Cost of installing EWI??

[Adsibob]

Received the quote from my builder for supply and installation of the 40mm K5 Kooltherm onto the external wall of my house. There is 114m² to do across three facades: back, front and rear (it's a semi detached house). 

The quote is to supply and install it and apply a "base coat" ready for subsequent rendering, but does not include the rendering itself. The substrate it is being applied to is mainly 1930s brick which we recently uncovered (previously it was covered with pebbledash) and there are around 9 windows which will need to be navigated. It's come in at a whopping £6k plus VAT. Given the 40mm Kooltherm itself will cost about £21.10 per m² plus VAT (including 10% extra for wastage), the labour is coming out at £3,594.60 plus VAT, or £31.53 per m² which seems high to me although the K5 boards are not huge (1200x400).

 

I am having the same builder also re-roof the whole house, so I do not think the above costs include scaffolding because I am already paying for scaffolding for the roof, unless to re-roof a whole roof of a semi detached house one doesn't need side scaffold access and only needs scaffolding at the rear and front, in which case the above might include the additional scaffolding required to do the side of the house.

 

Meeting with my builder tomorrow to go through the latest set of extras (of which this is the only real surprise) and would be helpful to get people's views on the reasonableness of this quote and whether scaffolding would in any case have been needed on the side for the roof or whether the roof could be done with just scaffolding on the rear and front. I will obviously ask him about the scaffolding, but wanted to see the lay of the land here first.

 

Many thanks!

Edited July 12, 2021 by Adsibob

[Conor]

As somebody that's doing their own EWI on a new build ICF house... I'm not surprised. It's a time consuming job that needs a fair bit of care and attention. I wouldn't so it for less that that.

 

Can you use thicker insulation or will it less with your reveals/soffits? As you can see material cost is low, so you may as well go for thicker if possible.

Edited July 12, 2021 by Conor

[Dudda]

It it time consuming and that price is about right. As Conor said above I'd seriously consider using thicker insulation if you can. If the area is tight and you can only fit the 40mm on one elevation I'd still consider increasing the thickness on the remaining elevations. The cost of materials will only go up a bit but labour shouldn't. 

[Adsibob]

Thanks for your comments, that is reassuring. 

With insulation, obviously the more we can put in, the better, but unfortunately there is a limit before we start to ruin the architectural features of the house. It's a 1930s semi, and whilst replacing all the windows has given us some play with the reveals, there isn't anything we can do about the soffits. 

I'm putting a LOT of insulation in the roof and the whole of the ground floor will be upgraded to an insulated slab, and we are fitting MVHR and brand new thermally broken 2G windows everywhere so I'm hoping overall we will dramatically increase the energy efficiency of the house.

[tanneja]

Have you applied to have the EWI cost part covered by the Green Home Grant scheme?  Unsure if still running.

[Adsibob]

3 minutes ago, tanneja said:

Have you applied to have the EWI cost part covered by the Green Home Grant scheme?  Unsure if still running.

No. I tried, but unfortunately that Scheme was a total joke. Impossible to use and I believe was  withdrawn at the end of March. Pathetic government bureaucracy. They should have just zero rated all Green goods, such as insulation, and then given people a cheque for a couple of £k upon showing an improved EPC certificate. Would be so much easier than that stupid scheme.

 Our house was rated “D(56)” when we bought it, but I think we will hopefully get it up to a “B(85)” or slightly higher.

[SteamyTea]

1 hour ago, Adsibob said:

 

I am having the same builder also re-roof the whole house

Have you looked into fitting roof integrated PV. Similar price to some roof coverings.

[Adsibob]

Just now, SteamyTea said:

Have you looked into fitting roof integrated PV. Similar price to some roof coverings.

Already bought roof tiles. Next life.

[SteamyTea]

5 minutes ago, Adsibob said:

. Next life.

Sell them, they are in short supply.

[SimonD]

7 hours ago, Adsibob said:

Received the quote from my builder for supply and installation of the 40mm K5 Kooltherm onto the external wall of my house. There is 114m² to do across three facades: back, front and rear (it's a semi detached house). 

The quote is to supply and install it and apply a "base coat" ready for subsequent rendering, but does not include the rendering itself. The substrate it is being applied to is mainly 1930s brick which we recently uncovered (previously it was covered with pebbledash) and there are around 9 windows which will need to be navigated. It's come in at a whopping £6k plus VAT. Given the 40mm Kooltherm itself will cost about £21.10 per m² plus VAT (including 10% extra for wastage), the labour is coming out at £3,594.60 plus VAT, or £31.53 per m² which seems high to me although the K5 boards are not huge (1200x400).

 

I'd approach this very carefully. EWI takes a lot of care to detail properly and I'd be surprised if a general builder knew the detailing requirements - it's bad enoug finding an ewi company that really knows what they're doing. I think the prices you've been quoted might be on the cheap side. Last time I got a complete figure it worked out to about £75/m2 plus VAT by an EWI company. This was 4 - 5 years ago. Recent figures I've heard from other it's been up to £100 labour and materials.

 

Some of the things the consider:

 

Old substrates where old render has been removed may need a levelling coat before installing the EWI to avoid excessive voids behind that can lead to unwanted convection. Windows and other openings are a bit of a pain as you need to ensure no joins are in line with the corners, so it's a bit like a game of tetris. Then you have the detailing around the reveals that need to be done with care to prevent cracking and water ingress. If your reveals are to be 40mm as per your insulation thickness, you're going to struggle to include both a corner bead and apu rail - the rail that seals the render and ewi against the window frame - so you will have to look at some alternative detail as just using silicon is not best practise). Are you having plinth insulation installed below dpc? If so, what is the cost of the usually specced xps, rendering and ground detail? How is the builder suggesting you deal with service openings and runs - e.g. soil pipe, guttering, waste pipes, gas/electricity meter box, and any phone lines/electricity cables. And that's just the beginning.

 

Also keep in mind that Kooltherm is not vapour permeable so you'll need a careful look at moisture and condensation management to the interior of your walls. EPS would be better as it's considered to be semi-permeable, so better than none. Rockwool ewi possibly even better on this front. Anyone looked at your condensation risk for your proposed ewi?

 

Overall, I think you'd be better off finding a dedicated EWI installer to do the whole job including the final render. That way you'll be more likely to also qualifiy for the manufacturers system guarantee too - whatever that may be worth ? At present you run the risk of multiple parties blaming each other if there's a problem down the line - not unheard of with poorly installed thin coat EWI.

 

Sorry if I've put the cat amongst the proverbial...

Edited July 12, 2021 by SimonD

[oldkettle]

2 hours ago, SimonD said:

Last time I got a complete figure it worked out to about £75/m2 plus VAT by an EWI company. This was 4 - 5 years ago. Recent figures I've heard from other it's been up to £100 labour and materials.

 

Was it including rendering? I remember getting a similar estimate for a 100mm ewi with render. 

[SimonD]

5 minutes ago, oldkettle said:

 

Was it including rendering? I remember getting a similar estimate for a 100mm ewi with render. 

 

Yes, that's with render finished.

[Adsibob]

3 hours ago, SimonD said:

 

I'd approach this very carefully. EWI takes a lot of care to detail properly and I'd be surprised if a general builder knew the detailing requirements - it's bad enoug finding an ewi company that really knows what they're doing. I think the prices you've been quoted might be on the cheap side. Last time I got a complete figure it worked out to about £75/m2 plus VAT by an EWI company. This was 4 - 5 years ago. Recent figures I've heard from other it's been up to £100 labour and materials.

 

Some of the things the consider:

 

Old substrates where old render has been removed may need a levelling coat before installing the EWI to avoid excessive voids behind that can lead to unwanted convection. Windows and other openings are a bit of a pain as you need to ensure no joins are in line with the corners, so it's a bit like a game of tetris. Then you have the detailing around the reveals that need to be done with care to prevent cracking and water ingress. If your reveals are to be 40mm as per your insulation thickness, you're going to struggle to include both a corner bead and apu rail - the rail that seals the render and ewi against the window frame - so you will have to look at some alternative detail as just using silicon is not best practise). Are you having plinth insulation installed below dpc? If so, what is the cost of the usually specced xps, rendering and ground detail? How is the builder suggesting you deal with service openings and runs - e.g. soil pipe, guttering, waste pipes, gas/electricity meter box, and any phone lines/electricity cables. And that's just the beginning.

 

Also keep in mind that Kooltherm is not vapour permeable so you'll need a careful look at moisture and condensation management to the interior of your walls. EPS would be better as it's considered to be semi-permeable, so better than none. Rockwool ewi possibly even better on this front. Anyone looked at your condensation risk for your proposed ewi?

 

Overall, I think you'd be better off finding a dedicated EWI installer to do the whole job including the final render. That way you'll be more likely to also qualifiy for the manufacturers system guarantee too - whatever that may be worth ? At present you run the risk of multiple parties blaming each other if there's a problem down the line - not unheard of with poorly installed thin coat EWI.

 

Sorry if I've put the cat amongst the proverbial...

So the builder does hold himself out as experienced in EWI. All his marketting material states this, and whilst I'm not one to fall for marketing material, all of his work to date (which has covered many different things) has been very good quality with lots of attention to detail. EWI has been around for a while and so has he, so I get the feeling that he's done it many times before. But the questions you raise are helpful and I will ask him these before I commit.

 

As for condensation risk, yes the whole build up, internal and external, has been designed by a specialist RICS surveyor with input from Tyvec/DuPont who are the manufacturers of the internal breathable vapour membrane. We are letting the wall breath on the inside rather than on the outside. There is also an internal MVHR system so that too will minimise the risk of condensation.

 

Gutterings aren't a problem because we are installing everything new, so it will go over the EWI. As for soil pipes, the holes for these will need to be drilled through the EWI, but there is only two places where this will be done, and I assume he will have a detail for keeping it water tight I will ask.

 

No idea what plinth insulation is, so I will ask about that too!

[Adsibob]

So discussing this further with a RICS surveyor who is helping us with some of the trickier design elements, he has recommended to go 15mm thinner on the insulation that is below the DPC so we can have a drip bead. Basically this:

 

 

What are people's thoughts on this? The pro is one keeps the area of wall underneath the DPC drier, whereas the downside is that we have less insulation there, though not that much less.

[saveasteading]

Green Home Grant scheme?

 

Rather than split this discussion, I will start a new thread.

[SimonD]

16 minutes ago, Adsibob said:

So discussing this further with a RICS surveyor who is helping us with some of the trickier design elements, he has recommended to go 15mm thinner on the insulation that is below the DPC so we can have a drip bead. Basically this:

 

 

What are people's thoughts on this? The pro is one keeps the area of wall underneath the DPC drier, whereas the downside is that we have less insulation there, though not that much less.

 

I haven't looked at the link but that's about right - that is what plinth insulation is. Basic buildup illlustration, from ground: gravel, plinth insulation, expanding foam tape on top of plinth insulation, starter rail at dpc, then your normal ewi.

 

Plinth insulation thickness should indeed be reduced. IIRC, i read a rule of thumb figure that it's thickness is determined by either 75% of thickness of ewi or 75% of the ewi thermal insulation figure - can't remember which right now and don't have acces to the relevant paperwork right now. Either way you get a drip at the bottom of your main ewi at dpc.

[Marvin]

Adsibob, bit of a side issue. When we were renovating our home we were advised to keep the EPC assessor informed of the progress so the assessor can inspect /confirm insulation, espically where insulation was more than the minimum for Building Regulations. 

 

Expect you've got this covered.

 

Best of luck.

 

Marvin.

[Adsibob]

56 minutes ago, Marvin said:

Adsibob, bit of a side issue. When we were renovating our home we were advised to keep the EPC assessor informed of the progress so the assessor can inspect /confirm insulation, espically where insulation was more than the minimum for Building Regulations. 

 

Expect you've got this covered.

 

Best of luck.

 

Marvin.

Thanks Marvin, but I'm a bit confused. In England an EPC is only required when one rents or sells one's home. At that point you pay an EPC assessor to come and assess it and what he or she isn't able to prove, they generally take your word for it but add "(assumed*)" and the asterisk explains that this is assumed because they weren't able to verify it. Are you suggesting I could avoid the assumptions and actually get it verified? I'm not planning on selling for MANY MANY years after all this stress and heartache, so apart from when I do sell, why else would I need an accurate EPC?

[Marvin]

1 hour ago, Adsibob said:

Thanks Marvin, but I'm a bit confused. In England an EPC is only required when one rents or sells one's home. At that point you pay an EPC assessor to come and assess it and what he or she isn't able to prove, they generally take your word for it but add "(assumed*)" and the asterisk explains that this is assumed because they weren't able to verify it. Are you suggesting I could avoid the assumptions and actually get it verified? I'm not planning on selling for MANY MANY years after all this stress and heartache, so apart from when I do sell, why else would I need an accurate EPC?

Yes you are right. Renting, selling or to take up some of the green deals, you would need to have an EPC. So if you never want any of those then I guess your ok.

 

And yes, if you were wanting verified insulation layers then an EPC inspections when building should give you verification, however on the ASHP deal they would only accept an EPC less than 2 years old.

 

So you just crack on.?

 

M.