External insulation choices

[JohnH]

Hi
My neighbour and I are contemplating installing EWI as a DIY project. We have two 1930s semis with solid walls and pebble-dashed that we are at this moment getting in quotes for applying external render. The quotes are coming in at around £11K per house with VAT at 5% plus scaffolding. This is too expensive for our liking and this is on the assumption that some the work would be done by ourselves:
Boxing in soil pipes with concrete weather board with access points.
Fitting extensions to window cills and roof verges.
Removing drainpipes, gates, awnings and satellite dishes etc.
In order to adhere to the 2010 Editions of Approved Documents L to the Building
Regulations, a minimum thickness of 55mm Kingspan K5 would need to be used. This would give a U value of 0.29 or 0.28 for 60mm.
I would be interested to know if others have done polymer resin/phenolic external insulation as a DIY.
JohnH

[wookey]

JohnH: Just to clarify: that's 11K just for the rendering, including the render? i.e the insulation would be extra? For DIY, some people on the Green Building Forum have experience: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6967

[JohnH]

Wookey- Thanks for this, just what I need.

The £11K quote is for the render and 50mm phenolic insulation although the quote doesn't say what this is.

JohnH

[wookey]

How many square metres are your walls? £60/m2 is about as good as it gets for EWI, but 80-100 seems more common. 11K sounds reasonable to me. I'd guess that was around £95/m2?

50mm phenolic is thin-but-expensive insulation. EPS is usually somewhat cheaper but needs more thickness for same insulation value.

[JohnH]

Wookey
The area as measured by the contractor is 132M2 which sounds rather high for a three bedroom semi.
If £11K sounds reasonable don't forget we are doing the preparation work ourselves. As I mentioned, apart from removing gutters, drainpipes, sat dishes, exterior sockets, gates, etc they have all got to be put back. This entails fixing raised 100mm mounts to the walls before the insulation is applied.
My neighbour who is a carpenter/DG specialist will extend window cills, roof verges and make good all windows and doors after the insulation has been applied.
You're right about the phenolic insulation as Kingspan K5 60mm works out about £1650 plus VAT for the measurements given.
JohnH

[wookey]

Which is why EWi is normally done with EPS or rockwool, because cost/m2 is usually more of an issue than overall thickness.

[pb]

What render system are you using?  £11k doesn't sound like an outrageous price for rendering and insulating that sort of area.  If you're using a thin-coat render (acrylic, silicone etc) then the materials are quite expensive.

Insulation-wise, generic 75mm PIR board seems to cost about £8/sq m at the moment, so maybe £5-£6/sq m for 50mm.  Probably a bit more for Kingspan or Celotex branded stuff.  If the thickness isn't a critical issue then it might well be more cost-effective to use a slightly thicker layer of cheaper board rather than pay a premium for the absolute best lambda value.  As Wookey said, XPS seems to be a popular option for external insulation, both for cost reasons and because you can (under some circumstances) render onto it directly.  I wouldn't use rockwool unless you are very confident about it not getting wet, which probably means an extra layer of breather membrane.

If you need a cement board cladding to render onto then that could easily cost another £5/sq m.  Plus then you probably battens, head/foot tracks and suchlike to carry it (maybe £0.40/m for timber, double that for proprietary metal fittings).

If you're prepared to do all that preparatory work yourself then you could consider fixing the insulation (and carrier boards, if you're using them) and then just getting a plasterer in to apply the actual render on the outside.

[JohnH]

PB-Thanks for the information.
The render system quoted so far is Weber, but I have PermaRock quoting shortly.
Thickness is an issue here unfortunately because it would involve re-routing drainpipes, gutters, sockets as well as somehow making good around doors and large bay windows top and bottom. We will probably pay the extra for Kingspan K5 to conform to part L as I don't want Building Control on my back.
I managed to measure the outside walls of just my house and it is 121M2 including the doors and windows and I am at present making up a drawing.
JohnH

[pb]

Oh, right, I hadn't really registered that you were using the K5 wallboards.  That probably is a good reason to use Kingspan since I don't think the cheaper manufacturers tend to offer that configuration.

As far as actual insulation value goes the gap between the different suppliers is really quite small, and probably not going to make the difference between meeting part L and not.  I think K5 has lambda 0.021W/mK or so, which is the same as Celotex 5000-series.  Recticel and Ecotherm are very slightly worse than that, with advertised lambda something like 0.022W/mK.  If you're only installing 50mm of the stuff then the difference probably isn't worth worrying about, and almost certainly not something that building control are going to get excited over.

Render-wise you might like to take a look at WBS and JUB if you haven't already.

[MTownshend]

Our house is solid 9" brick with a cavity skirt to about 3' above ground.
When we had the extension put on the side we had 100mm EPs insulation fitted to the existing house (and the front of the extension, to keep it neat)
Price was cheaper than 50mm of phenolic and the windows all look find with the deeper reveals.
The EPS was bonded on, then a fibre mat bonded to the EPs then a maintenance free base, and render finish on top.

Still looks great 21/2 years later.

Our eaves were open, and overhung a long way so the insulation thickness was no problem.
Eaves are now enclosed with vents in.

Price was around £8k IIRC.

[M]

Hello guys and gals. I read a thread on MSE recently about troubles with external insulation. Poor Shazza, is suffering from the down sides of the insulation. Hopefully by the end of the Summer, she and her family will have a much better home. But thought it might be useful to post some of her comments, if only to help people decide on the best time to install.

Shazza’s home is suffering from evaporative cooling, bit like living in a fridge. I know next to nothing (compared to you peeps) about this, but does this suggest that the best time to install is late Winter, ready for Spring and Summer to help dry out the house?

Shazza said I could cut & paste her posts. Haven’t asked / posted the others, but her replies are pretty self explanatory.

As the insulation is doing its job, moisture is finding all the cold spots in the house. Great fun for her. She’s got her fingers crossed for a long hot Summer.

This post mostly for information, but Shazza will be watching, so any extra tips, would I’m sure, be greatly appreciated.

Thanks. Apologies if it’s a bit long. Martyn.


Hiya all,
We have had external wall insulation put on our house, it was like polystyrene blocks that were attached to the walls then skimmed over, does anyone know anything about this kind of insulation plzz

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I’m asking after it has been done because our LHA have done this to the house about 6 months ago and dont know much about it.

i do know that it has caused a lot of problems inside the house.
my bathroom ceiling is now black with mold, the DG windows are steamed up and theres condensation running down the walls 

we are definately in a polystyrene box which is bad because we can now hear everything my neighbour does i.e. closing doors, talking on the phone etc etc, its the worst thing ever and wished it had`nt been done 

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Some of the neighbours have reported similar problems to LHA and have been told to open the windows..which is ridiculous at this time of the year and seems a bit of a condradiction to the insulayion in the first place.
The mold first appeared on the ceiling above the extractor fan and has now moved to above the window(which is usually open just a smidgen), we have lived in this house for 18 years and have never had problems like this before, so it must be the insulation thats causing this.
As for the noise, it could be because we live in a semi and with both houses being done its like ecky119 says "polystyrene box" everything seems to be echoing within the box  and tbh its an absolute nightmare as my neighbour is a night owl so tlks on the phone and bangs his doors til 2 am..

Hopefully the weather will warm up and we can open the windows but North winds r cold up here so it may be a while.

Thanx for the tips and we`ll see what works for us

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Tbh the house feels colder but with gas prices as they are we cant afford to have the heating on much, so we dont seem to be feeling any benefit.
I have noticed the house is a lot colder through the night than its ever been. All these differnces and problems are why i was wondering whether this type of insulation has caused similar problems to anyone else. We were sent a letter about the work starting but no-one explained anything about it, and i dont really trust the LHA as they just seem to make excuses for everything.
thanx for replying,

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I`m thankful for any help on this because its a nightmare to live with. I`m just a housewife/mother so havent a clue about insulation etc, the only thing i can say is our upstairs ceilings have slanted bits where the roof goes down(i`m sure theres a name for them) thats where all the condensation and mold is, reading what jim says i`m wondering if theres no roof insulation in them bits of the loft.
i know there is a lot of it up there but dont know if it goes to the slanty bits. Thanx for info.

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Just put a pic of the ceiling on my facebook and already 3 of my neighbours have said they have the same problem, and worse is 2 of them have had the LHA out and have been told its not mold its condensation, 1 was told to open all the upstairs windows to let the air circulate..

Looks like nothing will be done 

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You`re not being rude just honest. I think what i`m trying to get across is the fact that the LHA installed this insulation about 5 months ago and now my bathroom ceiling is black and i have condensation running down the walls upstairs, downstairs is fine.
We are on a very low income so cant have the heating on much so opening windows is a no-no, and theres no way we could afford to redecorate every few weeks.Just come off the phone to the LHA and they have agreed to send a joiner out to check the insulation where the skeilings are, so will see what happens then.

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Haha Ken lucky you, we didnt have a choice and if the council wont help with the problems the house will have fall apart, if we follow their advice on how to control it, it means spending over half of our income 

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youre right whasup, in bed i am really warm, pj `s sticking to me but when i get out of bed its absolutely freezing, the house does actually feel colder and tlking to neighbours/friends in the area are saying the same..but i am being told to open windows and theres no way i can open more than 1..its already costing me £50-70 a week on gas and leccy, when considering our income is £120 a week. we cannot afford to put the heating on to make up for the cold that comes through the open window so its a no win situation imo

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haha i live in northeast england so we never have a long hot summer, we r lucky to have a summer at all !!
after my facebook post my neighbours and friends have set up a "mould " group which we have posted each others pics of the mould. I`ve had people here today taking pics and notes and i showed them the group pics, they were shocked as mine is nothing to what some have got. A lot of them have got the mould in the bedrooms which is worrying (lucky for me mine isn`t YET), so it seems that there is a problem somewhere.
These houses were temporary houses built either in the war or just after and are what people call "non standard" construction i think, basically they are concrete. We had cavity wall insulation fitted years ago, we have double glazing and about 4/5 layers of insulation in the loft.

anyway it looks like gentoo (LHA) are listenng and hopefully will find an answer,
thanx for all your advice. hints etc and will keep you posted to what happens.

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our info was very useful, when i mentioned it theres now someone coming out to check the skeilings on Monday   it has also come to light that the extractor fans have no tubing (or whatever its called) going outside so basically just a hole in the wall, which they took pics of. And my house is like a fridge its freezing cold in here, so hopefully i will be sorted or i win the lottery and go and live somewhere warmer lol 

[A.L.]

hello,

yes the 'skeilings' will probably not be insulated, the water vapour condenses on these cold surfaces and mold grows in the damp conditions

the EWI probably reduces external noise coming in and makes other noises more apparent, i am no acoustics expert but the EWI may possibly contain the sound energy which would have escaped and direct it, increasing the 'flanking' transmission

also it would be informative to find out wether the polystyrene was XPS (extruded) as this would retain water vapour or EPS (expanded) as this would breathe

it would be interesting to find out the name of the non-traditional construction as concrete ones suitable for cavity fill are unusual

[dhaslam]

That is quite a strange example.   It seems like the attic insulation wasn't upgraded  or doesn't exist  so there is little temperature  gain  or noise reduction and  the reduced area  of cold surfaces means more condensation  on the what is left.   

[SpeedEvil]

In short - take a badly insulated, drafty, underheated building, wrap parts of it in polystyrene, and vastly improve the air-sealing.
The tenant still can't afford to properly heat it - so it stays underheated, maybe not quite as much as before - but the airflow is drastically reduced.

This means that the normal water released into the flat now can't be ventilated away as it was before, the humidity shoots up, and the condensation on the slightly colder bits is huge.

Heating will reduce mould. As will ventilation.

Pretty much any property, if not heated to >15C or so will have some parts of it where moisture will condense.
Unless it has lots of airflow.

[Shazza2012]

ok A.L.
All i can say is the house was built as temporary housing either during or just after the war, they are concrete. we think it was some sort of metal structure which was then filled with concrete.

no-one turned up to check the skieling insulation today so looks like another phone call 

would also like to add that my bathroom skieling is black even tho we have an extractor fan and open the window, so i`m at a complete loss..

thanx for your replies and thanx Martyn for all your help

shazza