Cavity wall insulation

[Serial_Apologist]

This topic has arisen in relation to the 7-yearly re-decoration required to be carried out on our block of 14 flats. The last time it came up, one resident cried out on grounds of cost (to him). Now it seems everyone is seriously giving consideration to agreeing. However, concerns have been raised by two of them with regards to possible obstructions to natural ventilation, possible toxicity in the chemical constituents of the insulation, and there have apparently been reports of damp on inside walls and claims made against installation companies.

What are people's views on CWI? Are there any lessons to be learned from having it?

[Dave2002]

This topic has arisen in relation to the 7-yearly re-decoration required to be carried out on our block of 14 flats. The last time it came up, one resident cried out on grounds of cost (to him). Now it seems everyone is seriously giving consideration to agreeing. However, concerns have been raised by two of them with regards to possible obstructions to natural ventilation, possible toxicity in the chemical constituents of the insulation, and there have apparently been reports of damp on inside walls and claims made against installation companies.

What are people's views on CWI? Are there any lessons to be learned from having it?

There are various forms of CWI. We have experience of two of them. Personally I think that the method with the chemical foam injected into the walls may affect some people - difficult to “prove”, as some people may not be affected much, while others might be aware of the chemicals used afterwards. We had inert material put into our previous house, and this didn’t seem to cause any particular health concerns - or at least none clearly identifiable as being due to the insulation.

Initially we thought that it made the house feel warmer, though we got used to that. It’s not a cure all for cold, but it probably does reduce the heating bills significantly. over time this might offset the installation costs, though it’s not very visible. If there are records of the heating bills over time, it may be possible to compare before and after, though it would take years to establish whether the installation was effective at reducing heating bills.

Some older properties may not have cavities round the whole building. If wanted, different methods of improving the insulation in those parts may be appropriate.

My personal view would be to opt for the inert dry cavity wall filling, rather than any of the expanding foam varieties. Apparently it may need to be topped up after a while, though we never did that.

[robk]

In addition to the concerns about possible toxicity of the fill material there is another worry. Builders are supposed to ensure that excess mortar is cleaned out of the cavity as the wall is built. This takes a degree of care especially around the wall ties. If there is a build up of mortar on or around the ties then cavity wall insulation can increase the risk of capillary movement of water across the cavity leading to damp patches on the inside.

My walls were built in 1875 so I don't have to worry about cavities but the heat loss is an issue (not easily resolved) and there are a number of places where dampness finds a way through.

[gradus]

Our house is getting on a bit and has solid walls that are dry-lined and modern cavity insulated walls, some using foam sheet and some loose fill, luckily neither have given any problems in the last 42 years! My daughter's flat built 10 years ago using supposedly thermally-insulated blocks has had a few problems when occupied by a couple that dried washing in the bedroom and failed to ventilate it properly, but sorted out by the next tenant who has occasionally opened the windows. We also have a small old village chapel in the garden that we've renovated. I decided against adding insulation to the roof/ceiling and the walls to find out whether it could be used in Winter (for teaching) without colossal electricity bills (no gas supply and no oil). Happily it can but I'm spending around £4/£5 a day on electric heating. Plainly this could be reduced by better insulation but not I suspect by a tremendous amount.

[Boilk]

What are people's views on CWI? Are there any lessons to be learned from having it?

Maybe 10 years ago I had those dry little pellets put into the cavity wall - it was a free energy-saving offer where the contractors claim all their costs from central government. No discernable ill effects, and I'm something of a toxophobe (won't invest in a comfy memory foam matress for fear of the chemical off-gassing effects). The first Winter afterwards I did notice less cold, and soon got used to it!

[Serial_Apologist]

This is most helpful, and I am very grateful for people's views and experiences. Thanks!

[Dave2002]

Our house is getting on a bit and has solid walls that are dry-lined and modern cavity insulated walls, some using foam sheet and some loose fill, luckily neither have given any problems in the last 42 years! My daughter's flat built 10 years ago using supposedly thermally-insulated blocks has had a few problems when occupied by a couple that dried washing in the bedroom and failed to ventilate it properly, but sorted out by the next tenant who has occasionally opened the windows. We also have a small old village chapel in the garden that we've renovated. I decided against adding insulation to the roof/ceiling and the walls to find out whether it could be used in Winter (for teaching) without colossal electricity bills (no gas supply and no oil). Happily it can but I'm spending around £4/£5 a day on electric heating. Plainly this could be reduced by better insulation but not I suspect by a tremendous amount.

So that might be about £500 or more per year in heating. I suppose even a small chapel could be large, but I think you’d probably cover the costs of insulation - if not carried to extremes - in a few years, and it could be more comfortable, and might reduce any other problems - such as condensation.

I’m currently trying to evaluate the practicalities and costs of installing more loft insulation. I haven’t reached definite conclusions yet. I am using a thermal imager to locate hot and cold spots. I’m surprised it actually works - through whether it’s telling me anything useful I can’t quite figure yet.

[oddoneout]

At least you won't have quite the same challenges as here?!

https://www.haringey.gov.uk/housing/housing-advice/home-heat-loss/home-insulation/cavity-wall-insulation/high-rise-cavity-wall-insulation

It is quite a complex matter even for individual householders and much more so when agreement has to be reached with others.
The injected foam is the material which I think causes most problems in terms of noxious fumes, and also has the added problem of difficulty(!) in removal if that should prove necessary. The loose fill materials can be sucked out. A potential problem with them is to what extent they settle and leave upper areas less well protected.
Robk mentions movement of moisture across dirty wall ties; another issue there is whether the ties themselves will be damaged by trapped moisture, depending on what they are made of?
This might have useful information https://www.thegreenage.co.uk/can-i-...n-for-my-flat/
and this mentions the Exposure Zones drawn up by the BuildingResearch Establishment. https://www.bbc.co.uk/news/uk-wales-42165358
The involvement of government 'energy saving' initiatives*, and the erosion of effective independent bodies to scrutinise and evaluate building materials and methods, makes it more difficult and time-consuming to get at the facts in my view, but doing the research is the only way to start making the decision. Are there any other similar blocks in the area which have tackled this which you could speak to? Or possibly local authority managed blocks?
There probably isn't an 'ideal' solution, so it's a case of weighing up the pros and cons according to the requirements/limitations of your particular situation and reaching the best compromise.

*Leading to firms more interested in end point payments than suitable solutions and good workmanship, possibly exacerbated, if social housing, by lowest tender decision making. That can make it difficult to separate fault of material/method from fault of installation.

[Old Grumpy]

This topic has arisen in relation to the 7-yearly re-decoration required to be carried out on our block of 14 flats. The last time it came up, one resident cried out on grounds of cost (to him). Now it seems everyone is seriously giving consideration to agreeing. However, concerns have been raised by two of them with regards to possible obstructions to natural ventilation, possible toxicity in the chemical constituents of the insulation, and there have apparently been reports of damp on inside walls and claims made against installation companies.

What are people's views on CWI? Are there any lessons to be learned from having it?

Sorry, don't have any experience to relate, S_A...


... But this is certainly the most exciting thread on What's New at the moment (other than the great unleashed one, of course)


OG

[Dave2002]

Sorry, don't have any experience to relate, S_A...


... But this is certainly the most exciting thread on What's New at the moment (other than the great unleashed one, of course)


OG

There's always the grumble thread .....

[gradus]

Dave, it's about 28x15 and we only switch on fan heaters when lessons are imminent and with large South-facing windows it is surprising how effective the Winter sun can be. Fortunately the piano seems to stand up to it, but with 115 years of experience so it should!

[alywin]

Of course, the whole point of cavity walls is that they should have a cavity in them for insulation purposes. Filling it up may result in damp being able to travel from the outside to the inside of the property, which is not a good idea.

[Serial_Apologist]

Thank you to everybody who has contributed to this thread.

As it turned out, our residents' meeting last month decided not to go ahead with the cavity wall insulation without much prompting from me.

[LezLee]

It doesn't matter now your decision's been made, but I was going to say, don't forget to check with your buildings insurance in case there are any restrictions on what insulation can be used. I was surprised to be asked about it on my renewal form last year.

[muzzer]

So that might be about £500 or more per year in heating. I suppose even a small chapel could be large, but I think you’d probably cover the costs of insulation - if not carried to extremes - in a few years, and it could be more comfortable, and might reduce any other problems - such as condensation.

I’m currently trying to evaluate the practicalities and costs of installing more loft insulation. I haven’t reached definite conclusions yet. I am using a thermal imager to locate hot and cold spots. I’m surprised it actually works - through whether it’s telling me anything useful I can’t quite figure yet.

Dave, what sort of thermal imager/where from? Revisiting my loft insulation is on the todo list this year.