As usual, manufacturer's websites puff the wonders of their products. On this forum I find talk of cost, extending roofs and internal vs external.

But what I'd really like to know is, How will external insulation go wrong?

How might the installers stuff up in the first place?
What probs happen after insulation? Mould - where? Render cracking off? How does it respond to impact?
External insulation is described as lasting 25-30 years - how does it fail? What do you do then?

Is there anywhere I can see some that's been up for 20 years?

If we fit it, we'll have through-colour render due to difficulty of painting side of house (narrow alley) - what does that look like after 10 years?

All wisdom most gratefully received!

I did two or three lots some 30 years ago -- still up -- few minor cracks and the haven't even repainted it!

In Germany it is extreemly common. Some concrete panel tower blocks have it in the UK.

Almost no down side -- Not good with impact but how often do we hit housed with things?, surface green algae in damp shaded parts --not a problem, If you are Thames Valley have a look at my ones - whisper for addresses. Installers can mess up round scaffold put-locks/lift height joins. They can also be none too clever thinkers when it comes to pipes and wires so do your own thinking and altering before they come.

Very interesting paper, Peter. In particular, suggests less cracking of render can be expected, due to decoupling of render from masonry.

Tony, your experience is also v encouraging. Don't think I can make to Thames Valley awhile - maybe in a few years!

Brian, yes, I'd read about drainable cladding systems, which made me wonder how water got behind the cladding in the first place, assuming the roof was extended. Are we talking poor worksmanship yet again?

External breathability isn't on the cards, unless we hack off the Victorian render and 130 years' accretion of every type of paint plus a semi-failed spray render (scraped off where loose during last paint job). We'll probably go for waterproof outside, vapour-permeable (or completely breathable) inside, since interior plaster may need to come off AGAIN anyway Frankly, the render may be holding that wall up...

Posted By: JackyRWe'll probably go for waterproof outside, vapour-permeable (or completely breathable) inside

Or maybe not. Ball-park quote for 80m2-ish end of terrace: 12K. Pounds. Sterling.

Think that was PIR, but my brain was leaking out of my ears by then...

[edited] Yes, Rumi also very kindly gave me a ball-park quote - with an excellent breakdown. Will ask his (her?) permish to discuss (not tonight). But s/he's been very helpful - and it's definitely waaay too expensive for us.

I'm not a payback fiend, but £12K cladding when the house only cost £120K?

Life's too short to mess about with all that stuff...working external insulation around pipes and bay windows...not to mention the eaves, and Tony's recommendation that, of course it has to go below ground...jeez

We are in a short term world...try this (no I have not used it and know nothing about the company) you will never get your money back from messing about with expensive technologies...just stay comfortable, and keep the bills as low as possible...phew

http://www.mgcltd.co.uk/Products/Thermal_and_Acoustic_Insulation/SEMPATAP_THERMAL/

Sempatap is much worse than celotex for internal insualtion. It's sole advantage is that you can put it up relatively quickly and easily like wallpaper. But it is expensive and the insulation value is not very high (not least because it's only 10mm thick). I think it is of similar insulating value to rockwool, but not quite as good (don't have numbers to hand) - i.e about half as good as PUR (of the same thickness).

You'd be much better off spending slightly less money on 50mm celotex and separate plasterboard, or for about 25% more bonded PUR/foil/plasterboard (e.g. Kingspan K17). Obviously if you really can't lose 60mm of space then the more expensive PIR boards (K18) are a bit thinner or you can just choose thinner size. even 20mm PIR/PUR will be about 4 times as good as a layer of sempatap.

Putting up the boards yourself is easy enough. Bit tedious fitting round windows etc but not hard. I've done it before with foam-backed wallboards, and am just about to do it with plain celotex+plasterboard. I looked at Sempatap whilst checking out options.

Hello

Rumi here Im male by the way, not that it should matter.

With EWI the devil is in the detail. Buildings, mainly dwellings, are a very in my experience, unless meticulously built, a mix of very poorly fitted relatively products which are relatively incompatible. Most of th buildings I have added insulation to the outsde of had poorly fitted windows and doors which generally ere very drafty, along with poorly sealed gas flues, extractors and other throught tha wall systems. All were being rerendered and had between 50-100mm of polyeurothane and render added to their exterior.

I am very aware that costs are a big issue, and towards trying to reduce costs we ave been starting to move towards providing altenative cladding systems including prefabricated rendered panels.

I think the best way to keep the costs under controll is not to render the whole building. The cost of applying the insulation is low for use with a cladding system. For applying render there needs to be a high number of fixings, 18/sqm the mesh has to be stainless as do the profiles.

Getting your local builder to work to a technical spec might be possible, but I think there would be the added cost and necessity of employing an architect to supervise the installation.

As I said before the devil is in the detail:
1. Windows, doors, roofs, vents, flues, cable entries, draisn and DPC.

2, Insulation Materials, Natural, bidegradeble, Breathable, CO2 Nuetral or not

3, Render, Lime or Lime polymer fibre or sand/cement with lime added for flexibility.

4, Cladding Systems - high or low tech?

And finally thickness, 75-100mmis more cost effective than 25-50mm. because the difeerence between the 2 is 200-500 quid.

Rumi,

Thanks for the detailed cost breakdown, bearing in mind it is just an example.

Posted By: rumi_ecobuilderI think the best way to keep the costs under control is not to render the whole building. The cost of applying the insulation is low for use with a cladding system.

Interesting, what effect would cladding instead of rendering have on your cost breakdown?

Peter

Hi Tony,

It does not have to pay back, but spending 12K on doing it will be easier if there is a personal benefit as well as an environmental one. Therefore more people will choose to do it.

Is there a personal financial benefit that mitigates against the high initial cost, if so how much do you think?

Peter

But there is a payback from EWI, I just don't know at all what it might be, and I am interested to know.

Conservatories and garages have other obvious benefits, and so we can ignore the payback. But what is the other obvious benefit, to me, of paying for EWI?

Peter

Seems to me that the "sole advantage" mentioned by Wookey is a big plus. The stuff can be applied on any wall without messing around with moving skirtings and facings etc...though I have no idea how you hang pictures!
It must be cheaper than Celotex internal bacause of reduced labour, and fiddling around openings etc...and way cheaper than external (how do you deal with bay windows, service pipes, eaves and ground level, window ingoes in a typical terraced house?) OK I agree if you have the whole row to refurb from scratch, but that's a serious grant job (if you get everyone to agree), and it may be cheaper to flatten the lot anyway...payback must come into it...people buy cars, sofas, TVs, HiFis etc etc without considering payback because they throw them away and seem to be happy to do so...rightly or wrongly.
Everyone is looking for a quick, cheap comfort fix (viz plastic double glazing...instant comfort...OK looks crap, not cheap, but still selling), so once Sempa gets going it'll be a winner, regardless what we think or say. I'm a fan of MHVR and tight draught stripping but that's not going to win any friends...the government doesn't even know that exists

Also what would happen to Sempa if it burnt?

If it is an isicyanate (Urethane/polyurethane) then these can release VERY toxic gases; Although I will not comment on this specific product.

The last time I looked at an polyurethane interior wall lining it had to have a plaster skim coat for fire protection.

If you are going to that trouble you may as well do it properly and dry-line (In my view), (or using insulating paint that is inert) - two ends of the spectrum.

Yo, this is getting confusing - especially, if you'll excuse me Caliwag, leaping back to a different material and referring to it only as "the stuff"!!!

New thread for Sempatap discussion?

Posted By: JackyRNew thread for Sempatap discussion?

Please God no.....