Cavity wall insulation advice please

[r6deano]

Morning all,

My bungalows soon to have a new roof, this exposing the wall plates. It's built in '61 and its undergoing a complete renovation, and I want to get my home as thermally insulated as poss. I don't know if it has CWI at present, so my questions are-

1) how do I currently check if there is currently CWI?

2) in terms of installing it - are these schemes you hear and read about worth it?

3) my wall plates will be exposed soon, so is this an opportune moment to fill / check them with ease?

4) what material is recommended for best values?

Tia guys, have a good day

 

[Tigercubrider]

when british gas did a survey of my house, they drilled a series of holes and used a borescope to look.
Then sealed the holes with silicone.

I have tile hung front top floor so drilled my own hole from inside for a look.
I have a Ring borescope.

Lidl or aldi are doing one for around £40 at the moment

 

[JohnD]

CWI installers can be forced to remove it at their own expense if they install it in an unsuitable house. I have noticed British Gas in particular are taking a lot of care to avoid such costs. Presumably other installers are equally anxious to keep their profits up.

I think this is Very Good News.

Hooray for Consumer-Oriented laws which curtail the red teeth and claws of free-market capitalism for the benefit of the ordinary citizen!

(AKA the Nanny State)

Perhaps it'll be the banks next*




*hahahahaha!

 

[Nige F]

I have a Ring borescope.

do you have a speculum too ?

 

[Tigercubrider]

Only on weekends

 

[r6deano]

Only on weekends

Just a thought - if my wall plates are coming off, can I fill it myself/ with my builder perhaps with the beads?

 

[r6deano]

Just FYI..... I've read this article online, whether or not it's worthy advice is up to the reader, but helped to better inform me.

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

personally I'll probably avoid the blown fibre now, and investigate whether I can insulate from internally, plus also install a dehumidifier/ventilation system.

 

[JohnD]

Poor old Jeff has a long-running vendetta against CWI, and some of what he says is very shaky.

For example he claims that a survey of 250,000 properties found that one-third have damp, slumping or missing insulation. He goes on to surmise that half of these are likely to have faulty insulation. However there is nothing in his figures to suggest that is anything other than a guess, nor to suggest that the properties for which surveys were requested are typical of UK housing stock. He makes other guesses about the lifetime of insulation, based on nothing in particular.

In the absence of reliable evidence he admits that "My own opinion is that injecting insulation into an existing cavity wall is a bad idea"

Still, it sells papers and helps him earn a crust.

 

[Doggit]

You can normally tell if cavity wall insulation has been installed, buy looking for holes in the mortar line on the outside of the house. They drill 1" holes every 3 feet or so, and then blow the insulation in, but if they don't blow enough of it, then it's a patchy job, and pretty useless. The other problem with the blown fibre, is that it can carry moisture across on very wet days, and the inside wall becomes cold and damp.

You can't drop the beads down from the top of the wall, as you've no way of knowing how well they've dispersed, and if they flow too well, they'll just come out of any weep holes on the outside, or holes on the inside that haven't been sealed around waste pipes properly.

At the end of it, you're either going to go for external wall insulation (which would be my first choice), or insulated plasterboard on the inside.

 

[theprinceofdarkness]

Insulation techniques short comings:-
1. All rigid foam, internal and external. Mainly that it shrinks, look at the spec, listed as less then 1%, so in a 20' frontage (240") a vertical gap of more then 2" will occur. would help with more layers of foam and sheet overlaps, so gap is not continuos through thickness. fault not fixable. Also difficult to seal joints properly, tape is not heat proof and how long does it last?. U value is good when new and should hold penetrating damp back - is this a problem on a new build?. Also there seems to be no special shapes to go round the corners in cavities or to fix small details around door and window reveals and vents. Cavity fillers are just trims to fill the gap.
2. Blown fibre and beads, reputed to settle, so more can be blown in. Both support damp penetration, fibre worse then beads. As said, beads can find their way out via holes. So will flow to reseal missing areas. Holes should be filled anyway. U value lower then foam. With good workmanship installation will be invisible. Clearly not suitable for some jobs, also top surface needs sealing against draughts.
3. Thin film, used a lot on the continent, the jury is very much out on this stuff, needs a clear air space over it? A step too far for me. The building research heat test ("hot box") are not related to any real life use. Length of life unknown, but as its plastic based, will shrink and the internal layers may degrade..
Frank

 

[JohnD]

reputed ........ may....

 

[Doggit]

Mainly that it shrinks

I think you're referring foam, as opposed to expanded polystyrene. As to no special shapes for corners or detailing, these are cut and created as you go along. I've just done it on a 1930s built property - single skin 11" wall, - and it warms up in about 15 minutes, and doesn't get anywhere near as cold as it used to.

I agree with you on the thin film though; it needs a good loose cavity to allow it to expand and work properly. Where it gets pinned to a batten, then the air gap inside it lessens, and so does the efficiency of it.

 

[r6deano]

Thanks all.

I think I'll go with internal insulated plasterboard then.

My property is currently rectangular, and the Right side is being rebuilt and extending rearward. So just one long length, one short side length and around a third of the other long length are the walls in question - I'll plasterboard thee walls for added protection. No one room will require more than two adjacent sides to be done, so can afford to lose 50-75mm of each rooms measurements .

 

[r6deano]

Poor old Jeff has a long-running vendetta against CWI, and some of what he says is very shaky.

For example he claims that a survey of 250,000 properties found that one-third have damp, slumping or missing insulation. He goes on to surmise that half of these are likely to have faulty insulation. However there is nothing in his figures to suggest that is anything other than a guess, nor to suggest that the properties for which surveys were requested are typical of UK housing stock. He makes other guesses about the lifetime of insulation, based on nothing in particular.

In the absence of reliable evidence he admits that "My own opinion is that injecting insulation into an existing cavity wall is a bad idea"

Still, it sells papers and helps him earn a crust.

Yes I did wonder if 'Jeff' was someone with too much time on his hands after I re-read it..... His stats would surely make retrofitting banned if they were accurate!

 

[John D v2.0]

I think "Jeff" is the Jeremy clarkson of the builder world. Getting old, grumpy, and cynical. But he can make money out of it!
Better attitudes can be found on the green building forum, or many contributors on here too!