# External Vs Internal Insulation



## Phil_space (5 Mar 2008)

Have searched through other posts but have not seen an answer to my question below. 

I am planning a full renovation and small extension of a 1950s detached dormer and want to insulate the house beyond current building regs. Because of the age of the house there appears to be only a 2" cavity which was filled with polystyrene beads prior to my purchasing the house.

Was initially planning to insulate internally with Kingspan/Xtratherm on the external walls. However, have concerns about health issues in relation to these materials as I have heard that they have been banned from such use in some European countries. However, to reach low u-values I would need a large depth of alternative insulation, e.g. hemp, sheep's wool, which will significantly reduce my room area. I have looked into external insulation (outsulation) options but at 120 euro plus vat a m2 supplied and fitted it's a very pricey alternative. I know it's a common approach on the Continent but has any AAM subscriber actually fitted external insulation? Is it worth the money?

I am taking off the roof and replacing the floors so am happy that I can achieve appropriate u-values there but am worried about the walls and the corresponding dangers of thermal bridging. Have thought about using Poroton blocks for the extension but that won't solve my problems with the existing structure.

Any advice appreciated.


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## cgc5483 (5 Mar 2008)

Phil_space said:


> I am planning a full renovation and small extension of a 1950s detached dormer and want to insulate the house beyond current building regs. Because of the age of the house there appears to be only a 2" cavity which was filled with polystyrene beads prior to my purchasing the house.
> .


 
Just be such that there it is actually a cavity wall.  Much of the building in the 1950's was block on flat or solid concrete without any cavity,


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## Phil_space (6 Mar 2008)

Yes I'm satisfied that there is a cavity and it has been filled. I had to replace a window a couple of years ago and the place was covered in polystyrene beads for days.


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## dmac (6 Mar 2008)

The insulation material that Kingspan/xtratherm and Quinn make is PIR polyurethane and it is not going to be banned in any european country, other insulation materials such as PUR and EPS which are used on mainland europe may be banned at some stage in the future due to fire regulations, as far a PIR goes it meets all fire regulations, however its worth having a look at each companies products as some have better fire perfomance than others. Personally i have used the slab which has the PIR stuck to the back of it as well as the cavity which i had pumped with bead. In my attic i used sheeps wool as i can't stand fibre glass.


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## Phil_space (6 Mar 2008)

Cheers DMac. 

The reason I'm concerned about the PIR insulation is this quote taken from the "Teach Glas" programme - seen on TG4 - website.

_Polyurethane insulation is not permitted on the inside of buildings in some European countries as it is claimed it results in off-gassing which contributes to what is known as "sick house syndrome". _ 

I presume it refers to the chemicals in these products and how they may be released over time and this is why it is banned from the inside of buildings. 

Has the sheep's wool performed well for you? Has it compressed over time thus reducing its performance?


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## Franm (6 Mar 2008)

I've also spent many months pondering what you outline in your post. Off gasing issues, Performance of different options, Price, Loss of internal Space, Complexity at reveals, Thermal Bridging, ECO issues etc etc.
My project is the renovation of a 70s bungalow and my plan/desire like you is to insulate to above current standards.
Having said all that in the last few weeks I've decided that I'm (probably) going to go down the external insulation route and use 100mm of Kingspans Phenolic board (K5). Prices that I have been (informally) quoted for this is about 80euro per sqm not including sorting out the window cills. My BER advisor tells me that my walls will then achieve a  U-VALUE of 0.156C W/M**2K. Which is good (this includes a 50mm cavity filled with PS bead.

Kingspan tech support can supply you with the names of installers of their K5 product.

All the best and I guess realise that there is probably no perfect solution (other than possibly knock and rebuild)
Fran
ps no affiliation with Kingspan


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## Phil_space (6 Mar 2008)

Chrs FranM 

Your solution sounds good if pretty expensive. I have a detached 1 1/2 storey. Haven't calculated the wall area yet. Does your price include fitting and rendered finish or just the materials?

And yes I have also thought about the knock/rebuild route!


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## gnubbit (6 Mar 2008)

Just wondering if external insulation can be used on semi-detached houses?


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## Franm (6 Mar 2008)

Yes it includes fitting and materials. The only extra issue that I will need to address is how to deal with the window cills. Ours only protrude out 50 mm at the moment so they will need to be extended or replaced. I'm told that one can get extenders to attach to them but I think I'd prefer to replace them as I'm also re-windowing the house. Also re the square meterage I'm told that one cannot simply deduct the windows and doors from the calculation as significant "fiddly" work needs to be done on these reveals. A big window or door would get you a little price break but not the small ones. Best bet would be to estimate your sqm as a straight length by height (ignoring windows).

Not sure on question from Gnubbit re application on a semi d, I can't see any reason why not, except for the issue of where the properties join up i.e. how this step out would look. No knowledge on this though only my opinion.
Rgds
Franm


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## dmac (6 Mar 2008)

I will try and answer this off gassing question as i work in the industry and have knowledge of the process. 

All these rigid insulations have a cell structure, some are open cell while others are closed cell, All the Irish manufacturers use closed cell foam. The cells are blown with a blowing agent during manufacture. Polystyrene is blown with steam, while polyurethane can be blown with hydrocarbons, water, HFC, HCFC and certain acids etc. It is because of the cell structure and what the cells are blown with which give them there excellent insulation values. Closed cells are obviously better because they entrap the gas, over time a small amount of this gas can escape, this is where aged lambda values come into it. Every initial lambda value for all insulations is better than an aged one this is because air takes the place of the gas which can escape in some of the cells over time (off gassing), so another factor to maybe look out for is does the manufacturer have any aged lambda results.
The manufacturers overcome this somewhat by creating stronger better structured foams which will keep the gas entrapped.   
In the past 90% PIR/PUR was blown with HCFCs but under Montreal they were banned and rightly so, the blowing agents used now are much cleaner. in fact people use these same blowing agents everyday, shaving foam, and certain shower gels use a blowing agent.
I believe people are getting more exposure to them by washing and shaving than through their plastered walls.   

The sheeps wool isn't down long so its too early to tell,


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## Phil_space (7 Mar 2008)

Thanks dmac and FranM. Have spoken to Kingspan who have given me the names of two suppliers/fitters. Apparently these guys provide all of the materials as well so no chance of saving a few quid buying the boards myself. Will contact both and make a post here on how I get on.


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## Phil_space (10 Mar 2008)

Have spoken to Kingspan's recommended installers for the K5 based solution and been quoted two prices - 100 Euro per m2 and 120 Euro per m2. FranM who quoted you 80 Euro per m2?


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## Franm (11 Mar 2008)

It was a company in Cork and they supply the Weber system. He did say that Weber prices had come down recently. Having said that I've nothing in writing from them and I'm getting nervous now. Another group said to budget 35euro  +vat per sqm for the materials plus labour for fitting. (no indication yet of what labour might work out at).
I'll PM you their contact info as I'm unsure as to whether it's ok to post their contact info here


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## sas (11 Mar 2008)

Phil_space said:


> Have spoken to Kingspan's recommended installers for the K5 based solution and been quoted two prices - 100 Euro per m2 and 120 Euro per m2. FranM who quoted you 80 Euro per m2?


 
For what u-value of wall?

And to clarify, one of the Weber systems on the IAB cert IS the kingspan phenolic solution. 

Its WAY more expensive than either of their other 2 options, which incidently are still too expensive.

For anyone looking at external insulation be aware that unless you have a very simple structure the system will have big thermal bridges which negate the benefit of the system. FOr example, the roof of a bay window will be flashed up against block wall. The insulation stops at the top of the flashing which leaves a 3 - 4 inch gap where you will have absolutely no insulation and it will be incredibly unsightly. Likewise where a sunroom meets a gable wall also has the exact same problem.


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## Leo (11 Mar 2008)

Franm said:


> ... I'm unsure as to whether it's ok to post their contact info here


 
Feel free to post it so long as you have no connection other that as a customer.
Leo


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## Phil_space (12 Mar 2008)

The quotes I got were as follows:

Wetherby 100 euro per m2 + Vat
Weber 120 Euro per m2 + Vat

Both of these were for the Kingspan K5 solution. They didn't specify insulation thickness but rather asked me what u-value I wanted (0.2). However, the Wetherby guy said there was little difference in overall price in terms of the insulation thickness as the bulk was taken up with labour, fixing materials, render etc. Both of these companies seem to have a lot of experience in this area but primarily in the commercial building sector.

Whilst the Ext. Insulation option is expensive, I have been weighing it up against the cost of doing it internally, plus the loss of internal wall space with the latter solution. As I'm mainly renovating I need to retain as much internal wall space as possible.

However, I'd still be v. interested in hearing from anybody who has gone the external insulation route to see how it performs.


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## Franm (12 Mar 2008)

I'd also be interested in hearing about anybodys residential external insulation experiences.

And I also wonder how much the alternative drylining option might be by the time you factor everything in such as, 
timber required, (for batten system)
services modifications (move rads, relocate electrics etc)
Insulation cost
Plasterboard & Finishing, painting etc
Not to mention the disruption in every external walled room of your house, loss of space and all that dust.
And, time to complete the project.

i.e. if planning on installing 100mm of insulation.

Just my thoughts (but I'm not a builder or trades person)
F.


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## Branz (6 Jun 2008)

sas said:


> For what u-value of wall?
> 
> And to clarify, one of the Weber systems on the IAB cert IS the kingspan phenolic solution.
> 
> ...



There is a need to distinguish between ugliness and Thermal Bridging.

I accept that  the flashing associated with protrusions such as bay windows or extensions will make it a bit trickier but to say that they 





> negate the benefit of the system


 is a bridge too far.

A man walked on the moon in 1969, this is 2008 so it can be done.

Re doing a semi-D it can be done at the front, I have a picture of one done in Germany which I will post later


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## sas (6 Jun 2008)

ircoha said:


> There is a need to distinguish between ugliness and Thermal Bridging.
> 
> I accept that the flashing associated with protrusions such as bay windows or extensions will make it a bit trickier but to say that they is a bridge too far.
> 
> ...


 
I'm sticking to what I originally posted. The IAB cert 06/0260 figure 11 clearly shows a significant cold bridge where there is no insulation at all where the flashing is done. This will negate the performance of the EWI over standard cavity wall insulation with its associated bridging issues in my opinion. I was speaking in terms of new build. On renovations EWI may be the best of limited options.

Seeing as I'm interested in EWI I'd love if you could describe how the detailing should be done to avoid this bridge.

I've seen the pictures of EWI done on semis also. The pictures don't give any indication however as to how well it's actually performing. Again, it may simply have been the best of a limited lot of renovation options.


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## Branz (9 Jun 2008)

[broken link removed]

is the link, and figure 11 is on page 11

You write that



> The IAB cert 06/0260 figure 11 clearly shows a significant cold bridge where there is no insulation at all where the flashing is done.



What you omit to add is that the diagram specifically says that the lower roof details are by others so there is nothing 





> to clearly show a significant cold bridge



Figure 11 is about how the detail is finished off with a fire stop etc



> The pictures don't give any indication however as to how well it's actually performing.



The same applies to all building construction methods in the absence of thermal imagery


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## sas (9 Jun 2008)

The diagram I referenced in the IAB cert is titled "Detail Section - Stepped Gable".
The main detail of a stepped gable is the flashing detail, this is the point of the diagram in my opinion. 
The firestops are covered by the 2 previous figures titled "Vertical Fire Stop" and "Horizontal Fire Stop". 
THe fact that a fire stop is shown as part of figure 11 is because it's a necessary above the stepped gable.
It is most definitely not the main point of figure 11 though. 

The statement "Flashing and lower roof construction all by others" is self explanatory. External insulation suppliers
don't usually construct the roof. This includes flashing work. I don't believe an individual is building 
in compliance with the certificate if they deviate from figure 11. 

I've spoken to Weber, Greenspan and STO about their systems and all admitted that the stepped gable detail is an issue 
and none could tell me how to resolve it. 

If you are so sure that its possible to avoid this bridge then I again ask you to please describe how it's done because I need to know.

You claimed that external insulation can be done on semis because you saw a photo of it. My point was that just because
someone did it and took a photo of it doesn't mean that it is actually efffective. The attached house becomes
the weakness in the insulation envelope when this is done. If it's poorly insulated it will happily conduct away the heat.


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