Cavity wall recommendations near Edinburgh

[CharlieB]

Hp installation has made it clear that our single -storey 80s extension has no cavity wall insulation.

Before I get lost on Google can anyone recommend either a local contractor or a national contractor who are nice and straightforward?

Also, which is the right / wrong material for it? I remember dampness horror stories but I can’t remember the details. (We’re pretty exposed here so I doubt damp would be a problem.)

Thanks. C

[CharlieB]

No one?

How about has anyone had a bad experience? Ie any contractors to avoid?

C

[Joeboy]

I read up on CWI then did my own insulation while allowing airflow. I'd really like CWI to be a silver bullet but what with the damp issues, cowboyitis and HUGE mortgage problems i think this is too hot a potato to just chuck advice at willy nilly.

I'll throw this out for shooting down. Air circulation in the living space and within the walls is key to the long term health of a building and its inhabitants. CWI can seriously mess with the balance. Have at it!

[resybaby]

My place a 1970's blockrender/block house has CWI, you can see it creeping out the top of the walls in the loft and the injection holes. Its like an offwhite foamy type of stuff that crumbles to dust when you rub it between your fingers. No idea at all what its made from but looks like some sort of injected foam.

Anyway, im frontline coastal on the North Cornwall coast, so very wet and very windy, but ive not noticed anything detrimental for the CWI i have. Not a single sign of damp or mould spores anywhere during the last 12 years.

Not sure if thats anyuse, i suppose a lot of the issues can be down to the installers.

[Joeboy]

Just for additional info, in no way a recommendation. This popped up on my newsfeed today. I had no idea these kits were available.

https://insulation-more.co.uk/products/ ... MEQAvD_BwE

[AGT]

Spray foam worries me interstitial condensation.
Would love to see condensation risk analysis on it,

[jonc_uk]

Just watch with spray foam - there is closed cell and open cell.

I remember 20 years ago when there would be stalls in supermarkets touting spray foam as a 'fix' for your roof. Spraying closed cell foam on the inside of ropey tiles in order to fix your roof. Good for air tightness, terrible for directing any water ingress directly onto your structural timbers without you knowing about it.

Then imagine trying to re-roof with all the old tiles glued in place!

Open cell insulation is more flexible and allows 'breathing' - moisture movement through it. However, in my experience drying timber can shrink away from it - now you have a gap again where you were trying to avoid it.

With retro-fit CWI there has always been the projected fears of damp spots etc. In practice, is this a problem? The wisdom into the 1980s was that it was better to leave the house with a vented cavity to avoid damp problems. However, we all heat our houses more than the 1970s and pretty much everyone has central heating. Houses are both warmer and dryer because of this. The inner walls are naturally more dry.

I spoke to a neighbour who had CWI installed on his 1900 Edwardian detached house which had a finger cavity on the ground floor and solid walls above. This would be a case the usual CWI contractor would avoid. Was it worth it?

He said definitely yes. The house was much warmer.. because it was much less draughty.

And this is my point - on a house with pocketed joists into the brickwork, the suspended floors are vented into the cavity due to the shrinkage of the joists after install. Closing the cavity improves the air-tightness of the house a significant proportion. Less cold air from outside, less draughts, less condensation - warmer and drier house.

As to open-cell foam or poly bead for CWI - not sure.

[Joeboy]

Just watch with spray foam - there is closed cell and open cell.

I remember 20 years ago when there would be stalls in supermarkets touting spray foam as a 'fix' for your roof. Spraying closed cell foam on the inside of ropey tiles in order to fix your roof. Good for air tightness, terrible for directing any water ingress directly onto your structural timbers without you knowing about it.

Then imagine trying to re-roof with all the old tiles glued in place!

Open cell insulation is more flexible and allows 'breathing' - moisture movement through it. However, in my experience drying timber can shrink away from it - now you have a gap again where you were trying to avoid it.

With retro-fit CWI there has always been the projected fears of damp spots etc. In practice, is this a problem? The wisdom into the 1980s was that it was better to leave the house with a vented cavity to avoid damp problems. However, we all heat our houses more than the 1970s and pretty much everyone has central heating. Houses are both warmer and dryer because of this. The inner walls are naturally more dry.

I spoke to a neighbour who had CWI installed on his 1900 Edwardian detached house which had a finger cavity on the ground floor and solid walls above. This would be a case the usual CWI contractor would avoid. Was it worth it?

He said definitely yes. The house was much warmer.. because it was much less draughty.

And this is my point - on a house with pocketed joists into the brickwork, the suspended floors are vented into the cavity due to the shrinkage of the joists after install. Closing the cavity improves the air-tightness of the house a significant proportion. Less cold air from outside, less draughts, less condensation - warmer and drier house.

As to open-cell foam or poly bead for CWI - not sure.

This is an excellent post. In all my wee insulation adventures I've always has a thought towards breathability/vapour release.. I would only consider a sealed envelope type deal if I had mechanical ventilation with automation. Another avenue where wall mounted ashp (inverter air con) systems provide an advantage beyond the cop multiplier? I do agree that we have warmer houses than the 70's/80's but even in our reasonably modern well heated home I run two dehumidifiers in Winter and they are a great benefit. Closed cell and no ventilation is heading one way I suppose.

[kla456]

Maybe going somewhat off-track here but I would not fill any existing cavity wall with insulation, especially foam. The only cavity insulation to be considered is that installed during construction, calculated during the building design. Even that is questionable because we need minimum 150mm (ideally 200mm) wall insulation to achieve Passiv-haus standard for effective heat pump space heating, which can make for very thick walls.

The best way for external walls of existing houses is 200mm external mechanically fixed insulation with acrylic thin-coat render. If there is insufficient roof overhang, then cut back and extend the roof overhang - not easy or cheap. And a whole-house solution is required, together with air-tightness and heat recovery. Many (most) existing houses will never be retrofitted to the 2050 obligation. In this case, better to spend the retrofit money with Ripple and go electric heating with high green energy usage

Messing around with filling the existing wall cavity and other such half-measures is a waste of money and is not good for the building or for its occupants.

Its not cost-effective to retrofit existing houses to Passiv standard (I will never get my investment back), but I have a warm, dry and comfortable low-energy eco house for long-term living.

The market does not yet discount the price of retrofitting existing property to the 2050 obligation. If you are not prepared to retrofit to Passiv standard then better to sell now and buy new that is Passiv standard specced. Or spend big with Ripple.

[Joeboy]

I agree with most of that but not the self fill cavity being a waste of money. I did it on a large internal gable end walled up when the house was extended for the first time. It had no insulation fitted.

Once filled with perlite the difference was palpable. Horses for courses I suppose and general v's specific? I also have a vague memory of an article where a fella had retrofitted his existing house diy style and achieved UK's first passivhaus in the diy retro style. I'll see if I can find him as it was a good read.

Kia, what did you do to your home, was it EWI? Any photos?

This isn't the article but similar.
https://passivehouseplus.co.uk/magazine ... x-years-on