External Wall Insulation

Marakith

Marakith

Marakith

Associate
Joined
22 Nov 2004
Posts
384
Location
London
Hello!

We're planning a big extension project at the moment, and whilst we've got the "drains up", as it were, we're looking to install a heat pump, solar, and external wall insulation. Our house is a solid brick wall house so it gets really cold in the winter.

We've got a couple of decent quotes in, but they offer 90mm EPS - I know there's potentially an option to go with Kingspan boards instead, but the costs seem significantly higher.

Has anyone done this sort of project before? Do you have any "gotchas" you can share that I should be looking out for?

Many thanks!
 
Marakith said:
Hello!

We're planning a big extension project at the moment, and whilst we've got the "drains up", as it were, we're looking to install a heat pump, solar, and external wall insulation. Our house is a solid brick wall house so it gets really cold in the winter.

We've got a couple of decent quotes in, but they offer 90mm EPS - I know there's potentially an option to go with Kingspan boards instead, but the costs seem significantly higher.

Has anyone done this sort of project before? Do you have any "gotchas" you can share that I should be looking out for?

Many thanks!
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I was thinking the same thing, went to EWI store in Chessington and had a loooooooooooooong chat with the guys who were very helpful.
They basically said get the Kingspan as the difference would be incredible, I ended up not getting EWI and went internal for the remaining walls of my house but from what they said definitely get the Kingspan
 
Deep said:
I was thinking the same thing, went to EWI store in Chessington and had a loooooooooooooong chat with the guys who were very helpful.
They basically said get the Kingspan as the difference would be incredible, I ended up not getting EWI and went internal for the remaining walls of my house but from what they said definitely get the Kingspan
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Thanks!

I've got insulated plasterboard in some rooms but not others. I just had a web-chat with the EWI store guys and the difference between the prices is significant for not a huge difference in performance. EPS 90mm is £8.94 per board for a uvalue of 0.3 and 70mm K5 board is £18.89 for a uvalue of 0.26. So I'll probably go EPS as the improvement over solid walls will still be huge.
 
Lot to consider with solid walls so make sure you go in with all the knowledge you can, adding insulation can cause a lot of problems very quickly to your structure if not done right. Don't forget you'll need to add in vapour barriers etc on the polystyrene which you don't with the celotex/kingspan.
 
I used to work for an EWI company, the best advice is if your planning on staying in the home for 20+ years then it’s only worth having as the payback in heating bills, is minimal.
 
SoliD said:
Lot to consider with solid walls so make sure you go in with all the knowledge you can, adding insulation can cause a lot of problems very quickly to your structure if not done right. Don't forget you'll need to add in vapour barriers etc on the polystyrene which you don't with the celotex/kingspan.
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This is completely right. Solid brick construction properties need to breathe, there’s some really good old home groups, Your Old House UK comes to mind.
 
There is a row of solid brick houses in our town that had external insulation 3 years ago. All partly gov funded. Painted/rendered white. Now every single one is covered in a strange moss/green colour. Owners can't keep it away even after cleaning, very bizarre.
 
Mr.Stu said:
There is a row of solid brick houses in our town that had external insulation 3 years ago. All partly gov funded. Painted/rendered white. Now every single one is covered in a strange moss/green colour. Owners can't keep it away even after cleaning, very bizarre.
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Its the green deal.
 
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Mr.Stu said:
There is a row of solid brick houses in our town that had external insulation 3 years ago. All partly gov funded. Painted/rendered white. Now every single one is covered in a strange moss/green colour. Owners can't keep it away even after cleaning, very bizarre.
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Just standard for render...
 
Mr.Stu said:
Why out of interest? Every other house round here with render on bricks (no external insulation) is fine.
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1. How do you know they are render on bricks?
2. Are you suggesting that damp/low-light can only happen on insulated houses? (that's how algae grows..)?
 
I wouldn’t be using EWI on a solid brick house - the chance of interstitial condensation would put me right off. The whole point of solid brick walls is that they breathe. You are hugely reliant on it being done ‘properly’ and given the level of talent on offer from most of these companies who have jumped on the merry bandwagon of ‘eco measures’ I would frankly run a mile

Sorry to be so pessimistic but unless you know (and I mean KNOW) exactly how it should be done, then I wouldn’t be letting some bloke with his two apprentices turn up and potentially wreck the inside of my house for years to come with frankly no come back
 
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fastwunz said:
I wouldn’t be using EWI on a solid brick house - the chance of interstitial condensation would put me right off. The whole point of solid brick walls is that they breathe. You are hugely reliant on it being done ‘properly’ and given the level of talent on offer from most of these companies who have jumped on the merry bandwagon of ‘eco measures’ I would frankly run a mile

Sorry to be so pessimistic but unless you know (and I mean KNOW) exactly how it should be done, then I wouldn’t be letting some bloke with his two apprentices turn up and potentially wreck the inside of my house for years to come with frankly no come back
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Its fine if you also update the houses ventilation to allow some air exchange to take place to deal with the humidity, just like in any more modern house. You can't just look at insulation one dimensionally which is where people go wrong.

MVHR is the gold standard but there are many ways to skin that cat including good old trickle vents.

Mr.Stu said:
There is a row of solid brick houses in our town that had external insulation 3 years ago. All partly gov funded. Painted/rendered white. Now every single one is covered in a strange moss/green colour. Owners can't keep it away even after cleaning, very bizarre.
Click to expand...

Knock on their door and tell them to just buy a couple of bottles of 'wet and forget' or one of the other equivalent products. Pretty sure Wicks sells the Spear and Jackson version for about £15.

I use it all over to keep things like moss and well any unwanted green algae at bay and it does a good job. You can go several years between applications.
 
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Thanks for all the responses. I'm definitely worried about the damp risk - relating to breathability of the boards/ render. If ventilation can mitigate this, then I'm down with that. I've also noticed some houses around my estate showing algae - and wondered if this was a problem with the render. I understood from the folk at EWIstore that their renders were biocidal and this shouldn't happen.
 
All the houses around my way which are rendered are going green. It’s normal, and highlighted by their solid uniform colour. Brick houses often have a bit of green on them but you have to look closely.

Yes, you definitely need to consider ventilation and that should be a part of the installers remit to consider if there is enough before going ahead.
 
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