Green Building Forum - External insulation - any pitfalls?

External insulation - any pitfalls?

JackyR — Mon, 12 Jan 2009 18:29:30 +0000

Posted By: James Norton
Well just the same as a conservatory really...

Your house looks nicer
Its a nicer internal environment

Eh?
a) Conservatory has additional functions.
b) You're joking, right?
c) Possibly if you have mould, but for many people the energy used to achieve the same level of comfort will be the only difference.

But also you get the added value from...

Lower fuel bills*
Reduced C02 footprint

These may add sales value - but only if buyer prepared to pay extra for the lower fuel bills.

I'm not motivated primarily by payback, but am finding EWI hard to justify.
1) Regardless of how you hope to finance it (borrowing, recouping when sell), the purely financial payback in cost of fuel saved seems 20-40 years (at very approx current prices). OK, but:
2) Installers describe lifetimes for their systems of 25-30 years.
3) We've been complaining about new builds with life expectancies of 25-30 years.
4) An old build like mine has so many problems I wouldn't like to predict its life expectancy. (Love my house dearly, but it's built like c**p. Or possibly of c**p.)
5) What's the LCA for EWI? I can't imagine it's carbon neutral to make/install.
6) [edited] Maybe I should just seal all the drafts, turn the heating down and spend the money on aerogel for my floors...

[NB figures from my own circumstances and memory. Knauf calculator and general case might get different figures]

I've argued myself into a corner, as I firmly believe the existing stock needs dealt with - but I can't imagine how. My own place has futher probs: can't insulate the front externally, as conservation area; and bricks are breaking down, so daren't insulate internally in case this accelerates.

External insulation - any pitfalls?

jamesingram — Mon, 12 Jan 2009 18:45:31 +0000

i bet Tony didn't charge Â£150m2 (or the equivilent 20 years ago) , how about looking for some more quotes , EWI doesn't have to be that expensive

External insulation - any pitfalls?

caliwag — Mon, 12 Jan 2009 19:15:30 +0000

I welcome a new thread on Sempa and all internal insulation methods...but if we are saying that all internal systems create the opportunity of mould at some point behind the insulation, then we truely are doomed. I believe that old terraces etc should be (government funded) seriously draught stripped and have MHVR installed. Until that happens, for comfort for the vast majority of these places, we should be considering a reasonable, thin internal insulation, and Sempa seems to do that.
At 10mm you can just stop it at skirtings, facings and leave a shadow gap...OK there's an edge detail issue...easily dealt with to my mind...and not beyond the wit of detailers.
It seems to me to be a complete waste of time pushing external insulation, particularly in terraces, (how many are there inthe UK?) when it just isn't going to happen...comfort and lower bills are vital. We do the public a dis-service pushing otherwise.
Anyway all this has to go hand-in-hand with a public education programme about the origins of condensation, damp and mould. You only need to visit other building forums to realise that there is a lot of ignorance out there...sorry!

External insulation - any pitfalls?

jamesingram — Mon, 12 Jan 2009 19:23:38 +0000

"It seems to me to be a complete waste of time pushing external insulation, particularly in terraces,"
sorry, I'd have to disagree

I worked on a row of 1950s terraced houses that were externally insulated 10+ years ago (won some award I believe), rockwool and pebble dash , still look good and residence very happy with there lower heating bills
the way to do them is as a job lot

(edit for my rubbish grammer/spelling, as usual)

External insulation - any pitfalls?

James Norton — Mon, 12 Jan 2009 21:44:20 +0000

Ok Jacky, I probably am being a little flippant, but the idea was to illustrate the non financial payback problem :- essentially many people (not necessarily your good self) are happy to spent thousands on so called home improvements with only 2 criteria.

1- Does it make my houses a better place to live in (functionally, aesthetically or emotionally)
2 - Will that be at all positively reflected in the sale price

energy saving improvements score on both those as to how much then that's somewhat in the eye of the beholder

Life span of systems
Guarantees give 25 years based on what an insurance company will back up - no reason why a render finish will not last well in excess of that before serious maintenance and if maintained over the years indefinitely.

EWI really stacks up if you are having to do work to the outside anyway - try getting quotes for knocking off existing render and re applying or repointing and sandblasting etc - as many people do and happily pay many thousands of pounds because of the same reasons as above. The same is true for internal wall insulation - ie many people pay thousands to have the walls re plastered and new skirtings put on for those same reasons without a thought to adding some insulation.

The only bit we should be thinking about asking to pay back is the extra over for the actual insulation and its fitting.

If you're not in the market for new plastered walls or a new facade, or have a spare Â£10k just lying around then maybe another tack is in order for an old house made like and of c**p, for eg:

1. loft insulation
2. obsess over air leaks and pipe lagging
3. replace boiler if due if not then replace single glazing (or vice versa)
4. DIY Night shutters to windows or IWI to wall with least exposure to sun or EWI to one that most needs attention already
5. Solar hot water if simple with heating system and roof
6. Rest of insulation / rest of windows

J

(PS IWI is not as bad as all that neither is mixing the two just easier to do wrong and not good for the really top notch levels of performance - see fundamentals section or EST best practice)

(PPS
Terraces are ideal for EWI as long as you do the whole road or as long as many of the houses aren't left empty for weeks on end.)

External insulation - any pitfalls?

Peter Clark — Tue, 13 Jan 2009 11:14:49 +0000

This web site of an Irish builder gives some prices (about 100 Euros per M2) and justification of EWI:

http://www.viking-house.ie/external-insulation-and-cladding

Any thoughts anyone?

Peter

External insulation - any pitfalls?

djh — Tue, 13 Jan 2009 14:19:59 +0000

I'm getting confused about the costs. I saw an initial figure of 80 m2, which I took to be a floor area, and a cost of Â£12,000. The house is a semi so has three external walls, each a bit less than 9 m if the house is square. Guess at a wall height of 5 m gives me a wall area of about 130 m2 so cost /m2 of < Â£100 Rumi's figures seemed to be in the same ballpark.

Where do numbers like Â£150 /m2 come from?

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 14:31:51 +0000

Hm.

With external wall insulation, space-heating for 2000 sq ft cottage cost â‚¬350 for the year.

Without insulation, my gas bill (inc DHW but not cooking) was less than Â£300 = â‚¬333 last year. My house is less than 800 sq ft.

We should have a lower figure next year due to solar, TRVs, condensing boiler, loft top-up and draftstripping. Of course, we don't know about number of occupants, heating pattern etc, and comparing money not kWh or Joules is dodgy.

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 14:33:58 +0000

[deleted]

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 14:47:23 +0000

OK, djh you're right, 80m² must be floor area and I've been at cross purposes with suppliers. That would explain why their typical semi is 80m² while I was getting about 100m² not including front...

But as the costs aren't linear, I'm not sure how much difference it makes to the ball-park figs we've been using.

[edited for typo]

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 14:56:01 +0000

Checking my files, one ball-park quote explicitly stated Â£130 / m² for my house. He further stated this was assuming a job of 90 to 100 m² wall area, and that larger jobs usually cost less per m².

External insulation - any pitfalls?

Peter Clark — Tue, 13 Jan 2009 15:21:55 +0000

I may have contributed to the confusion by assuming 80 m2 was wall and not floor,

The costs issue is a bit clearer to me now, thanks for this discussion everyone.

Any thoughts on the EWI justification in that link above?

â€˜the only safe option is to leave a ventilated cavity between the drylining and the wall or put the insulation on the outsideâ€™

Peter

External insulation - any pitfalls?

Matt — Tue, 13 Jan 2009 15:37:18 +0000

James - GWP for Pavatex is -99 - but LCA does have carbon (released at end of life through decomposition), having said that you are locking it up for life of the product on the build, and if you then chuck it in the incinerator for heat/power, you are maximising its use...

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 16:22:12 +0000

Plus expanded steel mesh plus Portland-cement-mix render (unless rendering already). Plus transport to site for all above.

External insulation - any pitfalls?

jamesingram — Tue, 13 Jan 2009 16:28:16 +0000

Rendering and such like is usually quoted for wall area m2 , most buildrs would include windows etc as this will cover the cost of detailing around them
average semi external wall areas about 80-110m2
I was presuming this so 12,000/80=150m2

say for 100m2 of wall (5/10/5 linear m, 5m high)
materials estimates
scaffolding Â£16 linear m , per lift , say 3 lifts max =Â£10m2
insulation (100mm PUR)and fixings Â£15 m2
mesh, fixings Â£15m2, fancy stuff with paper backing
2 coat render labour and material about Â£25 m2 , perhaps a bit high
paint render say Â£ 6m2 ,unless you go for through colour render, then increase render cost may pay off against painting
that Â£56 m2,
you just got to think about fixing the insulation and mesh say Â£15m2 to give you time on detailing, (Â£1500 so 10 days at Â£150)
add 15% profit , and you end up around Â£82m2
then stick some vat on it and hay presto Â£ 95m2
100m2 = Â£9500
thats SE UK prices so I'm sure you could get it cheaper

this would make a solid wall approx u value = 0.22 W/m2K

cheers Jim

(edit as I change the insulation fixing cost as I thought it was to high)

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 17:15:07 +0000

Yeah, I think insulation-fixing cost is easily underestimated. Rumi's ball-park quote allows 2 men x 8 days.

We (well, certainly I) whinge plenty about minor careless workmanship negating whole jobs. Both EWI folk I've spoken to (one a product supplier not installer) have emphasised that there horned red gentleman resides in the detail.

External insulation - any pitfalls?

jamesingram — Tue, 13 Jan 2009 17:19:52 +0000

so , just to be clear , do you know what the wall m2 is for the Rumi's estimate ? as I'm still a bit confused

I'm interested in getting a good realisitic estimate for EWI per m2 fitted by local tradesmen as I believe its the way to go , and showing it clearly here
might encourage people to go for it, whilst showing up any excessive profiteering in this area .

removing the builder and profit/vat that unfortunately they have to charge and going straight to the plasterer/render, using EPS insulation, expamet mesh and mortar dye as colouring could get this 95m2 price down quite a bit , say to 50-70m2,
though if soil pipes and stacks, verges , tiling, sils all need adjustment then I could see it spiralling upwards

I did XPS insulation /GRP render / weathertex coating( nasty stuff ) of prefab tin-tops in the early 90s as a labourer and it was about 20 man days all in
for a large semi , though at the time insulation detailing wasn't top of our list, getting it done quickly was .

External insulation - any pitfalls?

JackyR — Tue, 13 Jan 2009 17:30:50 +0000

"The quotations below are based on the dimension of 80 sqm supplied by you and subject to survey "
Rumi, wanna expound?

External insulation - any pitfalls?

jamesingram — Tue, 13 Jan 2009 21:52:57 +0000

Peter , interesting site , lots to read
edited as my question was nonsense

External insulation - any pitfalls?

dazdread — Wed, 14 Jan 2009 14:11:53 +0000

Hi Peter...

I have done a quick search and see no mention of this DIY External insulation course... any ideas?

Where was this row of 1950's terrace houses that had been insulated?

Darren

External insulation - any pitfalls?

Peter Clark — Wed, 14 Jan 2009 14:26:40 +0000

Posted By: dazdreadI have done a quick search and see no mention of this DIY External insulation course... any ideas?

Where was this row of 1950's terrace houses that had been insulated?

Hi Daz,

In this thread SimonH mentioned some courses:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3254&page=1#Item_12

terraces was someone else.

Peter

External insulation - any pitfalls?

dazdread — Wed, 14 Jan 2009 17:08:03 +0000

Many thanks, will have a good gander

External insulation - any pitfalls?

chrisc — Wed, 14 Jan 2009 20:55:49 +0000

How does external insulation and a new leaf of brickwork compare cost wise to insulation and render I wonder -- does cheaper insulation off set the extra labour and material costs of brickwork? Is there that much in it?

Of course details around windows and eves would probably be even trickier...

External insulation - any pitfalls?

jamesingram — Wed, 14 Jan 2009 21:14:10 +0000

I would have thought your suggestion would be more expensive
Though I've seen it being down on a gable end once ( no windows , just extra work on a new gable ladder and barge board,verges )
I presume it was to keep the estheics of a brick finish
what about the footing, wall ties for wind bracing , lintels , cavity tray etc. lots of problem to over come

Jim

External insulation - any pitfalls?

fostertom — Wed, 28 Jan 2009 22:27:45 +0000

More about the economics -
What's the insul thickness break-point at which it becomes much more expensive to fix? 100? I'd guess that, apart from cost of the boards, EWI costs same for anything up to 100, but rapidly costs more to go beyond that, to 150 or whatever? So using 100 Cellotex might cost same or less as using 150 EPS, for similar U-value?
And about good practice -
I can hardly believe that all systems put the render more or less straight on the insulation, without a ventilated air gap. How can that possibly allow outward vapour to disperse?
What about using pukka Rendalath - unnecessarily expensive?

External insulation - any pitfalls?

jamesingram — Sat, 07 Feb 2009 16:17:11 +0000

http://www.wbs-ltd.co.uk/images/pdfs/literature/WBS_EWI_Refurbishment.pdf

some installation details here
http://www.wbs-ltd.co.uk/images/pdfs/literature/WBS_EWI_Refurbishment.pdf
for general info.

http://www.brc-special-products.co.uk/downloads/Rendalath%20Specifiers%20Guide.pdf?CFID=368873&CFTOKEN=41115302
hi tom
I was considering using renderlath on Pur board as two seperate items, presuming the paper would allow/create the air gap suggested, looking at these details they offer laminated panel , showing no space as you mention , this concerns me slighty, how important is this airspace/drain

cheers Jim

External insulation - any pitfalls?

Arnold — Mon, 23 Mar 2009 13:03:07 +0000

Brick Slips,

I've been talking to manufacturer of brick slips to see if its possible to get ones that will match my 1890's Terrace.

he seems to think it is possible, I have got to provide pictures of existing walls so he can find match bricks.

He said although they normally provide them on a fibreglass sheet. Mine will probably be mounted on Marine Ply.

As I want to have a breathing construction I asked how would it work? he stated that the base of the wall would have a gap in it which had a insect resistant gauze that would allow moisture out,

the Sections of Brick-slips apparently slot on over timber that is on the face of insulating cladding.

If its as easy as he says would this be ideal for DIY,

my wife is not keen at this.

look forward to replies

External insulation - any pitfalls?

CWatters — Mon, 23 Mar 2009 15:37:24 +0000

Bit technical but perhaps worth a read..

"A Study of Air Movement in the Cavity of a Brick Veneer Wall"

http://www.kuleuven.ac.be/bwf/projects/annex41/protected/data/CON%20Apr%202007%20Paper%20A41-T4-C-07-1.pdf

The Belgians know a thing or two about bricks and brick slip systems. Perhaps worth a trip to see how they do it.Try the huge building show Batibouw (in Brussels), or the Green Expo (at Ghent I think).

Slips bonded to insulation...
http://www.vipplus.be/content/vds_vipplus/site/19597

I saw two old detacted houses totally transformed by the addition of a brick slip skin when we lived there. They didn't attempt to match the old dirty bricks - they went for better quality finish that looked like hand made bricks. When finished they looked like brand new houses. Not sure what system they used but it looked like the insulation board had registration holes for the brick slips to be glued into. They were pointed later.

Also found this UK system that puts slips over insulated formwork walls (eg slips over Beco wall).

http://www.padipa.co.uk/

I can't see why that wouldn't work over other types of insulation like Celotex cladding?

External insulation - any pitfalls?

fostertom — Thu, 16 Apr 2009 18:50:45 +0100

Fake brickwork finish - I think http://www.sas-europe.com

External insulation - any pitfalls?

jamesingram — Thu, 16 Apr 2009 18:57:13 +0100

got any ball bark figures per m2 on thro- colour render supply only, anyone
cheers
Jim