EWI DIY

[Onoff]

Any pointers on ballpark per m2 figures if one was to fit EWI on a DIY basis at today's prices? 

 

Also particularly interested as to the detail below ground, how the ewi bridges the dpc etc if the property is of traditional construction on concrete footings.

 

Thanks

[Dreadnaught]

(For those others like me who did not know what EWI stands for I think it is External Wall Insulation. I had to look it up!)

[gravelld]

Well you can get prices for the materials by going to somewhere like EWI Pro, if that's what you mean?

 

Take a look at https://retrofit.support/category/EWI-GL/

[Onoff]

48 minutes ago, Dreadnaught said:

(For those others like me who did not know what EWI stands for I think it is External Wall Insulation. I had to look it up!)

 

When I first joined the site's predecessor I couldn't for the life of me figure why people were using passive infra red detectors in conjunction with insulation! 

 

"pir" 

[gravelld]

So long as you don't call it SWI I don't mind... (another example of pernicious Government terminology IMO!)

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole

[MarkyP]

loads we could talk about here. I cant give you a cost off hand for my DIY EWI but I recall it was approx 60% of the quotes I was getting which, again from memory, were in the order of £90 - £120 per meter squared all in.

 

reasons I went DIY in addition to cost saving:

 

method statements from suppliers were often behind the times in terms of detailing. for example, I religiously foamed every joint in the EWI boards to ensure thermal continuity, most of suppliers said they didn't do this, one said they filled any gaps with base coat! I used thermally broken fixings which via a special tool are recessed below the EWI surface, these are then capped with a little EPS disc. As well as being better thermally, this also removes the risk of a proud fixing "grinning through" your render. I also used frame seal beads around all the windows, another small detail but one which greatly improves the quality of the reveal render finish and the wind tightness (no need to silicone). I used a PVC starter track, many suppliers quote aluminium which creates a cold bridge should you also go below DPC. So these were all examples of detailing which would have cost me extra or just not been done. Next up, below DPC. Several just weren't prepared to do it, still caught up in trade folklore about the sacred DPC. I think the tide is turning, many system suppliers now have below DPC details, usually called plinth EWI. Most would require the DPC be continuous so break the EWI at the same level. This has been discussed at great length on the other place, and general consensus is that there is no reason to bother breaking at the DPC for reasons of dampness. This means you could just run one pass of EWI from footing to soffit. However, using a starter track does have the benefit of providing a nice level bed for the first course of boards. In my case it also allowed me to break up the work and get the main elevations done. Next year I will install the plinth layer of EPS below the track, slightly recessed, and then go right down to the top of the footings.

 

I fitted the boards myself. It's not too hard once you've done a few, getting the first course plumb and level is key, then it's pretty easy. An 1800mm level and a 2.4m feather edge were hand for checking flatness and plumb. I got whole elevations within a mm or two variation over the 2.4m straight edge, my renderer was very impressed which meant I'd probably gone a bit overboard!

 

I don't much like the texture and finish of the standard thin coat render which most systems use. Avoid, in my opinion, the acrylic and silicone thin coat finishes, go for silicate which is very mineralic and matt and could be painted over in the future with a mineral paint. Another option would be a use a mineral paint over a nicely float finished base coat, that would be lovely I think and very suitable in a period building.

 

I used Baumit render. Very good product and was very happy with the on site and phone tech support. I used their nanopor fine silicate finish which is a very fine grained and very matt, very happy with it. If you are ever over the east side of kent you are welcome to come and have a look and I'll talk you over the whole EWI experience. You can have some fish and chips on the beach afterwards.

 

 

 

 

 

 

[MarkyP]

foamed joints

[MarkyP]

the fixings I mentioned:

 

 

and with EPS cap

 

[MarkyP]

two elevations covered in graphite enhanced EPS

 

[Onoff]

Just now, MarkyP said:

foamed joints

 

What were your base walls like? Mine are VERY rough cast rendered. Did consider sand blasting all the layers of paint off then redering flat before the ewi goes on.

 

 

What did you do ref soil pipes etc?

 

Cheers 

[Onoff]

3 minutes ago, MarkyP said:

two elevations covered in graphite enhanced EPS

 

 

Freaky! I want a slate roof too!

[MarkyP]

sorry for the photo spam, this is the starter track. I'll dig out the concrete path next year and run EPS down to the top of the footings. I  needed to get on with thew main elevations while we had the scaffold. The plinth EWI will be 25mm recessed to form a drip detail, more aesthetic than because a drip is needed. we hacked the existing render off before fitting the track, the  existing render had a very pronounced bellcast bead at the bottom and it kicked out about 30mm. The track allows for a push in bead, you fit the EWI and then a mesh bead slots into the track over the face of the EWI, it means you dont have to worry too much about build up depth. Wemico is the place to look for beads.

 

[MarkyP]

56 minutes ago, Onoff said:

 

What were your base walls like? Mine are VERY rough cast rendered. Did consider sand blasting all the layers of paint off then redering flat before the ewi goes on.

 

 

 

What did you do ref soil pipes etc?

 

Cheers 

my walls were a sand/cement basecoat over blockwork, finished with a pre-coloured spray applied rough cast.The rough cast it turned out was reasonably easy to scrape off, so I paid a lad from the village to do that which revealed the sand and cement underneath which was nice and flat. Subsequent advice was not to have bothered unless the roughcast was blown or loose, which it wasn't. The adhesive makes it easy to set boards flat, you'd be OK over your roughcast. You might want to go over the whole wall with a clip hammer or maybe a scraper to chip through the paint and give a bit more key, I think the adhesive would hold better - but even so the fixings clamp the boards down hard so this might not be necessary.

 

my soil pipe was internal. I guess you could box it with EWI either side, or take it off and re-fit on the surface of the EWI.

[MikeGrahamT21]

Has anyone ever DIY'd rockwool EWI?

 

The older parts of our property which are suitable for this are block and brick cavity (70mm filled with wool), but the mortar is lime based, so I'm keen to keep everything fully breathable, but wondered how easy it was to render rockwool in comparison to EPS? I did EPS on a newer part of the house a few years ago and found it easy to do. I also wonder about Rockwool's ability to cope with some rain on it before it gets rendered, since the elevation to be covered is quite large, it would likely take me a few weeks to complete, perhaps scaffolding with some form of cover on it to protect it from lots of rain?

[Onoff]

3 hours ago, MarkyP said:

my walls were a sand/cement basecoat over blockwork, finished with a pre-coloured spray applied rough cast.The rough cast it turned out was reasonably easy to scrape off, so I paid a lad from the village to do that which revealed the sand and cement underneath which was nice and flat. Subsequent advice was not to have bothered unless the roughcast was blown or loose, which it wasn't. The adhesive makes it easy to set boards flat, you'd be OK over your roughcast. You might want to go over the whole wall with a clip hammer or maybe a scraper to chip through the paint and give a bit more key, I think the adhesive would hold better - but even so the fixings clamp the boards down hard so this might not be necessary.

 

my soil pipe was internal. I guess you could box it with EWI either side, or take it off and re-fit on the surface of the EWI.

 

I could have, should have, would have put the soil pipe inside when I had the chance!

 

The original soil even went under the footings but I capped it off.

 

Idiot boy!

 

 

 

 

[Ed Davies]

6 hours ago, MikeGrahamT21 said:

Has anyone ever DIY'd rockwool EWI?  … but wondered how easy it was to render rockwool in comparison to EPS?

 

A similar approach would be a Larsen truss with mineral-wool infill and some sort of render board on the outside. Not sure if you'd need a ventilated cavity behind the board, though.

[MarkyP]

6 hours ago, MikeGrahamT21 said:

Has anyone ever DIY'd rockwool EWI?

 

The older parts of our property which are suitable for this are block and brick cavity (70mm filled with wool), but the mortar is lime based, so I'm keen to keep everything fully breathable, but wondered how easy it was to render rockwool in comparison to EPS? I did EPS on a newer part of the house a few years ago and found it easy to do. I also wonder about Rockwool's ability to cope with some rain on it before it gets rendered, since the elevation to be covered is quite large, it would likely take me a few weeks to complete, perhaps scaffolding with some form of cover on it to protect it from lots of rain?

 

You can get mineral wool batt and woodfibre board insulation systems with lime renders over, all marketed for situations where a highly vapour open buildup is required. Not sure the reality of the problems they resolve though and at the same time they are more expensive and less insulating than EPS. And EPS is breathable to a good extent (open cell) in any case. Likewise standard cementitious basecoats. 

[MikeGrahamT21]

15 hours ago, Ed Davies said:

 

A similar approach would be a Larsen truss with mineral-wool infill and some sort of render board on the outside. Not sure if you'd need a ventilated cavity behind the board, though.

Yeah I remember a house round here having that done a good 15 years ago, must have been EWI version 1, but I'm guessing the timber will be a massive thermal bridge, so probably not really worth the effort.

 

Yeah the breathability side of things is very debatable, I remember running a WUFI simulation to compare between EPS and Rockwool systems, and the Rockwool system did actually give a condensation risk within its first few years following installation, due to its ability to absorb moisture, something which EPS doesn't really do. EPS is the obvious choice, and indeed the simulations i've run show no risk what so ever, but everywhere you look it says lime anything should remain fully breathable, and i'm not sure EPS would class as that.

[Ed Davies]

38 minutes ago, MikeGrahamT21 said:

but I'm guessing the timber will be a massive thermal bridge, so probably not really worth the effort.

 

Why? They'll only be fairly small gussets of ply going right through so the bridging should be minimal.

[MikeGrahamT21]

On 02/11/2018 at 09:32, Ed Davies said:

 

Why? They'll only be fairly small gussets of ply going right through so the bridging should be minimal.

I was thinking simple timber, this look very similar to those i-joists but with gaps along, so yeah the thermal bridge side of things should be smaller, but still worse than EPS overall, and would be a more expensive system to install since you'd have a requirement for a render carrier wouldn't you?

[Ed Davies]

I looked into doing up an old house a few years ago (while the purchase of my plot was stalled over crofting issues) and quite liked the idea of a Larsen truss for that. Mineral wool is about the cheapest insulation in terms of R-value/£ (just thicker than most other forms) but with the wood, etc, yes, overall it might be a bit more expensive in materials but it'd be a lot more flexible from the point of view of doing bits as the weather permitted, for adapting to oddnesses in the existing walls and for extending the roof over it. Would have timber clad, vertical larch or whatever, if the planners allowed it with a ventilated cavity with woodfibre board behind.

[MikeGrahamT21]

18 hours ago, Ed Davies said:

I looked into doing up an old house a few years ago (while the purchase of my plot was stalled over crofting issues) and quite liked the idea of a Larsen truss for that. Mineral wool is about the cheapest insulation in terms of R-value/£ (just thicker than most other forms) but with the wood, etc, yes, overall it might be a bit more expensive in materials but it'd be a lot more flexible from the point of view of doing bits as the weather permitted, for adapting to oddnesses in the existing walls and for extending the roof over it. Would have timber clad, vertical larch or whatever, if the planners allowed it with a ventilated cavity with woodfibre board behind.

 

Yeah thats potentially the main issue here, i'd have to put planning permission in for anything other than brick finish (we would use resin brick slips like i used on the rear extension), ideally i'd prefer timber or a timber and render combo, I think we'd get it, just a lot of hassle getting there, plus we don't get on with our neighbours which helps greatly lol.

 

What would you do for fire breaks in larsen truss? With EPS you have to have a rockwool section between floors, and though technically we don't have another floor, we do have a large uninhabited loft. Also what is the minimum depth of this system? I was thinking of using 100mm insulation (EPS/Rockwool) in the usual EWI fashion.

 

Next year I plan to renovate the main bedroom, rip up the floor, replace all of our woodwormed timber, and replace, insulate and airtight, and then monitor the heat loss. This room has the largest area of unfilled party wall cavity, which potentially is the main source of heat loss in this room once the floor is done, but there is a chance we may not even require EWI if the heat loss is acceptable. I've been very pleased with the performance of the small bedroom which has had the above done, with no EWI (external wall makeup is approx 0.5U).

[Onoff]

On 01/11/2018 at 11:12, MikeGrahamT21 said:

Has anyone ever DIY'd rockwool EWI?

 

The older parts of our property which are suitable for this are block and brick cavity (70mm filled with wool), but the mortar is lime based, so I'm keen to keep everything fully breathable, but wondered how easy it was to render rockwool in comparison to EPS? I did EPS on a newer part of the house a few years ago and found it easy to do. I also wonder about Rockwool's ability to cope with some rain on it before it gets rendered, since the elevation to be covered is quite large, it would likely take me a few weeks to complete, perhaps scaffolding with some form of cover on it to protect it from lots of rain?

 

Rockwool say here than their slabs specific to EWI have a varying density; a soft inner face to take up irregularities in the wall face and a harder outer to render onto...apparently!

 

https://cdn01.rockwool.co.uk/siteassets/rw-uk/literature-downloads/datasheets/ewi-slab.pdf?f=20180917035840

 

I like the fact they're Euroclass A1 - non combustible.

[gravelld]

Personally I feel the LT approach is superior to sticky block. Quite a few examples of it in this country but it's generally more popular abroad, especially the States. There was a company in Germany (Lignotrend?) who were making factory built LTs.

 

UK examples I know of: Charlie Luxton's (using I beams in a new build) the Simmonds-Mills retrofit. A well known TF supplier has a solution too which somehow they appear to have got a patent for, but I probably misunderstand why they were granted that. They use EPS rather than mineral wool.