Cavity Wall Insulation Question

James123_2

I had a reputable company come to install cavity wall installation. Whether this is a good idea or not, there is one further aesthetic issue you might like to consider. The installer began to drill 22mm holes in the wall which not only took out the mortar, but about the same amount of brick as well. I asked the installer to stop and cancelled the installation. The fitters were fine with this & agreed that it would be difficult to blend the 300 plus holes into the brickwork. My understanding was that the holes would only take out the mortar, which is easily remedied. For all others considering such a move, do raise this one issue - you might save £90 on fuel but end up with a house riddled with large calibre gunshot. ASK how big the holes will be and whether they'll be restricted to the mortart only.

Bob63

My house was built around 1910 and has brick-brick cavity walls and floating (timber) floors. When I had cavity wall insulation installed, subsidised by Powergen, the installer fitted new sleeved air bricks to replace the old ones. This was all included in the cost quoted.

If anyone doubts whether it should be done in an older property, our gas bill has dropped significantly and the house is much warmer through the winter.

Mike

ojock

andrew-b wrote: »

So long as you ensure the install of the wall insulation is covered by the CIGA 25 year independent Guarantee you should have no worries as if problems do occur you'll be covered.

I've read several people who have tried to claim off this "25 year Guarantee" and all of them got some letter back saying that damp problem is caused by something else - the guarantee only covers defective parts and labour.

Did you actually get a real surveyor round or was it a salesman who had a quick look round the house? I asked the RICS surveyor who did my house survey before purchase and he told me not to bother with cavity wall insulation.

bathgatebuyer

andrew-b wrote: »

From a legal point of view the RICS building surveyor may have been covering his back..if he recommended you cavity wall insulation and problems arise from an underlying fault he did not spot in the initial survey you might then hold him responsible.

First lesson they gave us on our surveying course - caveat everything!

harryhound

Some older houses, probably pre 1960 , do get problems in the window reveal, which makes the internal plaster next to the window fall off.
The cavity wall has to be sealed where it arrives at the window opening.
This is done by putting a brick or brick bat so that the square head points into the garden and the stretch side goes behind the window frame. The window frame hides the joint.
If this brick is a bit porous it could be allowing water to soak behind the window frame, so it SHOULD have a vertical damp course to stop the moisture getting to the blocks and plaster that make up the inner leaf. If the brick is only a bit porous, the dampness might be evaporating as it tries to track past the 50 mm of cavity.
After the cavity is filled this moisture won't evaporate into the cavity and so might make it into the internal leaf of the wall and start "rotting" the plaster.
After 3 or 4 years the plaster round the window starts falling off the wall.

Only happens in a small number of cavity fills.

eldorado_2

I'm thinking of having the back extension of the house insulated, they're coming round thursday for a look. The extension is around 25 years old and built of blocks, rather like breeze blocks, not sure of the exact type but think they are soild block not the ones with holes in them. Does anyone have any advise of what questions to ask the rep when he's around, if this type of block work could cause problems such as damp or not. The outside of the extension was re rendered about 2 years ago and finished with pebble dash. Is it easy to cover up all the holes afterwards or will I be able to see all the marks long after the work has finished?

harryhound

I would be surprised if your 25 year old blocks are the heavy old dark grey breeze blocks. Someone throwing up an extension that was to be rendered in the 1980's would have been best advised to use 9" solid low density concrete (looks like white or grey "Aero" chocolate inside the block). These days the best practice is to "glue" them together, rather than use a thick bed of mortar. How thick are your walls - they need to be 11" - 12" inches to have a cavity inside?
When the so called "surveyor" comes he will drill some holes to have a look inside - ask to have a squint too, so you can see how "clean" your cavities are. Check that the cavity has been "closed" at the top (It almost certainly has but if not there is a risk that the operative will flood the roof space with overflowing insulation). You may have other leaky holes where pipes and electrical wiring have been punched through the inner leaf.
The guys doing the job are almost certainly to be on piece work (ask!) so agree with the "surveyor" the specification of what they are doing or you risk voids in the cavity. Then make sure the operatives comply with the specification. (personally I would like to see a requirement for the surveyor to come back with a heat imaging camera in mid winter and explain why there are hot spots in the wall!). The three materials all have their pros & cons. I would expect you to be offered "fibre" - looks like cotton buds but needs a bigger hole and a clean cavity (ie carefully laid blocks with a batten on cords to catch the squelched out mortar) if the installation is to be 100% void free.
Make sure the installers come equipped with matching sand and if you can, collect your own pebbles because they too come in different colours and sizes (In my case the installers filled the holes and I poked in the pebbles after swirling them round in a solution of PVA to help them stick).
http://www.screwfix.com/prods/35205/Sealants-Adhesives/PVA/PVA-Sealant-Primer/UniBond-Waterproof-PVA-5Ltr?cm_re=SEARCHPROMO-_-PVA-_-35205#
Slightly misplaced holes makes it more difficult for an onlooker to notice the pattern afterwards.
Be nice to the installers, they are not paid for moving your patio tubs and rambling rose and may be expected to do 4 or 5 jobs per day, so they won't like rendering!.

Let us know how you get on!

rennysnell

A very interesting thread. I've got a detached house, built in 1961, no cavity insulation. I've considered going with the flow and having it done, but then I see negative comments in forums like this and I've now definitely decided against it. I realise there may be many more positive experiences which are not reported, but the problem with cavity insulation is, once it's in, and there's a problem with it, it's to all intents irreversible - practically impossible to remove. I have had two installers quote over the past couple of years; they both said that problems are 'very unlikely' but, if there are, 'you're covered under the CIGA guarantee'. But then you look at forum comments and find almost universal dissatisfaction with CIGA - they invariably say, apparently, sorry, it's a fault with the house. End of story. I would be interested to see statistics of just what proportion of complaints CIGA uphold.

Then there's the question of whether in fact it's effective in reducing energy costs. There are very positive examples in this thread, but there are also people who say it made no difference. For me, if the benefit is doubtful, that's even more reason to avoid the possibility of post-installation problems.

So, I'm giving it a miss. I realise that, amongst other things, this will penalise me in the HIPS report when I come to sell the house, but I will explain to any purchaser why I've not had it done, and point out that they can of course easily have it done, after they've purchased the house; I'll even happily knock off the price of doing it.

dai16

I am interested in installing cavity wall insulation in my 1949 detached house. There is one reason that is making me cautious. I have a number of air bricks about half a metre above ground level all around the outside of my house. These do not vent directly into the inside. There are air bricks upstairs in each of the bedrooms, but again these do not vent directly outside.

Instead it seems that air enters from outside, travels up through the cavity and out through the vents in the bedrooms. One surveyor commented that in my house the vents were allowing the cavity to function correctly and allow it to 'breathe'.

I am therefore concerned about the impact of blocking these, as sleeving would have no effect other than to prevent the insulation from coming out of the vents.

Does anyone else have any experience of this set up?

Ray_Lloyd

I have just had my house cavity wall filled with insulation it was a white cotton wool sort of stuff, they did ask if we had any damp and to my knowledge we are dry (a survayor did check) my question is if at some time it does get water in can the wet insulation be removed, next question regarding the air vent is there anything i can use to defuse the in coming air as last night it was windy and bitter cold and the wind was blowing the curtains about and we where sat in coats scarfs and boots and the heating going full blast.

Ray