Should we go for cavity wall insulation?

[CurrerBell]

We have had quotes for doing this and can't decide whether to go ahead (although we're definitely going to have the loft done).

Since moving in we have replaced windows, rewired, replastered and painted the whole house. I have read that the drilling will cause quite a bit of vibration, and I'm worried about it causing plaster cracks (the house was built in the 1960s and not to a very good standard... e.g. we've had to replace internal walls upstairs which weren't built properly on joists...).

I'm worried that it will be difficult to remove if we get any damp or problems. I'm just not sure I want to take the risk, after what we've been through already with this house!

But, we've just replaced the boiler and it would be lovely to be heating the house more efficiently. It gets very cold as soon as the heating goes off.

If we do go ahead, we are not sure about what the best insulation material might be. One guy was saying they had problems with the bonded beads not filling the cavities properly and possibly causing damp patches (apparently they get stuck going around cobwebs or something?), so they now recommend a new wool product with PVC coating, which can be packed in better. However the other company are saying the beads are the superior product and they charge more money for them. Any advice welcome!

You can get cavity wall insulation done for free usually. Contact British Gas - you don't even need to be a customer of theirs apparently. Worth doing. Made a huge difference to our 1930s house. We have the beads because part of our is difficult to access without scaffolding. The beads could be injected from the corner of the wall.

www.askjeff.co.uk/cavity-wall-fill/

Marking my place as we are considering doing the same but concerned about the damp problems mentioned in the ask Jeff article. Interested to see how others have got on.
Definitely worth approaching British Gas, they are doing our loft for free and have offered cavity wall as well. Not means tested and no strings attached, and you don't have to be a customer.

We have a 1930s semi and got caught cavity wall insulation 8 years ago (beads). The house has lost heat substantially less and is cosier. We also got it done in a house we renovated a few years later. The walls we insulated were external but reasonably sheltered. We've had no issues with damp but I am careful to keep the house warm and not dry washing on the radiators.
Friends of ours in a much more exposed area got cavity wall insulation and regretted it. They live by the sea an the rain and weather is worse there in winter.

To state the obvious: cavity wall insulation is only any good if your house is losing heat through its walls. The best way to find out if this is the case is with a thermal imaging survey which will cost between £100 and £300. The problem with the information given out by the Energy Saving Trust is that they work with averages but there are lots of houses that are outside the average parameters, for example your house could lose far more heat from drafts or if your windows haven't been fitted correctly, than via the walls.

The folks who carry out the thermal imaging survey will usually be able to give your a list of competent contractors who will be able to work out the very delicate balance needed between insulation and ventilation, ensuring you don't have problems with damp/condensation.

Thanks all. I have just contacted British Gas and booked a survey - they said we should qualify for the free insulation (the other companies were going to charge us over £1k for loft and walls!).

I'm not sure how much difference the cavity wall insulation will make. Our house has a lot of glass - large picture windows throughout, and one whole wall of our lounge is glass sliding doors. They are all double glazed and well fitted, however.

Also, we have largish sections of render / cladding at the front and back which seem to have been done on wooden battens with no insulation behind. It all needs to come off and be redone.

I will see what British Gas say re the cavity walls, but after 4.5 years of renovating this house and finally getting the inside to a decent standard, I can't face the thought of plaster cracks, damp etc.

It isn't possible to have a house that doesn't lose heat through its walls.
Unless the outside temperature is hotter than the inside temperature.

CWI installers are responsible to inspecting the walls to verify that they do not have defects (suck as cracked and bubbled render, bad pointing, broken bricks) that might cause them to be wet. Obviously such faults ought to be rectified at the owners expense regardless of CWI, but if the installer is negligent, they can if necessary be forced to remove the CWI at their own expense, usually by vacuuming it out.

Anti-insulation campaigners like to publicise problem houses, but the number is very small.

I am debating this myself. Had the Mark Group round last week who drilled a few holes in my wall before saying they could do it with a grant (no cost to me) which I agreed and I now have 2 weeks ii I want to cancel. I have done the research a bit late but read some horror stories on the internet with damp.

I am in a moderate zone for wind driven rain not in an exposed position and the house is a 60s barratt home. From the survey when i bought the house last year it states about the walls: The internal walls are a combination of solid block work, lightweight timber stud partitions with plasterboard
and skim finish.

The EPC listed cavity wall insulation as one of the recommended steps but not sure how much weight to give to that recommendation.

These government contractors get paid only if they can do it I gather and I heard when they do the job there are time pressures. So they are incentivised to say yes they can do it and to do it as quickly as possible which leaves me worried they will do a botch job. When I asked what material they used they said it's called superfill 40 from a company called knaus:

www.knaufinsulation.co.uk/en-gb/products/blown-mineral-wool/supafil-40-cavity-wall-insulation.aspx#axzz3SBp3x3Ha

says it's moisture resistant but not sure how they measure that.

Anyone else know this material? or have any insight

knauf is a world-class insulation company.

I sometimes hear anti-insulation campaigners claim that insulation absorbs water. I find that puzzling, because I have a glass-wool fill, which I believe is treated with silicone to prevent water absorbtion. I tried holding a handful in a bucket of water, when you lift it out, it is dry.

I've been debating this, cause I'm worried about damp. My parents live in the same build of house, and I find their house horribly stuffy.

How do I find someone to do the thermal imaging thingy? The front of our house is bloody freezing, and would love to know how we can stop this.

I'm actually thinking that it might be better to pay for it, cause I don't trust the guys who are offering to do it free. We had one guy here, and he made such a mess when he was drilling, to test if we needed it - I wouldn't have him do the work.

I'm worried they will just bung it in any old how, since they are not being paid directly by the home-owner - does anyone know if they are still liable to come back and fix anything that they bugger up?

With BG you get a certificate I recall - they have been compelled to spend money insulating homes by the government to reduce energy use.

My parents live in an over-heated stuffy house. It's nothing to do with their cavity wall insulation and everything to do with whacking the heating on and up and not opening windows!

As I understand it, yes. I doubt any sensible person pays for it when British Gas will do it free. Ask, and get it in writing.

I had mine done by my local electricity company, because they have a reputation to maintain and can't go bust or run off. I was perfectly pleased with the job and it made a big difference to home comfort and fuel bills. For example, if I came home at lunchtime in winter, before insulation the house was cold, after insulation it was comfortable.

With my old 15kW boiler, it was unable to keep the house warm on a frosty night, even running at full power. After insulation, the house warms quicker and even the old boiler would shut down and only fire up intermittently.

You can estimate the energy savings by calculating the heat loss twice. Do it once, inputting walls as cavity, no insulation, then save and print the results; then again inputting CWI. Try this Boiler Size calculator which calculates heat loss/heating requirement. calculators.baxiknowhow.co.uk/boiler-sizing/

You may also find that good loft insulation has a good return.

wowfudge
You could be right!

We looked into natural fibres, but they are a lot more expensive.

Can you choose who you get to do it then, PJ?

yes, you can approach British Gas, who install it free in suitable UK homes (ex. NI) even if you are not a customer, or try the large electricity companies, who may have a scheme, especially if you are their customer. Possibly your local authority will have a scheme.

I paid for mine and while I admit to being a bit of a control freak, I also wanted to be sure that I was getting what was absolutely best for my home. I think that the Ask Jeff coloum has overstated the situation, however, some people have had awful problems with CWI and I didn't want to become one of the unlucky few.

The thermal imaging photography/heat loss survey was an absolute eye opener, it showed that the expensive A rated windows I'd paid for hadn't been fitted properly and while I was losing some heat through the walls, it paled into insignificance when compared to the loss from the windows and the unblocked chimney.

The problem with government issued information is that it tends to be a bit broad brush. Most people will make their houses warmer and more energy efficient with loft and CW insulation but a few will get problems with condensation/damp that they never had before. Getting advice from an expert, who has actually inspected your house, makes it much more likely that you will have a successful outcome.

Had it done via Marc group 2 months ago, seem to have done a very good job, and it has stopped/solved a nasty condensation and mould problem in the back bedroom

Oh, and the house is noticeably staying warmer for longer when the heating goes off.

Loft is a no brainer but cavity depends on the area you live in as it can lead to dampness. Don’t worry about drilling cracks though, that’s very unlikely. If you go for it ensure there are no cracks in the outside walls and consider getting them sealed. Various companies such as Cavitech-uk do this effectively.

Thanks all - that's really helpful advice. I'll see what British Gas say and research the options a bit more before (and possibly get an independent survey) before we make a decision re the CWI.

Re the different filling materials... bonded beads seem to be a good option vs rockwool, but I'm confused that one company said they had problems with the beads, and another company said the opposite. British Gas use rockwool (I think) or some kind of expanding foam, although the guy on the phone said it can depend on what is available at the time.

I didn't think expanding foam was still used.

By some weird coincidence, I had a visit today from one of the local companies offering free installation.

They use Knauf Rockwool for loft insulation and Knauf Supafil for the Cavity Wall. I've made an appointment for a survey and will see what they say. Thanks for the advice