EWI insulation shrinkage

[Nigel Murray]

At yesterdays local group meeting – SW Cornwall – there was some discussion about EWI systems.
There were some recommendations for the best options for insulation however there was also some experience of Phenolic or PIR/PUR boards shrinking over time.
Has anyone else had experience of this?
Anyone got any published reports or manufacturers statistics showing how to deal with this? or rates of shrinkage? etc.

The Denby Dale passivehaus used the expanding foam method to 'seal' the irregular gaps. Does anyone think this method would bind the boards together and resist any shrinkage?

Nigel

[Nigel Murray]

Unfortunatelly I cant get the Search function to work.. saw the post thanks Kate… but while looking elsewhere i found this thread

I am doing the same research. We recently visited Adam Dadeby's PH refurb in Totnes, where he is using phenolic insulation to keep the thickness down. A stack of boards seemed to show degradation from the sun, and I have heard warnings about phenolic delaminating. I am looking at EPS with graphite, which seems to give a good price to performance ratio. It has the additional feature of being vapour permeable, unlike the extruded products.

Any further info Rob ? or Adam?

regards
Nigel

[Nigel Murray]

And to top off this non-discussion the chosen rep for the job I'm involbved in just called to say that they had had trouble with phenolic and they wanted to steer me away from using it – recommending graphite EPS instead… and for less cost
Now just have to persuade the owner…

Nigel

[Anonymous]

I am going to stick my oar in here. EPS is the most stable of the sheet insulation mentioned but I worry about the Neopor due to lack of data with regards to renders adhering to. Depending on density the advantage over Styropor varies but the worry for me is, as graphite is used as a lubricant, to expect render to stay stuck to it over time is the question I feel needs answering.

[Nigel Murray]

Thanks for the input.

… but I worry about the Neopor due to lack of data with regards to renders adhering to. … the worry for me is, as graphite is used as a lubricant, to expect render to stay stuck to it over time is the question I feel needs answering.

Good point, but is the surface not textured in any way?
I would assume the surface is hardly smooth with all the gaps between the beads. Dont you think this will provide enough keying?

Nigel

[Anonymous]

Any good installer of thin coat renders will/should rasp the wall first to create a good “key” before applying the base coat and imbedding the mesh.

[Nigel Murray]

Any readers seen the ceiling of the Ikea Dublin carpark? Reported as having shrunken boards and delaminating foil???

[Mark Siddall]

If you have seen the above you could post photos here.

[Anonymous]

Nigel,
Been meaning to reply for a while but haven't been able to track down the article I promised. There is growing concern within the industry about phenolic shrinkage – a phenomenon acknowledged in this article here http://www.ehow.com/info_8315624_risks-phenolic-foam-insulation.html. I have seen pictures of a recent installation in Plymouth where the shrinkage in an EWI situation was pronounced and visible as horizontal lines. When the boards were cut out, large gaps were apparent and the boards had bowed when compared to a new board. Phenolic is also vulnerable to moisture within the existing structure trying to migrate out of the original construction. EPS doesnt have these risks but still requires great skill in ensuring there are no angular gaps at junctions. It also has twice the embodied energy of stone wool or wood fibre alternatives and none of the acoustic and fireproof qualities.

[Mike Whitfield]

There is a very good article in the American magazine 'Fine Homebuilding', issue no. 225, March 2012, page 55. A builder in Massachussets who did a 'deep-energy retrofit' on his house and office/ barn conversion sixteen years ago decided to update the barn conversion. He stripped it down again and analysed the performance of the various components. He had wrapped the barn in a single layer of EPS taped and mastic-ed at the joints. The boards shrunk, the tape /mastic cracked, and the joints opened. He could see this starting in the first winter with frost melting on the joint lines. He had used a single layer of XPS sealed with Tyvek tape on parts of his main house, so he removed the weatherboards and investigated that, and found that the joints and tape were in perfect condition after 16 yrs.

[Anonymous]

My understanding was that foam insulation does most it's shrinking just after manifacture , so board used for
EWI should be aged ( allowed to shrink ) prior to installation . Might it be the case that this was not done correctly in some instance?

[Mark Siddall]

A few years ago at an AECB Conference Berthold Kaufmann from the Passivhaus Institute noted that EPS can shrink by about 10-20mm per meter within the first 30-60 days. Like John he suggests a maturation period before installing on site. Unfortunately manufacturers do not make this allowance when supplying theior materials to industry….

Mark

[Anonymous]

Mark, not all suppliers do that. We have all of our products go in a curing oven for 48 hours after coming out of the moulds, for precisely the reason being discussed.

[Anonymous]

Yes, a supplier I use for graphite EPS advises 'ageing for shrinkage' of boards for EWI use also and usually does this at the production plant. I was wondering if perhaps on the larger jobs , where product was manifactured specificially for a project, this may be missed ? or is it the case that phenolic needs a longer time to allow for intial shrinkage?

[Nigel Murray]

Yes, a supplier I use for graphite EPS advises 'ageing for shrinkage' of boards for EWI use also and usually does this at the production plant. I was wondering if perhaps on the larger jobs , where product was manifactured specificially for a project, this may be missed ? or is it the case that phenolic needs a longer time to allow for intial shrinkage?

Thanks J, and when I phoned Kay-Metzeler, they said 'most customers ask for it to be 'aged' 2-3 weeks in block form i.e. before cutting to sheet thickness. Have you seen any further shrinkage on jobs using this product?
Nigel

[Anonymous]

Not once rendered , but then it would be hard to tell.
I left some EPS installed on the wall, unrendered on one job for a couple of months, the boards exposed to the sun shrunk (after aged prior to installation ) approx 5mm , though in shade didn't. Whether this would happen underneath when covered by render I'm unsure.

[Anonymous]

posted here re. phenolic
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=9202&page=1#Comment_148688
“BTW, the rendering company which I'm using was warning me off Phenolic due to the realively high failure rates which they'd been hearing about from their EWI supplier's rep.”

[Tom Foster]

Any further comments on this?

The various proprietary suppliers of EWI systems do charge a lot for their non-standard-size (e.g. 500×1000) insulation boards, which I think are invariably 'aged'. It's tempting to buy 8x4s of standard insulation and cut it up, but I for one think there's good reasons to pay up for the proprietary suppliers' boards, certainly when it's going to be rendered. We don't want to see 'giant brick' effect after a couple of years or less, esp knowing the shrinkage gaps that will lie behind.

But what about EWI that's going to be clad e.g. with boarding. Not sure that's really called EWI? I have found myself treating it differently, as ordinary builders work, using those 8x4s of insulation board – seamless with same on the roof slopes. Of course no one ever sees the telltale 'giant brick' effect but I guess the shrinkage gaps are there. Or are they? We glue the boards with roofing contact adhesive to continuous OSB, and we foam all the joints however tight they are. or we do both of those in one go if using foaming polyurethane glue.

In this latter non-rendered case, should be be using aged insulation boards? If not, if we're doing enough to ensure no shrinkage gaps, then why must the boards be aged when rendered?

[Anonymous]

Hi all,

I'd be grateful to learn if rigid insulation boards of various types are still considered at risk of shrinkage, and whether leaving them to age on site for a few weeks is sufficient. I'm currently deciding whether to use EWI or mineral fibre filled wall/larson trusses for a Passivhaus.

Cheers

[Anonymous]

Thanks for that Nigel.

I'm fairly sure I once did the calculations and found that the energy saving was much greater than the embodied energy over the lifetime of a building. However, I never regarded this as particularly useful if I could make the same savings using an insulation with lower embodied energy. I tend to use the best insulation for the job, which could result in a wide range of materials in one project. Not everybody wants 2' walls!

I personally hope that PH doesn't change to take embodied energy into consideration. I think it would kill the standard if every item used in the building, and presumably all of the energy of the building process, had to be recorded. It brings back memories of last year's Code 6 build on Grand Designs. Mountains of paperwork.

[Tom Foster]

Yes AFAIK all the artificial insulations pay for themselves multi multi times over. Insulation is the best possible use of oil/hydrocarbons, if you must. What was that podcast?

… to take embodied energy into consideration. I think it would kill the standard if every item used in the building, and presumably all of the energy of the building process, had to be recorded

It surely should be an essential part of the building process in general – though we and the world are still practically a long way from taking that on board – otherwise we're knowingly omitting about half the point.

Paperwork – well that's something that's potential with BIM – on-the-fly embodied energy (in fact whole LCA) totalling as the design/documentation progresses – though again, the BIM cos haven't go round to incorporating that data/facility yet. Strangely, mech eng/product design software is much further aheads on just this, than building's, even though sustainability awareness is much higher in building than in engineering.

[Author]

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