Using foam in wall cavity for new build

froshtyv

Hi,

I have read a few older threads on here where using foam was not recommended, is this still the case?

I am doing a self-build with a proposed cavity of 150mm.
I had originally planned to use beads and an air-tight tape around windows etc.

I then looked at using foam as it would fill any potential gaps at windows etc and have better airtight properties compared to beads thus reducing the amount of air-tightness required around windows and doors.

I am not chasing any air-tight figures any where between 1 - 2 m3/(h.m2) i would be happy with.

Any pros or cons on the above would be appreciated.

Just to add, it would be Walltite that i would be looking to use.

BryanF

Have you priced it?

froshtyv

BryanF wrote: »

Have you priced it?

I haven't yet, but I have been informed that is circa twice the price of beads or boards.
If i thought it was worth paying extra for if regarding its airtight benefits then I would.

BryanF

IMO,
It’ll be more than twice the price. And when you weigh up the pros and cons there are better ways of insulating.

I’ll say no more this has been covered to death.

froshtyv

BryanF wrote: »

IMO,
It’ll be more than twice the price. And when you weigh up the pros and cons there are better ways of insulating.

I’ll say no more this has been covered to death.

If you have links to some recent threads worth reading that would be great.
The ones I came across were 2008 or 2011

Dudda

Foam looses it's airtight properties over time. While you might get a good airtight test result once finished it would be a different story after a few years particularly if you don't use airtight tape around the windows and doors.

JonathonS

Dudda wrote: »

Foam looses it's airtight properties over time. While you might get a good airtight test result once finished it would be a different story after a few years particularly if you don't use airtight tape around the windows and doors.

Hi, do you have any references that back up that information on shrinkage? I have heard it said, but never seen any study that confirmed it.

On the other hand I have seen reports on here and on other forums from users of foam and beads that said after many years there was no sign of any shrinkage.

eamon11

BryanF wrote: »

IMO,
It’ll be more than twice the price. And when you weigh up the pros and cons there are better ways of insulating.

I’ll say no more this has been covered to death.

as op stated, please provide links.

froshtyv

JonathonS wrote: »

Hi, do you have any references that back up that information on shrinkage? I have heard it said, but never seen any study that confirmed it.

On the other hand I have seen reports on here and on other forums from users of foam and beads that said after many years there was no sign of any shrinkage.

Hi Jonathon,

Have you got this far with your build? (installing Walltite in cavity)

BryanF

Ok, so

I’m going make some statements based on the above, take what you want from them

-There is no point in a new build, using foam in cavity to improve air-tightness. How and where do you link the foam layer to any other air-tightness layer?? The OP talks about sealing at windows, there will be cavity closures and structure required to retain the foam from escaping during install, you cannot achieve air-tightness using cavity foam.

-If you’re designing on paper, it’s cheaper to increase the cavity and go with beads than go with foam. ( or go with PIR boards if you are in a position to watch the builder like a hawk)

- foam is reported as air-tight & moisture resistant - you’re sealing the cavity. So what does this mean for moisture that may get into/ trapped in a cavity and needs to escape?? At least with bond bead (or boards) moisture can move down and out of the cavity, as is the traditionally purpose of a cavity.

- there is only one foam product that I’m aware of the carries the correct certs for use in a cavity. It has its uses, But IMO the risks of completely sealing the cavity, around wall ties etc is not the way to go.

BryanF

JonathonS wrote: »

Hi, do you have any references that back up that information on shrinkage? I have heard it said, but never seen any study that confirmed it.

On the other hand I have seen reports on here and on other forums from users of foam and beads that said after many years there was no sign of any shrinkage.

Show me a technical data of a foam product stating a foam is air-tight?

show me a foam (technical data sheet) states zero shrinkage over its lifespan?

Also what’s the voc’s/ off-gassing from pumping foam, and how long does this continue for?

Lumen

I was looking to use closed cell foam in my block cavity (retro fit) until I thought about wall ties and dew points.

Enclosing a corrodible structural element in a pocket of vapour impermeability, with one end warm and the other end cold, seems like a kind of dumb idea even with my school-level science understanding.

_Brian

Is it certified to use in Ireland?

Lumen

_Brian wrote: »

Is it certified to use in Ireland?

Walltite is for new build timber cavity.

https://www.nsai.ie/Our-Services-(1)/Certification/IAB130377_GOS_BASF.aspx

_Brian

Lumen wrote: »

Walltite is for new build timber cavity.

https://www.nsai.ie/Our-Services-(1)/Certification/IAB130377_GOS_BASF.aspx

But not block cavities?

Lumen

_Brian wrote: »

But not block cavities?

No. I did try and find a closed cell product certified for block cavities but couldn't find one.

froshtyv

BryanF wrote: »

Ok, so

I’m going make some statements based on the above, take what you want from them

-There is no point in a new build, using foam in cavity to improve air-tightness. How and where do you link the foam layer to any other air-tightness layer?? The OP talks about sealing at windows, there will be cavity closures and structure required to retain the foam from escaping during install, you cannot achieve air-tightness using cavity foam.

-If you’re designing on paper, it’s cheaper to increase the cavity and go with beads than go with foam. ( or go with PIR boards if you are in a position to watch the builder like a hawk)

- foam is reported as air-tight & moisture resistant - you’re sealing the cavity. So what does this mean for moisture that may get into/ trapped in a cavity and needs to escape?? At least with bond bead (or boards) moisture can move down and out of the cavity, as is the traditionally purpose of a cavity.

- there is only one foam product that I’m aware of the carries the correct certs for use in a cavity. It has its uses, But IMO the risks of completely sealing the cavity, around wall ties etc is not the way to go.

Thank you for the detailed reply, much appreciated.

Wartburg

I did a preliminary air tightness test recently in a house, where BASF Walltite has been applied as full cavity wall insulation (150mm width).
The windows haven´t been taped with additional window tape for air tightness, the highest ceilings were covered with membranes, no plaster has been applied - neither internally nor externally.
The test ended with 1.99 air changes per hour (n50) and an air infiltration rate of 2.30m³/h*m² (qE50).
There was no air infiltration through the blockwork or around the windows traceable, where the Walltite has been applied. I even taped some areas of the exterior walls with membrane upfront, to make potential air infiltration visible, but there was no ballooning of these membrane patches during the depressurization.
The most air infiltration came through perforations of the uprising radon membrane, which covers the first layer of block and continuing on top to the outside.
I can´t (and do not want) judge how good or bad this kind of insulation is in total, because I have no experience about the longterm performance and various other parameters (moisture resistance, shrinking, uv resistance, evaporation), but I have to confirm that the BASF Walltite creates an air tight layer.

Lumen

Wartburg wrote: »

I did a preliminary air tightness test recently in a house, where BASF Walltite has been applied as full cavity wall insulation (150mm width).

Which Walltite product, and was it sprayed, poured or injected through drilled holes?

Block on both sides of cavity?

Wartburg

Lumen wrote: »

Which Walltite product, and was it sprayed, poured or injected through drilled holes?

Block on both sides of cavity?

Standard cavity wall with block on both sides and 150mm cavity. I can´t name the exact Walltite product. It was the liquid one, which injected through drilled holes. There were plenty of holes drilled and the client told, the installers filled every block layer seperately. It took them a full week to fill the entire cavity. The walltite is rock-hard and grey, where it´s still visible (e.g. in the reveal).
Once again: I can´t judge how good the product is overall but it definitely creates an air tight layer, which I didn´t expect so far.

MicktheMan

Any cracking visible?

Wartburg

MicktheMan wrote: »

Any cracking visible?

Haven´t seen anything.

BryanF

Wartburg wrote: »

I did a preliminary air tightness test recently in a house, where BASF Walltite has been applied as full cavity wall insulation (150mm width).
The windows haven´t been taped with additional window tape for air tightness, the highest ceilings were covered with membranes, no plaster has been applied - neither internally nor externally.
The test ended with 1.99 air changes per hour (n50) and an air infiltration rate of 2.30m³/h*m² (qE50).
There was no air infiltration through the blockwork or around the windows traceable, where the Walltite has been applied. I even taped some areas of the exterior walls with membrane upfront, to make potential air infiltration visible, but there was no ballooning of these membrane patches during the depressurization.
The most air infiltration came through perforations of the uprising radon membrane, which covers the first layer of block and continuing on top to the outside.
I can´t (and do not want) judge how good or bad this kind of insulation is in total, because I have no experience about the longterm performance and various other parameters (moisture resistance, shrinking, uv resistance, evaporation), but I have to confirm that the BASF Walltite creates an air tight layer.

What’s the plan to link the wall foam at junctions with windows, floor, penetrations etc

Wartburg

BryanF wrote: »

What’s the plan to link the wall foam at junctions with windows, floor, penetrations etc

Probably to prevent the silly home-made cavity wall closers, made of Kingspan or a similar PIR board. I wasn´t involved in the strategy and just do the evaluation from the air tightness aspect.

BryanF

Wartburg wrote: »

Probably to prevent the silly home-made cavity wall closers, made of Kingspan or a similar PIR board. I wasn´t involved in the strategy and just do the evaluation from the air tightness aspect.

Sorry what’s the air-tightness connecting material

BryanF wrote: »

to link the wall foam at junctions with windows, floor, penetrations etc

Wartburg

BryanF wrote: »

Sorry what’s the air-tightness connecting material

No additional air tightness layer like tape, membrane or paint around the windows. The gap between the window frame and the block was completely filled with Walltite. Unfortunately I didn´t take photos myself - was too astonished about the performance.