Posted By: Nick ParsonsFostertom wrote:

''EPS-and-render EWI systems are water-vapour breatheable, as well as providing a liquid-water protective layer. But non-EPS plastic insulations are not breatheable.''

But surely the acrylic 'fat paint' renders are not breathable?

According to Alsecco printed comics:
"Vapour permeable: Alsecco renders are designed to allow the building to breathe ...
... the mineral renders are particularly open to diffusion ... silicate renders have high CO2 and water vapour permeability ... silicone render top marks in ... water vapour permeability ... synthetic-resin renders ... are still water vapour permeable ..."

Posted By: SaintNor is EPS in reality according to Springvale, EPS manufacturers

Data seems to vary considerably between manufacturers, and the generic figures are in the middle. Even at best, EPS is not near-transparent, like breather felt; at worst, it is still on the low-resistance end of the scale, unlike other plastic insulations.

It's worth considering that EPS has the longest track record for EWI. The Sussex-based EWI company which I'm using (and for whom EWI is 90% of their business), have said that their render supplier has had a higher failure rate with phenolic boards, and as a result they're not recommending the use of phenolic boards at the moment.

It's also worth noting that once you take the foil coatings off PIR or phenolic boards, then they lose their Pentane more quickly, so you're looking at a k value of around 0.026 W/m·K or so after a few years:

http://www.parsiblog.com/PhotoAlbum/pursandwich/data001.jpg

Graphite enhanced EPS comes in at 0.030 W/m·K so EPS isn't as pants as it first looks, and in the end, that's what I decided to go for.

BTW, non-foil faced PIR is reaonsably breathable (the alu foil facings aren't obviously!).

I've been going to a local independent insulation supplier for my EPS and PIR, they use various suppliers, but most of their EPS comes from Kay-Metzeler...

Tim.

Posted By: TimSmallIt's also worth noting that once you take the foil coatings off PIR or phenolic boards, then they lose their Pentane more quickly, so you're looking at a k value of around 0.026 W/m·K or so after a few years:

Tim, yes I always use 0.0245 for PIR..pernickety I know and 0.027 for PUR. I get both of them sliced from bunstock so they are unfaced. As for phenolic......

1/2 as much as EPS ( PUR/PIR without foil Vapour Permeability 300 r )

12 x less than wood fibre or cellulose
http://www.natural-building.co.uk/PDF/Breathability-Matters-response-to-Kingspan.pdf

Posted By: jamesingram1/2 as much as EPS
http://www.natural-building.co.uk/PDF/Breathability-Matters-response-to-Kingspan.pdf

That's Neil May, but talking about XPS not EPS in the table in that document.

AFAIK only EPS is 'moderately breatheable' - all the other plastic insulations incl XPS aren't.
The fuller version of that table, by same author (sorry don't have the link to hand) gives resistivities:

EPS resistivity 100-750MNs/gm, gives diffusion resistance factor mu (as quoted by ASHRAE) = 20-150 (divide by 5)
XPS 600-1500, gives mu = 120-300
PU foam 115-1000, gives mu = 23-200
OSB 100-300, gives mu = 20-60
Blown cellulose 40-50, gives mu = 8-10
Spruce 45-1850 ("most solid timber is around 200"), gives mu = 9-370
Oak, ash, beech 200-1850, gives mu = 40-370
Plasterboard 40-70, gives mu = 8-14
Air 5, gives mu = 1

So Neil has considerable differences with ASHRAE's academic extreme ranges - I prefer to believe that Neil gives the workable range.

According to me (what I work to) from inside to out:
Plasterboard 50MNs/gm
Blown cellulose 50
OSB 300 (9 thick)
EPS 150 (at least 1.5 x as thick as the cellulose)
breather felt ?10?
which goes in the right direction as, but is quite far from, the 5:1 inside:outside resistivity (or is it resistance?) rule of thumb - but seems to work safely in the Euler-based interstitial condensation calculators. How it would fare in full WUFI I'd love to know.

Sure, but it rarely works - conversations tend to continue where they started despite 'please continue this at ....' efforts to establish an alternative, and then you get two conversations that aren't 'seeing' the other. Anyway, I didn't start it!

I have heard this as well, albeit only on here and AECB. If so, why is it still being manufactured and installed by the masses? Its not like this is job number 10 of insulating a house in the UK, my house will be job number what 400'000?

If i go for the fully installed £65/m2 quote from wetherby I will get the 10 year guarantee as well. I can also request that they supply the boards and store them outside for 3 months at my house to prevent shrinkage. I believe that it Wetherby were revisiting every job they had done because of shrinkage then they wouldnt be fitting the stuff. Perhaps we are seeing a mistake by the manufacturers of a manufacturing defect in certain batch runs, or maybe some batches are not stored for long enough to allow for proper shrinkage.

Yes, £65 for 100mm phenolic, when some years ago I paid nearly £140 for 50mm seems quite good!!! I share the concerns re phenolic, though, and have just avoided using it on an IWI job because of those concerns. I hope that in time all EWI (and IWI) installers will offer thermograhic pics in the first cold weather after installation, and 5 and 10 years on, as part of the guarantee.

Maybe I'm putting an optimistic spin on it.

This quote was asuming:
Walls are prepared back to block/brick.
Guttering does not need to be removed (i will have to do it since we have concrete gutters its a specialist job to remove and replace with plastic), I will install 100mm insulation beneath the fascia boarding for the EWi to butt up against.
All accesories, gates, pipes etc will be removed or extended.
I am replacing the windows just befor the render job, so the cills will be the exact size and the windows themselves will be flush with the wall and surrounded by a layer of insulation to make EWI install easy and cold bridge free.

It also does not include scaffolding which i will need to strip the walls in the first place.

So there are other costs involved, but they are all minor or more to do with the general upgrade of other aspects of the house like the windows and the horrible concrete gutters.

Posted By: eniacsI have heard this as well, albeit only on here and AECB. If so, why is it still being manufactured and installed by the masses? Its not like this is job number 10 of insulating a house in the UK, my house will be job number what 400'000?

For phenolic? 400k sounds like it might be 1 or 2 orders of magnitude high... I don't have direct experience of this, only going by what my rendering firm said - the guy in question does seem pretty knowledgeable, and uses multiple suppliers / systems (mainly Weber at the moment).

If i go for the fully installed £65/m2 quote from wetherby I will get the 10 year guarantee as well. I can also request that they supply the boards and store them outside for 3 months at my house to prevent shrinkage.

Sounds like a reasonable precaution - esp if this is done over the summer. I've also be told (by the same bloke) that the surface of phenolic goes powdery when exposed to UV light, so you'll want to shade it if you go for this option. As you said, it might well be down to a manufacturing defect / bad batch etc. and if someone's going to guarantee it for 10 years, then it sounds good.

For comparison, I was quoted "£75 to £80" per m² for 125mm graphite EPS with an Acrylic render, in Brighton a few months ago, or "£45 to £50" per m² for render application only (dual coat system). A problem with sourcing the materials yourself, is that you end up paying 20% VAT, whereas the installers can charge 5%...

Tim.

I thought i read somewhere that 1.2million home sin the uk were EWI'd so i asumed about 1/3 of them would be with kingspans K5 since it seems to be stocked by every local supplier in the standard sizes.

I can't imagine there is so many EWI installations in the UK already, I reckon it's about 10% of that figure on a good day.

Your £65m2 quote sounds good , and as Tim mentioned the precaution you suggest make sense .
The area of work you discribe as minor and to do with your general upgrade , ie enabling works can be quite involved and labour intensive so your making a good saving doing this yourself
. Scaffold cost approx £16+vat linear m per lift.
2 coat render systems usually require 3 trip to the wall for plasterer plus priming coat and mesh , trims and beads .