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Sledgehead

Amateur Prop Dev's Fave Conversion a Death Trap?

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The Grenfell Tower tragedy has led to a review of the building regulations.

An interview with an expert in the field of fire safety and buildings on the beeb yesterday concluded with him angrily asserting that the problems went beyond hi-rises. In particular he talked of timber frame constructions, where, during tests, fire could continue within the cavity for more than 24 hours. He said these findings were not incorporated in the building regs.

This got me thinking about the kind of insulation used in housing today. In particular I was interested in the rigid foam board insulation much loved by amateur property devs when converting lofts. Perhaps the best know of these is cellotex, a brand of polyisocyanurate or PIR. I was interested in whether this could pose the kind of threat alluded to by the expert.

The polyisocyanurate wiki site states:

Quote

PIR is at times stated to be fire retardant, or contain fire retardants, however these describe the results of "small scale tests" and "do not reflect [all] hazards under real fire conditions";

Sound familiar?

It then goes on to talk not only of flammability, but of the chemicals released during burning. The 'cyan' part of polyisocyanurate should give you a clue where this is going. As the wiki states:

 

Quote

PIR generally released a considerably higher level of toxic products than the other insulating materials studied (PIR > PUR > EPS > PHF; glass and stone wools also studied).[5] In particular, hydrogen cyanide is recognised as a significant contributor to the fire toxicity of PIR (and PUR) foams

And that rang a bell wrt Grenfell. Anyone else recall this:

Quote

... and so all that was left for me to do was join the dots:

 

Quote

Celotex RS5000 is a type of thermal insulation designed specifically for use in rainscreen cladding systems. It forms a layer of thermal insulation between the rainscreen cladding and the inner part of the wall construction. It is formed from a rigid polyisocyanurate foam core (PIR) and has a low-emissivity textured aluminium foil facing.

Celotex have confirmed that they supplied this insulation for the Grenfell Tower refurbishment.

 

In case you are wondering, PIR is stable to just 200 C

So how safe is this material? Are we facing another 'asbestos'? How many loft conversions are safe? And should you pay an extra penny for that extra space in a loft-converted house?

 

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How fire retardent is wood ? That's why its covered with plasterboard, joints are filled and a skin of plaster is applied. Most insulation is fitted between timbers .

The build regs aren't perfect but OK. Not enough inspections is the problem .

 

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Oak actually performs excellently under fire loads - what tends to happen is the first inch chars and then protects the core. If you add two inches to each dimension when specifying oak beams then you can be reasonably sure they'll remain structurally intact during and after a major fire.

Of course most trusses these days are softwood with structural designs engineered to  be as light as possible - a very different proposition.

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3 hours ago, chicker said:

How fire retardent is wood ? That's why its covered with plasterboard, joints are filled and a skin of plaster is applied. Most insulation is fitted between timbers .

The build regs aren't perfect but OK. Not enough inspections is the problem .

 

And the HCN? 

Polyisocyanurates by their very nature, contain concentrations of nitrogen simply not present in cellulose.

As for it being covered by plasterboard, you seem to forget:

1 ) This stuff is within the INTERIOR of the build;

2 ) The residents of Grenfell were separated from their celotex by the CONCRETE outer shell of the original block : the stuff was on the OUTSIDE!

And yet the HCN still got to 'em.

Edited by Sledgehead
mispelling of celotex

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Just now, Sledgehead said:

And the HCN? 

Polyisocyanurates by their very nature, contain concentrations of nitrogen simply not present in cellulose.

As for it being covered by plasterboard, you seem to forget:

1 ) This stuff is within the INTERIOR of the build;

2 ) The residents of Grenfell were separated from their cellotec by the CONCRETE outer shell of the original block : the stuff was on the OUTSIDE!

And yet the HCN still got to 'em.

Wasn't talking about Grenfell , my view was about loft conversions very different imho. Most lofts are 20ft from the ground  and have fire check walls between any adjoining property .

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1 hour ago, chicker said:

Wasn't talking about Grenfell , my view was about loft conversions very different imho. Most lofts are 20ft from the ground  and have fire check walls between any adjoining property .

I'm not talking about Grenfell either. I'm simply telling you that a full structural concrete wall was not sufficient to shield this material from the fire. True, temps will have been higher at Grenfell. But then again the fire protection afforded by a bit of plasterboard is much less than a structural concrete wall, and gases will be being produced inside the structure, rather than outside.

Besides, what you or I think is irrelevant. The evidence is already out there:

Hydrogen Cyanide: New Concerns for Firefighting and Medical Tactics - FireEngineering - 2009

Quote

Where Does Hydrogen Cyanide Come From?

Hydrogen cyanide is a by-product of the combustion of materials used in products used in everyday life (insulation, carpets, clothing, and synthetics).

...

the real offender is the combustion of manmade plastic and resins containing nitrogen, especially if the fire is hot and in an enclosed space. Common manmade materials that generate cyanide gas during combustion include nylon, polyurethane, melamine, and acrylonitrile. These materials are ubiquitous in building furnishings, vehicles, foam insulation, carpets, draperies, appliances, many plastics, and articles of clothing.

Sticking a few kilos of polyisocyanurate in your gaff doesn't seem like the ideal way to minimise these dangers.

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I've got loads of Kingspan in my extensions and loft conversion, put it in myself. There isn't really much choice to be able to meet building regs U values in a reasonable thickness.

I burned off a lot of building debris at the end of the project, the bits of Kingspan disintegrated quickly.

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I was just looking at the diy option for rigid insulation for loft. However,  the only option appears to be Kingspan after the thread date loads of celotex products have been suspended  ?  

 

Wickes used to stock Celotex but presume this was the 5000 line which the whole line seems currently suspended and to top it off a lamda calculation ‘issue’ was identified covering the 4000, and I guess the 5000 line(before it got suspended). So some of the 4000 Range becomes the 3000 Range ?

https://www.celotex.co.uk/celotex-statement-20th-november

4000 range and Crown-Bond and Crown Fix: all products manufactured in the XR4000 range, Crown-Bond and Crown-Fix ranges and GA4000 from 100mm and above will continue to be marketed as the 4000 range and Crown Range with a declared lambda of 0.022 W/mK.

2.     New 3000 range: all other current products from our TB4000, GA4000, PL4000 and CW4000 ranges manufactured after 15 December 2017 will be marketed from January as Celotex 3000 with a declared lambda of 0.023 W/mK.

Edited by Ash4781

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