cavity wall insulation...

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Maz

Guru
Hi
Has anyone had cavity wall insulation done to their house? How much does it cost roughly?
I think the cost is subsidised by the government, so it may not be as expensive as I think (I'm thinking £100, but you tell me!). Any advice most welcome.
Thanks.
 
It depends on the size and type of the house. I have a 4 bedroom detach and it cost £200 through British Gas a couple of years ago. They also subsidise loft insulation too.
 

Night Train

Maker of Things
I'm still hoping I will get a second chance at cavity wall insulation. It wasn't done when the loft was insulated, twice, as I had holes in the structure that would have let the insulation out.

I might have to finish some building work first though.
 

summerdays

Cycling in the sun
Location
Bristol
I paid quite a bit more than that years ago ... what sort of age house is it? Do you know if your wall ties are in good condition?

I'm looking into this again and managing to get myself very confused by it all.
 
OP
OP
Maz

Maz

Guru
I paid quite a bit more than that years ago ... what sort of age house is it? Do you know if your wall ties are in good condition?

I'm looking into this again and managing to get myself very confused by it all.
Hi
My house is semi-detached. Built in 1945 (so it's 66 y/o). No idea about wall ties - would a house of that age have them? I'm a bit clueless, to be honest.
 

summerdays

Cycling in the sun
Location
Bristol
Wall ties are the bits that hold the inside wall to the outside wall. They are little bits of metal, however the early ones were made out of material that could rust(?) and so they can corrode and lift the bricks. As far as I gather if your wall ties are nearing the end of their life you need to deal with them first before you install wall insulation.
(Take the above with a pinch of salt ... as I'm still learning).
 

Night Train

Maker of Things
If your house is brick built and the bricks look like this, all stretchers, then it will have a cavity.
new.jpg


If your house is very old and has brick work like this, stretchers and headers, then it might not have a cavity.
old.jpg


However, that isn't as reliable. My house was built in 1873 and has that sort of brick bond but the headers are cut headers so it looks like earlier solid wall houses but has a cavity.
The wall ties were orginally wooden lathes laid across the brick skins but are next to useless. Most of my walls have been rebuilt but only the ones I built myself have modern ties in. The wall tie company that did the original work for the mortgage appear to have forgotten to use any on the whole of the front and back walls of the house over three floors!
I am retro fitting them myself. The back wall is done and I still have the front wall and then the side wall of the front room to do.
 

Night Train

Maker of Things
It is possible to borescope the walls to check the conditon of the cavity and the ties. The hole is no larger then that used for filling the cavity.

Filing the cavity doesn't solve all the insulation problems though. Often the cavity isn't clear and can be full of building rubble, mortar that had fallen inside during the build, and that will bridge the cavity causing cold or damp patches.
It is common and possible to clean out the cavities by locating the areas that are bridged, using the borescope, and then removign a couple or three bricks in order to racke out the rubble inside. The bricks are then replaced before the cavity is filled.

An IR camera will demonstrate the before and after effects of the insulation and will also highlight any further cold bridging of the cavity.
 
OP
OP
Maz

Maz

Guru
I took a couple of picture of inside the loft. The 'exposed' wall of the house and the 'shared' wall of the house both have these holes (in 2nd pic, ventilation? breathing?) and you can see the outer wall.
35d6fl2.jpg

Presumably the 'suntanning' on the bricks is from the beams on which the bricks were baked.
674g1z.jpg
 
OP
OP
Maz

Maz

Guru
An IR camera will demonstrate the before and after effects of the insulation and will also highlight any further cold bridging of the cavity.
Some loft insulation companies around here are doing just this...showing an IR picture of your (un-insulated house) next to a house which they have recently insulated (which may or may not be your actual next-door neighbour), so they can get some business off you, hopefully.
 

Night Train

Maker of Things
The colours on the bricks are from the cooking process but you do have a cavity wall there.

Thermal IR cameras are not cheap to buy or hire. This is a random one I found on Google.
You could ask the insulation company if they have one for before and after images. Some do use them to show the job is properly done IIRC.
I remember hearing about some environmental organisations (transistion town groups maybe) loaning the cameras or doing low cost before and after images to help people make the most effective improvements to their homes.
 

Doseone

Guru
Location
Brecon
Your house is cavity - you tell by looking at the stretcher bond to the gable end wall in the loft (not the shared wall with the other semi). The age of the property may mean that your wall ties are on the way out. The first sign will be horizontal cracking to the external leaf of brickwork. The cracking is normally about 18 inches apart, and usually most obvious on the elevation which is most exposed to the prevailing winds and rain. There are plenty of companies that will do boroscope surveys but beware the ones that do it for "free" because they make their money by selling you wall tie replacement. D

Re cavity wall insulation - this is great in new houses where it is built into the construction - but NB there is almost always some form of cavity left. Retro fitting CWI is not an ideal solution as it fills the cavity. The cavity is there for a reason - air is not a bad insulator and the cavity also prevents transmission of damp from the outer leaf of the walls to the inner leaf. If you fill the cavity you have bridged this gap making it far easier for damp to penetrate to the inner leaf.

There are many instances where CWI works fine - but there is a risk involved. The risk increases if you are in an elevated or exposed position.
 
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