# Opinion on proposed cavity wall insulation make up



## jonnykerry (13 Dec 2013)

Hi all,

After loads of research and consulting with my engineer, we have come up with a insulation make up for the cavity wall in my house which is starting in January (Finally!) 
The house will be built on a insulated raft with a 200 mm cavity (150 mm internal/ 100 mm external block ground floor & brick exterior and 100 mm block for upper floors) 

To get to the point due to the upper exterior being brick, bead insulation looks to be not an option (correct me if I'm wrong) as the house will be in Kerry, So what we propose is to use 140 mm areobord full fill insulation set to the outer part of the cavity with 50 mm of foam (Basf Walltite) injected to the remainder part of the cavity. 

Provisionally it gives a "real world" u-value of 0.138, an airtight seal on inner wall from foam and at the wall plate the whole cavity (down 400/500 mm) will be foam to provide stability to the cavity.
Secondly there will be a MHRV primarily for air quality and secondly to remove moisture due to the fact the foam is none breathable as far as I understand.

Any opinions very welcome or other options


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## lowCO2design (13 Dec 2013)

jonnykerry said:


> insulated raft. 200 mm cavity (150 mm internal/ 100 mm external block ground floor & brick exterior and 100 mm block for upper floors)
> upper exterior being brick.. 140 mm areobord full fill insulation
> set to the outer part of the cavity
> with 50 mm of foam (Basf Walltite) injected to the remainder part of the cavity.
> ...



 grand cavity insulation downstairs & i get the rigid board upstairs subject to quality of block layer & details.
maybe consider going with the board through-out (just due to the brick & just to reduce the variance in the detail.
set to inner side of inner block wall
?? dont agree with this. show us where in the BBA it show this use?
leave out the foam, consider this instead [broken link removed]
air-tight? show us where the BBA say this?? air-tightness would be best dealt by plastering the internal wall
???? does you structural engineer know what he's doing? this is what gives stability to the cavity wall-tie
mvhr's primary requirement in an air-tight house is is for ventilation
VOC's Volatile_organic_compound will be emitted from over 90% of the materials you put into your new home - why pick-out the foam in particular? Furniture, Paint, plasterboard, Bedding, Paint strippers, Adhesives/glues,  Solvents, Upholstery and other textiles, Carpet, Cleaning products, Electronic equipment.. etc


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## jonnykerry (19 Dec 2013)

Hi Low C02,

Thanks for the informed reply. 
Had a look at the Thin-R-CT-PIR, grand insulation but just have serious reservation's about it's full life insulation values when it is going to be constantly getting wet due to brick work weeping due to being on the west coast!

So I know it's not as good inch for inch but I think the aerobord is the best long term bet.

In regard to the foam I talked about it is Basf walltite and "sitting on the fence" it looks to be a good product but it is closed cell, thus why I stated the MHRV would be vital as my understanding is that it will prevent moisture moving from the inside of the inner block work to the cavity, so the MHRV will play a important duel role= fresh air and prevent damp on inner wall's.

You don't know of a full fill aerobord type insulation that would give a better u-value.

Thanks for your help.
Jonny


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## lowCO2design (19 Dec 2013)

jonnykerry said:


> Hi Low C02,
> 
> Thanks for the informed reply.
> Had a look at the Thin-R-CT-PIR, grand insulation but just have serious reservation's about it's full life insulation values when it is going to be constantly getting wet due to brick work weeping due to being on the west coast!


 ok go with a wide cavity and pump it with grey bead


> So I know it's not as good inch for inch but I think the aerobord is the best long term bet.


ok, suit yourself, so why ask the following : 





> You don't know of a full fill aerobord type insulation that would give a better u-value.


 EPS is 0.034wmk approx with PIR/PUR in the region of 0.023wmk thats it! take it or leave it





> In regard to the foam I talked about it is Basf walltite and "sitting on the fence" it looks to be a good product but it is closed cell,


 it is not a good product for installing in a cavity. and you haven't shown me where in its certification it does any of things you stated in the OP





> thus why I stated the MHRV would be vital as my understanding is that it will prevent moisture moving from the inside of the inner block work to the cavity, so the MHRV will play a important duel role= fresh air and prevent damp on inner wall's.


 rubbish (sorry but there's no other word for it)


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## jonnykerry (20 Dec 2013)

G's you certainly shot from the hip Mr. C02 .

First off in regard to "certs" the bead insulation is not certified for brick work in exposed area's..

"You don't know of a full fill aerobord type insulation that would give a better u-value."
You miss understood me as I meant is there any other company that supplies a similar EPS full fill board wider i.e. 250 mm, thus giving a better u-value

And finally before you cut me with regard to my view on the MHRV, please bare in mind I ain't a "house basher" dreamer or clown, just because I ain't preaching on this form like other's doesn't mean I don't know what I'm talking about. I'm an Engineer and time served trades man, and the MHRV would reduce the risk of condensation somewhat.

Thus why the idea of combining the aerobord with the foam as in my view it would resolve any issue with thermal looping and provide a respectable u-value. best of both worlds economically. i.e engineering to a budget.

If you do know of a bead fill that has a cert for exposed area's I'd be grateful if you could forward the details.

I do appreciate your views.


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## lowCO2design (20 Dec 2013)

show me the IAB/BBA cert for foam in a cavity?

if you need mvhr to: 





> prevent moisture moving from the inside of the inner block work to  the cavity, so the MHRV will play a important duel role= fresh air and  prevent damp on inner wall's.


 (when you are building a new structure) you need to study up on thermal bridging & interstitial condensation 

why would you install a 250 cavity ? and state the above?

forget your aeroboard fixation


and what does this mean?


> bare in mind I ain't a "house basher" dreamer or clown, just because I  ain't preaching on this form like other's doesn't mean I don't know what  I'm talking about. I'm an Engineer and time served trades man


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