Is cavity wall insulation a good idea?

LeifGR

Sorry if this has been covered; I did a search but could not find an answer.

We were going to have cavity insulation done for our 1982-built house but when I was reading up on the different types available (fibre, foam, beads) I came across this article:

http://www.askjeff.co.uk/cavity.html

This guy is clearly putting forward some powerful arguments against cavity wall insulation. Has this topic been debunked on the forums? If so, could some helpful soul point me in the right direction?

C_Mababejive

There are issues with everything we do but generally,and done professionally, CWI is a good idea and relatively inexpensive.

LeifGR

C_Mababejive wrote: »

CWI is a good idea and relatively inexpensive.

Jeff Howell puts forward a very convincing case why cavity wall insulation is a bad idea.

What specifically is wrong with his statements?

moonrakerz

LeifGR wrote: »

What specifically is wrong with his statements?

He has picked a couple of problems which do happen in a few isolated cases and given the impression that these are major problems that happen with most CWI jobs.

It is rather like saying that people shouldn't used penicillin because a VERY few are allergic to it.

People die in their cars every day - does that keep you out of a car ?

vegasvisitor

We have it in our current house and would be reluctant to get it again.

We feel it has caused a touch of dampness on outside walls (ie have to be careful about putting furniture against the walls).

This may be a regular problem and not caused by the insulation, but I only noticed it after the insulation was fitted. We have been in the house for 8 years and have had the insulation fitted more than half of that time, so maybe I just never had a chance to notice it.

I'm sure some others might be able to comment though?

David_Aldred

Hi LeifGR,
Please have a look at the following thread:
https://forums.moneysavingexpert.com/discussion/comment/27331953#Comment_27331953

As has been previously indicated the majority of installations do not appear to cause major problems but it really comes down to such issues as the type of material used to insulate the wall cavity, the conditions of the wall cavity, height of walls treated, the exposure rating of the property (for instance any property within 8km of the sea is classed as severe exposure by the Building Reasearch Establishment - BRE), how breathable the outer leaf of the cavity wall construction is and any pre-existing moisture resevoirs within the fabric of the building.

When things do wrong they can go wrong in a big way and a house that had relatively dry external walls can change to one where the external walls become very damp indeed with consequential rot. This can occur quickly but sometimes it takes considerably longer such that the client may not correlate the wet insulation with the damp walls until investigation proves otherwise.

Just how common this occurence is I would not like to guess but where I live - close to the sea wet cavity wall insulation is indeed a significant problem resulting in dampness to properties that were previously relatively dry.

In any case I advise anyone thinking of installing such to consider how exposed their property is, the height of walls being treated, what material they are installing (as some appear to be less problematic than others), the condition of the wall cavities, whether the external wall is breathable or say a hard dense render / re-pointing has been applied and one of the most important things, the condition of the cavity wall ties prior to such insulation work.

Addressing corroded cavity wall ties and making good the insulation disturbed when doing such work once the cavities to walls are insulated is far from easy and can result in increased damp problems. You pays your money and you takes your choice - hope this helps, kindest regards David Aldred Independent damp, timber and cavity wall surveyor

LeifGR

@David Aldred: Thanks -- helpful and informative.

My take on this is that many people notice no problems after having cavity wall insulation, but that some do. It also seems that you should go for the more expensive options (taking a day or two to get done and costing upwards of £500) if you want to be more sure that you will not have problems.

One suspects that the firms offering to do the job for £99 will not necessarily be as conscientious with performing all of the assessments of the property in question (well described by David) before conducting the work, nor will they take as much care in performing the work for that amount of money.

A higher up-front cost will obviously change the attractiveness in terms of return on investment. For this reason, because our current heating costs are not astronomical (16,000 kWh) and because we do not want to take the risks outlined by Jeff and David, I think we will refrain from having cavity insulation fitted to our house.

Dry_Rot

It's a shame that you are put off without further investigation. I'd suggest asking one or two more local firms to survey it and raise the questions you have with them so these can be addressed.

When you look into it, the ratio of successful jobs to problem ones is small. Well installed and properly pre-surveyed insulation jobs are extremely low risk.

There are millions of houses with insulation in and a tiny fraction of them give any trouble at all. Most installers get the bulk of their money from local grant schemes, with a small charge to the householder. They have to be qualified and technicians must now have the relevant NVQ's in place.

Dry Rot.

Gizmosmum_2

LeifGR wrote: »

@David Aldred: Thanks -- helpful and informative.

My take on this is that many people notice no problems after having cavity wall insulation, but that some do. It also seems that you should go for the more expensive options (taking a day or two to get done and costing upwards of £500) if you want to be more sure that you will not have problems.

One suspects that the firms offering to do the job for £99 will not necessarily be as conscientious with performing all of the assessments of the property in question (well described by David) before conducting the work, nor will they take as much care in performing the work for that amount of money.

A higher up-front cost will obviously change the attractiveness in terms of return on investment. For this reason, because our current heating costs are not astronomical (16,000 kWh) and because we do not want to take the risks outlined by Jeff and David, I think we will refrain from having cavity insulation fitted to our house.

Anyone charging £500 to do the job is ripping you off not doing a "better" job. The utilities have been forced to subsidise insulation for the last 10 years and everyone pays for this through their utility bills. Companies charging £500 have not got access to this funding - often for good reason ie they don't offer ciga 25 year warranties, they don't meet BBA standards or there have been quality issues with installation or customer care.

The pricing works something like this - cost of installing cavity wall insulation in a bog standard 3 bed semi - £350 - £400 depending on where you live. Utility provides a contribution of between £150 and £300 depending on how close they are to their carbon targets and how depserate they are to meet them. For example there's less money available when they are close to target and you'd expect to pay around £250. When they are short of target the contribution rises and you'll see lots of £99 offer. The cost from the installer is roughly the same throughout although market forces will dictate slightly lower prices when work is slow.

Installation should take about 3 hours for a 2 person team. For more re-assurance you could check out the National Insulation Association who have a code of practice, Energy Saving Trust advice centres 0800 512 012 for free impartial advice or your local authority building control - all of whom have recommended cwi for many years.

Hope this helps - remember paying more doesn't always mean better service or products and certainly doesn't in this instance.;)

LeifGR

Gizmosmum wrote: »

The pricing works something like this - cost of installing cavity wall insulation in a bog standard 3 bed semi - £350 - £400 depending on where you live.
[...]
The cost from the installer is roughly the same throughout although market forces will dictate slightly lower prices when work is slow.

Installation should take about 3 hours for a 2 person team.

Thanks. What I was referring to was this information from the Sunday Telegraph columnist Jeff Howell:

There are two other materials commonly used for cavity wall insulation - foam and bonded polystyrene beads. If properly installed, these materials should theoretically be superior to mineral-wool fibre, as they are inherently waterproof. Neither material is used as widely as mineral-wool fibre because of cost. It can take two or three days to inject a house with either of these materials, and the cost is likely to be several hundred pounds, so they are not favoured by the government-funded schemes (which budget on around œ100 per house for mineral-wool fibre).

(http://www.askjeff.co.uk/cavity.html)
In your post above, were you referring only to fiber-type cavity insulation, or is the Jeff Howell info incorrect?

C_Mababejive

Its about time the UK construction industry moved toward high quality factory made,system build homes instead of glueing baked lumps of clay together on some wind blown building site. That way,we would avoid such issues and have better quality housing

http://www.huf-haus.com/

Nice but im thinking slightly more conservative though similar in design/build.