutch

14,198 posts

196 months

Monday 24th June 2019
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Good work. Keep us posted in 6-12months.

shady lee

962 posts

181 months

Monday 24th June 2019
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Oakey said:
Just had it done today, it was the silver balls. I have to admit, I do worry we'll end up with damp problems or they might have messed something up, guess I'll have to wait until Winter to see.
Between that and evohome you should see a large saving this winter mate