EWI DIY

[Jeremy Harris]

14 minutes ago, Mackers said:

Blown cellulose is used widely in America in timber framed buildings. I must do some more research

 

Yes, they have a couple of decades or more head start on us when it comes to using blown cellulose, both wet sprayed and pressure blown (we have the latter in our build).  IIRC, they first started using blown cellulose in the 1970s, a few years before John Larsen came up with the Larsen truss as a way of adding EWI to existing timber framed houses in Canada. 

[Oz07]

49 minutes ago, Onoff said:

 

Not if they do it themselves!

 

Now...where's my trowel & hawk...

Seriously though is it an issue when selling on?

[MarkyP]

3 hours ago, Onoff said:

Talking ballpark here but my external walls are an odd mixture. There's brick & block with a nom uninsulated 60mm cavity, often a mix of brick and block in the same leaf judging by what I found doing the bathroom. I think then I have a 9" block section and also a 9" brick section too. Whatever the wall construction it's all externally rendered. Not sure what's the worst but imagine one of the 9" solid walls. 

 

What nominal thickness of Rockwool should I aim for on a retro fit and what U value should I aim for?

 

Any tables about with what U values for what wall make up?

 

Monkey see monkey do here!

 

Cheers

 

 

I would assume worst case and work on the basis of 9 inch solid walls. graphite EPS is the way to go, better R-value than rockwool. And I agree with @gravelld , rockwool below DPC I think would be a bad idea, not sure I saw any systems which specified it. I reckon it would not like getting damp and would hold water in damp conditions which EPS would not. I remember the wool batts i left out in the rain, went all soggy and took weeks to dry. EPS needed a whack to knock of the water off and wipe and was dry, didn't seem to absorb or hold water to any degree. I think the retrofit standard in EWI work is 90mm or 100mm enhanced EPS to give a BC acceptable u-value of 0.3 over 9 inch solid walls ( you would need thicker wool to achieve the same). But it's relatively cheap to go thicker with the EPS if you can. Where it gets fiddly is at the eaves and gables if the roof doesn't overhang sufficiently to allow the walls to be built out. Also there's a point where the window reveals start to get really deep which might affect visibility and light. I re-roofed so fitted new gable rafters and extended out to allow for the thicker gable walls, and my eaves overhang was already sufficient to allow the EWI. 

 

[MarkyP]

47 minutes ago, Oz07 said:

Seriously though is it an issue when selling on?

no, I don't think so. The warranties are completely worthless in any case. I don't have a warranty, my EWI is fine. 

 

[Oz07]

Anyone listening to radio 4 this morning. Something tells me in future solicitors will want to see a warranty or some kind of building control approval

[MarkyP]

I'm sure it something that a solicitor might pick up on if it's mentioned in the survey or by the buyer. The thing is the warranty itself is largely worthless. I looked at this topic and discussed with system providers. "yes, of course, we provide a manufacturer warranty in case of system failure should you use an approved installer". But the thing is the system never fails, the installation does. I know someone who runs a training centre and covers EWI and knows the industry well. If there is an issue, the system provider will inspect, even drilling cores to assess the build up and will find one of the many issues of installation. Boards with large gaps which were filled with render (can lead to differential drying rates of the render during wet/drying cycles and a grid pattern forming. Other problems such as fixings left too near the surface, inadequate detailing around reveals allowing water ingress, render too thick or too thin, mesh not applied, expansion beads not used as specified, the list goes on. At this point the installer becomes liable, and your redress is via the installer (if they are still in business)

So there's a possibility the solicitor would ask for an indemnity to insure the perceived risk should the EWI not be covered by a warranty. You'd possibly have to educate your buyers. My EWI was done to a very good standard, there aren't any problems  and nor do I expect any. In fact it addressed two big issues with the house. The first was condensation mould in the corners of some rooms. And the second was wind driven rain on a very exposed south west elevation getting across the narrow cavity and tracking over a lintel to the inner leaf, causing significant damp issues. The EWI has fixed both of these problems by providing a very robust rain proof skin and raising the temp of the internal walls so they never reach dew point. 

 

But, yes, I suppose there's a risk buyers may be put off if they don't understand the work and associate it with bad things they have heard about CWI. 

 

EWI is subject to building control. Mine was inspected at various stages and signed off. 

 

 

Edited November 9, 2018 by MarkyP

[Jeremy Harris]

My rather cynical view, heavily influenced by trying to make an NHBC warranty claim years ago, and giving up after a year of legal wrangling, is that all building warranties aren't worth the paper they are written on.  Their only purpose is to satisfy lenders, who have the misguided view that a warranty somehow reduces their risk.  The reality is that I'm near-certain that warranties have no significant impact on the real risk that lenders are exposed to.  I wouldn't be at all surprised to find out that there is a degree of mutual back-scratching going on between lenders that insist on warranties and warranty providers.

[Oz07]

I agree the pieces of paper are worthless just highlighting the fact they come up as a sticking point in conveyancing so often. Is it possible to obtain a warranty on diy installation if your can prove competency?

[Oz07]

The main story was on at 0730 if anyone wants to listen back. Seems mainly down to poor workmanship

[Oz07]

11 hours ago, MarkyP said:

I would assume worst case and work on the basis of 9 inch solid walls. graphite EPS is the way to go, better R-value than rockwool. And I agree with @gravelld , rockwool below DPC I think would be a bad idea, not sure I saw any systems which specified it. I reckon it would not like getting damp and would hold water in damp conditions which EPS would not. I remember the wool batts i left out in the rain, went all soggy and took weeks to dry. EPS needed a whack to knock of the water off and wipe and was dry, didn't seem to absorb or hold water to any degree. I think the retrofit standard in EWI work is 90mm or 100mm enhanced EPS to give a BC acceptable u-value of 0.3 over 9 inch solid walls ( you would need thicker wool to achieve the same). But it's relatively cheap to go thicker with the EPS if you can. Where it gets fiddly is at the eaves and gables if the roof doesn't overhang sufficiently to allow the walls to be built out. Also there's a point where the window reveals start to get really deep which might affect visibility and light. I re-roofed so fitted new gable rafters and extended out to allow for the thicker gable walls, and my eaves overhang was already sufficient to allow the EWI. 

 

Where do you learn what components are nessecary? I.e. Expansion every so often etc etc? 

[MarkyP]

6 minutes ago, Oz07 said:

I agree the pieces of paper are worthless just highlighting the fact they come up as a sticking point in conveyancing so often. Is it possible to obtain a warranty on diy installation if your can prove competency?

I think you are right, it could well become a sticking point if a buyer or solicitor decided they didn't like the look of it. 

 

 I think you'd have to use a single supplier for the whole system and convince them you were competent and had installed it properly. I sourced components from various places, installed the insulation myself, and also found my own renderer but my EWI was largely based on Baumit's ETICS system (I sourced my own EPS and some of the beads). I didn't ask if I could have a warranty but expect the answer would have been no. They did give excellent technical support and visited site.

 

with regard to components, read system supplier documentation. There is also an industry body who publish a best practice document with installation details. Most suppliers follow the same approach which has been evolved in mainland Europe for years.  I based my EWI on Baumit and largely followed their technical installation guidance. After lots of research I found they offered systems incorporating what is considered best practice in all aspects. For example, recessed rather than surface mounted fixings, and frame seal beads around windows, rather than just rendering up to them. But most systems are basically the same and I don't think installation principles would vary greatly if you compared the main system suppliers.

 

EWI has been covered in enormous depth over the years on the green building forum so without wishing to divert people away from this great resource, there is a wealth of insightful discussion there which is worth a read for anyone seriously considering EWI.

[MikeGrahamT21]

For the small amount i've done in EPS (13m2), i'm happy as it is, there is nothing over doorways anyway, so the drip effect isn't an issue, but for any future projects I think i'd lean toward rockwool, even though its not as thermally efficient, there is the added benefits of fire resistance and sound reduction.

[Onoff]

I wonder if there's a hybrid method feasible...EPS/XPS down low, over and below the DPC then Rockwool above.

[oldkettle]

Does EWI need to be notified to building control? I suspect it does and having a BC approval or whatever certificate they issue would certainly help with any future buyer inquiries. 

 

About 10 years ago we were trying to buy a house that was extended nearly 10 years earlier. Planning was in place but it turned out BC completion certificate and any intermediate check information was not. The sellers tried really hard to get one but their BC eventually told them that there was not much they could do as everything was covered and unavailable for inspection. Two banks have refused to issue a mortgage and we had to walk away. Of course EWI is not an extension. 

[Jeremy Harris]

7 hours ago, oldkettle said:

Does EWI need to be notified to building control? I suspect it does and having a BC approval or whatever certificate they issue would certainly help with any future buyer inquiries. 

 

About 10 years ago we were trying to buy a house that was extended nearly 10 years earlier. Planning was in place but it turned out BC completion certificate and any intermediate check information was not. The sellers tried really hard to get one but their BC eventually told them that there was not much they could do as everything was covered and unavailable for inspection. Two banks have refused to issue a mortgage and we had to walk away. Of course EWI is not an extension. 

 

Yes, I believe it does, and may also need PP as well, I think.

[Onoff]

Looks like it comes under the "25% or more" rule imo for a start:

 

https://www.planningportal.co.uk/info/200130/common_projects/18/external_walls/2

[MikeGrahamT21]

On 10/11/2018 at 16:48, JSHarris said:

 

Yes, I believe it does, and may also need PP as well, I think.

 

Definitely needs BC, and be careful as if you renovate a certain amount, you have to do your entire property to current standards, which includes electrics and everything else.

 

PP only required if you are changing the look of the building, if its going to look the same, then no PP required.

[Temp]

On 09/11/2018 at 09:39, Oz07 said:

The main story was on at 0730 if anyone wants to listen back. Seems mainly down to poor workmanship

 

I heard that program. It mentioned a study done by the BRE that examined 2000 houses with EWI and said they couldn't find one to use as an example of good practice!

[Onoff]

@MarkyP, where in your EWI make up is the vcl, if there is one?

[MarkyP]

13 hours ago, Temp said:

 

I heard that program. It mentioned a study done by the BRE that examined 2000 houses with EWI and said they couldn't find one to use as an example of good practice!

they should come and have a look at mine!

 

I think there is a general issue with quality control in large scale schemes where social housing is modernised. I read a surveyor report about issues with EWI seen across multiple installations, it was grim reading but I took some comfort in that the problems were all a result of installation practice and attention to detail, and in some cases product selection. In retrofit you are going to encounter all sorts of potential headaches - meter boxes, flue penetrations, stuff fixed to walls, things abutting or close the walls which would need to be moved or create cold bridges, lack of eaves  or verge overhang - the horror surveys show terrible corner cutting in the approach to these. And then more problems in addition with poor installation of the boards, fixings and render finishes. I guess when you win a contract for an EWI scheme for a large number of homes, finding the skilled labour is very hard, impossible even. 

 

I wouldn't let this put anyone off EWI of their own home, but research carefully good practice and ensure the contractor is skilled and understands the system and its application.

Edited November 13, 2018 by MarkyP

[MarkyP]

9 hours ago, Onoff said:

@MarkyP, where in your EWI make up is the vcl, if there is one?

 

there isn't one and typically one isn't required. 

[Onoff]

15 minutes ago, MarkyP said:

 

there isn't one and typically one isn't required. 

 

Fair enough. I was reading about the Larsen system where he would wrap the whole building in plastic then fit his system over the top.

[MarkyP]

ah, I'm not familiar with the Larsen approach, my comment was in relation to insulation boards fixed to wall and rendered over.