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Fire proof external insulation?


Lehaut
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A façade caught fire here in Nantes last night.  There has been a massive increase in external insulation around here recently.  Mostly large blocks of PSE (?) fixed to the outside of buildings then covered in an coating (enduit).  (90% of flats use this).

From what I have found, there does not appear to be a incombustible version of PSE:

https://isolation.ooreka.fr/astuce/voir/95850/polystyrene-expanse-pse-et-resistance-au-feu

There may well be better versed people on the forum who know better.  I would welcome their input.

Reason being.  Our current residence is partly insulated with rockwool at our level.   1 Jan 2025 introduces an obligatory energy audit for residences which could lead to some major works including external insulation. Other blocks in the area have seen bills of €30,000 per flat to get the resulting work done!

L’isolation n’a pas résisté aux flammes.

 

Nantes. La façade de l’immeuble prend feu, 46 locataires évacués.html

Edited by Lehaut
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Good afternoon Lehaut,

I've been a long time away from the forum, having mostly sold up in 2015. I was unfortunate to be caught up in the aftermath of the Grenfell Tower tragedy through being a leaseholder (and for my sins, the founder and chairman of the building's residents' right-to-manage company) in a block that had the same combination of insulation and rain screen materials as was used on Grenfell.

I had to spend a lot of time researching the subject and as a result we ended up with a pretty good solution, and even more fortunately we were able to get it funded by the UK Govt Building Safety programme. At the outset, we were being offered materials that had various claims made about them in terms of their resistance to the spread of fire. Once you took a long hard look at them, however, most materials which claimed to be "modified" plastics of any sort or treated with a "fire retardant" chemical, were ultimately still capable of spreading a fire and generating noxious fumes.

If you want non-flammable materials to be used, then you are basically restricted to Rockwool-type insulation (though there may now be suitable ceramic/cement foam products that you can use) and metal sheet or ceramic panel rain screen. To have a Euroclass A1-rated system, we couldn't even have painted metal sheets for the rainscreen.

Although the cost of the materials is significant, labour made up a big part of our costs, with the scaffolding being the third major component. Overall, the difference in costs between having an Euroclass A2-rated system (where people may still ask questions about combustibility) and an A1-rated system was quite small.

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I notice that the facade is of the building in Nantes is covered in wood, which to me  is quite obviously inflammable.

Our nephew was in York university until recently. I looked on Google Street View at the residential buildings at his address on campus and was surprised to see they are clad in wood.

The latest timber clad buildings were finished in 2022, five years after Grenfell. https://www.dezeen.com/2022/05/18/tateco-supertexture-creative-centre-york-st-john-university/

Does someone think that timber is less inflammable than plastic materials?

 

 

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2 hours ago, ssomon said:

I notice that the facade is of the building in Nantes is covered in wood, which to me  is quite obviously inflammable.

Our nephew was in York university until recently. I looked on Google Street View at the residential buildings at his address on campus and was surprised to see they are clad in wood.

The latest timber clad buildings were finished in 2022, five years after Grenfell. https://www.dezeen.com/2022/05/18/tateco-supertexture-creative-centre-york-st-john-university/

Does someone think that timber is less inflammable than plastic materials?

 

 

I had quite a few discussions with "the men from the ministry" and our very expensive Chartered Fire Engineer about the regulations that implied that below 18m in height, very flammable materials suddenly became not worth worrying about.

Wood is an interesting one because (apparently) thick pieces of dense wood tend to char and so are considered less combustible. The stuff that some appear to have been using as cladding looks to be neither thick nor dense ... 

Euroclass B still means that it will have some combustibility. However, you can apparently clad your own house in wood, and you will see new-build terraces of wood-clad houses, on the basis that the risk is low from what I understand.

Non-residential buildings are a completely different matter, and all bets are off. If a building is commercial or a day-patient hospital etc, then because it is not residential accommodation and in particular no-one sleeps there overnight, my understanding is that combustible cladding can still be used. I have become an expert in spotting very combustible High-Pressure Laminate which is to be found on a surprising number of buildings. 

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Pickles, thank you  for your reply.  All the current external insulation installations within a 1km radius of us are all thick blocks of expanded plastic, rendered and protected at the base by metal.  I will have to acquire a piece and try to set it alight. 

I also believe all these forms of insulation have a "life" too.  Though I will not be around for this building's replacement if it is actually done!

As for wood, I was interested to read this piece in the Guardian some time ago, the claims are quite interesting regarding its fire resistance;

https://www.theguardian.com/artanddesign/2023/jan/30/caress-lift-eco-office-block-miracle-wood-timber-black-white

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On 06/05/2023 at 08:11, Lehaut said:

Pickles, thank you  for your reply.  All the current external insulation installations within a 1km radius of us are all thick blocks of expanded plastic, rendered and protected at the base by metal.  I will have to acquire a piece and try to set it alight. 

This type of system is very dependent for its fire safety on the integrity of the render and the proper fitment of protective shields of non-combustible material, especially around door and window openings and any protrusions. The expanded plastic may be "treated" to reduce its flammability and promote charring, so that it will tend not to promote a fire (and may be difficult to light), but if subjected to a fierce source (eg flames coming out of a fully-developed fire through the windows), from what I was able to see, they will still burn and produce really nasty toxic gases. The temperatures produced by a fully-developed fire in an apartment make "man holding blowtorch to insulation" look like a kitchen match in comparison. The inspections that were carried out on UK buildings after Grenfell revealed many examples of shoddy workmanship, where gaps were left between metal covers and the parts that they were supposed to be fixed to, and gaps filled with combustible material, missing fire-stops, wood frames used as supports for the various elements, etc etc. Once this type of system has been fitted, even well fitted, then of course it has to be properly maintained, and any modifications (eg when people fit external shutters or new windows frames, or ventilation flues etc) need to be properly installed to ensure that they don't provide a path for air and fire to get into the insulation. These subsequent modifications are frequently carried out by people who have absolutely no idea what the implications of their works could be. This is why we went for a system that had no combustible elements in it as it reduces/removes the risk of the effects of a maintenance or installation oversight or subsequent damage.

Incidentally the rain screen that had been originally fitted to our building would withstand a blowtorch played on its aluminium surface for quite a while (we know because when we removed samples for testing by BRE, we had some material left over and our maintenance guys had a blowtorch, so inevitably we played with it), but as soon as the blowtorch touched an exposed edge (where the plastic core between the aluminium outer sheets was exposed), the sheet sample caught fire in a very impressive manner. Don't do this at home! 

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One thing I would like to know about arises from a comment I heard by a Grenfell resident who escaped from a flat some way up the building.

He said that the first he knew about the fire was when smoke seemed to start coming out of the wall below and around the window(s).

This suggested to me that perhaps, when the insulation was installed, this caused the windows to be recessed into the walls, by the thickness of the insulation and cladding, restricting the view, which led me to think that maybe the window frames were moved outwards so they were again flush with the walls.

This would mean that the "exterior" insulation would now be inside the building around the windows.

Also, the windows would have to be fixed in their new positions, and having seen how new windows in our son's house in England were installed, I just wondered if they could have been held in place with the ubiquitous polyurethane foam.

Doesn't bear thinking about, and it's all disappeared now.

 

 

 

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11 hours ago, ssomon said:

One thing I would like to know about arises from a comment I heard by a Grenfell resident who escaped from a flat some way up the building.

He said that the first he knew about the fire was when smoke seemed to start coming out of the wall below and around the window(s).

This suggested to me that perhaps, when the insulation was installed, this caused the windows to be recessed into the walls, by the thickness of the insulation and cladding, restricting the view, which led me to think that maybe the window frames were moved outwards so they were again flush with the walls.

This would mean that the "exterior" insulation would now be inside the building around the windows.

Also, the windows would have to be fixed in their new positions, and having seen how new windows in our son's house in England were installed, I just wondered if they could have been held in place with the ubiquitous polyurethane foam.

Doesn't bear thinking about, and it's all disappeared now.

From what I think I recall, I don't think that they moved the window frames outwards. However, I seem to recall that they were badly fitted, as you imply, with liberal use of polyurethane foam. There were also holes between flats where upgrades to heating systems etc had essentially destroyed the fire compartmentation that the "stay put" strategy relied on.

The other issue that you touched on was about the lack of warning. We had lots of discussions about this. With a "stay-put" strategy, you do not have a linked fire alarm system that can be heard inside the individual flats: there may be an alarm system in the common parts but it is not intended to be heard inside the flats. The reason for this is that you are supposed to be safe in your fire-compartmentalised flats and you do not want the fire brigade coming up the single set of stairs to be hampered by residents getting out. That's great as an idea, but I felt quite uneasy about this in our building.

Most incidents are the result of a "Swiss cheese" effect: normally all the holes, or failings, don't interact but occasionally the holes line up and create a disaster.

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