Third picture - these forums don't seem to display the picture 90 degree rotated, and just turn it back!

Posted By: mikaelHowever after I started, I found that the PU foam shrinks when it cools and can cause significant damage to the masonry. BASF walltite seems a bit worse than other foams, which I also tried.

That seems like a fairly fundamental indictment of both the BASF product and the BBA quality assurance process. What do BASF have to say about your problem?

Posted By: djh

Posted By: mikaelHowever after I started, I found that the PU foam shrinks when it cools and can cause significant damage to the masonry. BASF walltite seems a bit worse than other foams, which I also tried.

That seems like a fairly fundamental indictment of both the BASF product and the BBA quality assurance process. What do BASF have to say about your problem?

Good question. I took it up with BASF and Isothane (both have had issues). They either blame the installer not installing it right, or just bad luck. Isothane said that if you install it right you don't get any issues. However I believe BASF have had legal action taken against them in Ireland. BASF also visited my site and checked a foam sample coming from the installers equipment and they said it was good. I have also contacted the BBA and they don't seem to wish to discuss exactly what testing they did. However I recently contacted them again to discuss it and I asked them if they tested the foam in a simple straight wall, or whether it had any returns or corners in it. They stated it was probably a simple straight wall. I pointed out that this would not be a good test to verify possible damage in corners, and they said it was something they would look into.

Personally I just think it is an issue that is inherent in how these foams have to work. The curing involves an exothermic reaction and the temperate in the curing foam gets quite high. Being such a good insulator it takes quite some time to cool. The foam cures and sets whist the gases from the blowing agent are hot. The blowing agent is trapped in million of little cells and it will contract when it cools. The contracting gasses forces the cells to shrink a little, and as we all know, expanding and contracting gasses can exert huge pressures, especially over a large surface area. PU foam bonds very well indeed to masonry, so it just moves it, if the masonry can no longer resist the forces being exerted.

I have recently found a foam used in the US which is basically a phenolic foam which is poured and it produces no heat during the poring and setting process. It has a lamda value roughly half way between open and closed cell PU foam, and is 70% closed cell. I am looking into getting this to construct a roof by fully filling the voids between and through open web joists used as rafters. I would hope that this type of foam would not suffer from the same problems that the closed cell PU foams suffer from.

Posted By: gravelldOff the topic of wall ties but...

Walltite is advertised for use in hard to treat cavities though. Surely they would've had trouble before?

There's also Retrofoam and... icynene?

Well if you speak to installers who have used walltite, quite a few have had experienced problems. The problem is more pronounced when larger cavities are filled, as there is greater heat build up and more initial gas expansion, and a more significant amount of shrinkage.

I have been doing some research on Retrofoam, but have no experience with it. However I have seen quite a few reports that Retrofoam also shrinks, but it does not cause any damage as it does not have the strength or adhesion, but instead can collapse causing voids in the area insulated. Icynene is an open cell foam and it may not be ideal in a cavity as it could absorb moisture, but they do a pour fill version, so someone who is happy to take a punt could try it. Both of these possible alternatives also have a much higher lambda value too.

Posted By: mikael

Posted By: djh

Posted By: mikaelHowever after I started, I found that the PU foam shrinks when it cools and can cause significant damage to the masonry. BASF walltite seems a bit worse than other foams, which I also tried.

That seems like a fairly fundamental indictment of both the BASF product and the BBA quality assurance process. What do BASF have to say about your problem?

Good question. I took it up with BASF and Isothane (both have had issues). They either blame the installer not installing it right, or just bad luck. Isothane said that if you install it right you don't get any issues. However I believe BASF have had legal action taken against them in Ireland. BASF also visited my site and checked a foam sample coming from the installers equipment and they said it was good. I have also contacted the BBA and they don't seem to wish to discuss exactly what testing they did.

It's a difficult situation, I suppose. Obviously, everybody is worried about the consequences if they are proved wrong. But whilst it is expensive to prove that a building sytem works, it's even more expensive to prove that it doesn't, so the odds are somewhat stacked. So good on you for finding a solution that worked in your situation.

I don't know what the right answer is. I suppose initially, it was the building's owner that took the risk, then maybe some rich owners were able to pass most of the risk to the master builder. But the system we have now seems to be too complicated, although I have no idea how to improve it. I am grateful that our regulation system does at least allow some experimentation. But I think 'caveat emptor' applies just as much to building techniques as it does to property purchase.

Posted By: djh

But I think 'caveat emptor' applies just as much to building techniques as it does to property purchase.

Hmmm... I think it depends on who the risk is shifted to. It seems to be ok for manufacturers to scream "caveat emptor", backed by testing regimes in which we continue to see issues.

But if one of us individuals wants to insulate a plinth? Then you're in the BCO lottery.

FWIW, I came across this for installation - this is of the spray applied version, which may have a higher total and/or faster heat production - but the comments on total depth of insulation:

"Do not apply Walltite V.3 in excess of 50mm (2”) depth per pas due to the products exothermic effect. After spraying a pass, cooling time, must be allowed for the dissipation of heat before spraying another pass. Not allowing adequate cooling time raises the risk of scorching and/or fire and affects product mileage.

Walltite V.3 regular grade: after applying the first pass, wait until at least 10 minutes before applying a second pass. If a depth of more than 10mm (4”) is required, wait at least 1 hour before applying a third pass. If a fourth pass is required, wait at least 1 hour before applying it. A maximum of four passes to a total depth of 200mm (8”) can be applied in a 12 hour period.

Walltite V.3 F (fast): after applying the first pass, wait until at least 10 minutes before applying a second pass. If a depth of more than 10mm (4”) is required, wait at least 2 hours before applying a third pass. A maximum of three passes to a total depth of 150mm (6”) can be applied in a 12 hour period.

Walltite V.3 CT (Cold Temperature): after applying the first pass, wait until at least 1 hour before applying a second pass. A maximum of two passes to a total depth of 100mm (4”) can be applied in a 12 hour period.
"

https://niagarafalls.ca/pdf/tenders/1613/specifications.pdf

I really hate the vapour barrier on the cold side of the insulation and can only see this leading to problems, sorry.

Posted By: TimSmallThanks for the interesting comments and photos mikael. I suppose with a 300mm cavity you'll have about 4x the total shrinkage (at least - more if thermal effects are greater due to the centre reaching higher temperatures) vs a 75mm retrofit cavity.

Was all the pouring done from the top? What height of foam did you fill in each foam "lift"? How long between the masonry being completed?

I think I'd be a bit cautious about using phenolic due to water absorption? Not that I know much about it - just that Kingspan Kooltherm acts like a sponge (as does the green foam that florists use to stick flower stems in - because it keeps the flowers well watered - which is also phenolic), but perhaps this can be overcome with different phenolic foam types or additives?

With a 300mm cavity, did you consider using rigid PIR boards instead of polythene sheet against the outer (or inner) face (e.g. 200mm PIR boards, and 100mm insitu foam)? Since the in-situ foam would then stop the thermal bypass which is the main drawback of PIR-in-cavity-wall.

Only makes sense if PIR board is cheaper per unit volume than the foam I suppose, but would get you a slightly higher U value for a given wall thickness ("mid life" λ value for a full sheet PIR 0.023 W/m²·K, and long term λ value of 0.026 vs. 0.029 W/m²·K for the insitu foam).

Graphite EPS, or even mineral wool would also be worth considering I suppose?

You are right to mention the cavity width. The larger cavity will most certainly exacerbate the problem of shrinkage. Nonetheless, the shrinkage is significantly more than the manufacturers claim it should be. Technithem and Walltite are both certified for use in cavities up to 200mm. I used it initially on the basement cavity walls which have a 200mm cavity and I got serious issues. When I had first considered using foam, I had contacted BASF and they said 200mm would be fine, but with 300mm I would need to fill the cavity very slowly. In reality 200mm was not fine, and based on that experience I was not even going to attempt to use the product without providing a mechanism to allow it to shrink.

Initially I had generally waited about 3 week at least before foam was poured in. The maximum height of pouring was about 2m, but in most cases about 1.5m

I also have the same reservations as you with phenolic foam, so it is not something I would want to use in a masonry cavity wall without finding out more about it!

I had indeed considered using 200mm rigid PIR boards + 100mm foam for my 300mm cavity, but I came to the conclusion that the getting the boards to seal nicely around all my check reveals would take quite a bit of work. Also boards are more than double the price of the polyurethane chemical. The cost saving is often absorbed by high labour rates factored in by foam installers, but I found a one very local who was happy to just charge me for his time rather than inflating the price by quoting for a whole job.

Your point about slight differences in Lambda values between in-situ foam and manufactured boards is worth noting, but I'm not sure how much difference there is once the foam and boards have aged a bit, they are both significantly better than mineral wool or eps (even graphite eps)

Posted By: TimSmallI think I'd put in something other than polythene on the outer face (e.g. EPS or mineral wool) as a vapour open debonding layer.

I'm not quite sure what the concern is? The PU foam is presumably vapour impermeable, so there won't be any condensation on the polyethylene, but even if there was, so what?

But if you're paranoid, then why not use perforated polyethylene? It's apparently available in rolls.

Posted By: mikaelI am not too concerned about the polythene used as the debonding layer as the foam is pretty much impermeable anyway, so facing it with another impermeable layer should not cause a problem.

I don't think that's right - the µ value (water vapour diffusion resistance) of polyurethane foams is around 30 to 200 depending on the composition (60 is often quoted).

The µ value of polythene DPC membranes are around 100000.

For comparison most timbers have a µ value of about 20 to 50.

I've seen fully saturated polyurethane foam insulation boards taken off an old "warm roof", and I've also seen wufi simulation results for green roofs where the polyurethane slowly fills up with water from the top down (over several years).

Water vapour diffuses more quickly at higher temperatures, and this can result in moisture "piling up" on the cold side if there is a high resistance layer on the outside.

Because absolute humidity is nearly always higher inside a home in the UK climate, it would be safer to use something which is relatively more vapour open on the cold side of the cavity.

e.g.

PIR foam µ = 60
EPS µ = 60
mineral wool µ = 1

Bricks and blocks have µ between about 10 and 150

Posted By: TimSmall

Posted By: mikaelI am not too concerned about the polythene used as the debonding layer as the foam is pretty much impermeable anyway, so facing it with another impermeable layer should not cause a problem.

I don't think that's right - the µ value (water vapour diffusion resistance) of polyurethane foams is around 30 to 200 depending on the composition (60 is often quoted).

The µ value of polythene DPC membranes are around 100000.

For comparison most timbers have a µ value of about 20 to 50.

I've seen fully saturated polyurethane foam insulation boards taken off an old "warm roof", and I've also seen wufi simulation results for green roofs where the polyurethane slowly fills up with water from the top down (over several years).

Water vapour diffuses more quickly at higher temperatures, and this can result in moisture "piling up" on the cold side if there is a high resistance layer on the outside.

Because absolute humidity is nearly always higher inside a home in the UK climate, it would be safer to use something which is relatively more vapour open on the cold side of the cavity.

e.g.

PIR foam µ = 60
EPS µ = 60
mineral wool µ = 1

Bricks and blocks have µ between about 10 and 150

You raise some interesting points and I had not thought about it to that degree. However having considered it a bit more, I think the issue is probably still not a great one. The µ value needs to be multiplied by the thickness of the material to work out how vapour permeable it will be I believe? I have used 500 gauge polythene protection sheet which I think is only 0.125mm thick. The PU foam is 300mm thick, so the PU foam should still have greater resistance to vapour than the thin polythene sheet?

Well, that's reasonably thin polythene, but on the other hand water vapour diffusion rate in PU is higher at higher temperatures, meaning that it'll pass into the region near the outer edge relatively quicker.

You might find that it's OK everywhere except on North facing walls (due to lack of summer drying), or you might find that it's fine everywhere. I couldn't say one way or the other off the top of my head...

I think I'd probably advise looking at it in Wufi a bit - and maybe using mineral wool batt on the outer edge for any further walls to be on the safe side.

A less analytical approach might be to stick one of these https://www.toolstation.com/shop/p56239 on the end of long strip of ply and decreasing the vapour resistance of the polythene layer.

I've got some Teplo ties left over for a 300mm cavity for sale if anyone wants any.
Can be cut down for smaller cavity easily.