Flame retardent "celotext" - is it?

[Tim W]

A while back, something I'd not heard of came up hear: namely the fact that not all "celotex" PIR foams may be fire retardant.

Being concerned that I have 15 sheets in the shed which I wish to deploy in the house, I tried a test today.

I cut a 15mm x 15mm ish 50mm long cuboid off, minus foil.

I set to it with a lighter then a blowtorch.

The lighter would cause a flame to briefly lick over the surface which them went out after 2-3 seconds. Surface became black. Seemed impossible to relight the black bits.

I tried it with a blowtorch - very similar: flame licked around a limited area (I was holding the other end with bare fingers at this point). Flame died. I repeated this all round one end until all surfaces were black. Small amounts of foul smoke were emitted.

After that, directing a blowtorch at it caused the black layer to glow red hot but the piece did not seem to want to relight.

The piece has shrunk at that end to around 10x10mm wide.

Does this sound like it's the flame retardant type? It seems so but I have no other types to test, so I don't know what non retardant PIR would do. Also this was a very small test sample - I don't know what happens if it was exposed to a "real" house fire.

Cheers

Tim

[Andrew Gabriel]

Yes - it won't sustain a flame.

Burns more like a piece of expanded polystyrene (not quite as bad, but very much different from your example).

It will still give off all the same toxins if there's some other fuel source roasting it, but it won't fuel a fire itself. Normally, it's not exposed (at least in the living quarters of the house).

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Tim W saying something like:

Even if it is the flame-retardent type I wouldn't want to be exposed to a naked wall of it which was being heated by a house fire and giving off gobbets of smoke iyswim. Securely sealed in by plasterboard it's safe enough, for at least the minimum amount of time.

[The Natural Philosopher]

Its all like that IME.

CeloTex BTW

[Tim W]

Grimly Curmudgeon wibbled on Thursday 07 January 2010 23:12

Thank you Grimly/Andrew/TNP. That sounds good news.

It's BallyTherm BTW.

So the next question is:

Where it's in loft spaces (fitted up inbetween and under the roof rafters) is it necessary to cover it?

Those spaces are a cupboard door away from a habitable area. Obviously the bits in the habitable area will be PB'd over. But I'm not totally relishing applying PB inside roof voids - and it's not totally practical either in all areas due to access (pipes etc in the way) though I *could* cover perhaps

80% of it. It's down at the last 2 foot towards the top of the wall leafs that becomes difficult.

Would hardboard be better than nothing there where possible (it's thinner)? Added complications would be that while I expect to go for 50mm between the rafters and 50mm over, again down near the wall tops, I might have to step down to zero or maybe 25mm if I'm lucky over the rafters - and steps in the thickness don't help with applying sheet materials as you can imagine!

Bearing in mind it's foil covered - I haven't tried burning it through the foil yet...

Cheers

Tim

[The Natural Philosopher]

Nope.

use foil tape to seal it to rafters

Dont worry. If it starts to burn, the house is already well alight.

[John Rumm]

no...

Lots of aggro for not much reward really. Not to mention the extra weight, cost, and presence of hygroscopic gypsum in a cold environment.

Worse I would have thought since it is directly combustible.

There is a secondary fire risk issue when you have a whole space enclosed in the stuff on the inside of the main thermal mass of the building - that being that since it insulates so well, in a fire it dramatically reduces the time taken for the enclosed space to reach the spontaneous ignition temperature of anything in it. The PB in most domestic situations retards this process somewhat though.

[Bolted]

Lots of the cheaper mimics are PUR rather than PIR, and PUR burns more readily (much more readily in my limited experience of a sample of one type).

[Tim W]

Bolted wibbled on Friday 08 January 2010 13:46

Luckily, the Ballytherm tech brochure states: "Ballytherm Insulation is a foil-faced Polyisocyanurate (PIR) insulation board."

I don't think they're "cheap" (as in nasty) - more likely it's what came up on the seconds market...

Another good point though and something worth checking if intending to buy...

[Bolted]

I wasn't really aiming that at your panels rather TNP's comment that they are all like that (true wrt to real celotex, but not many imitations).

I only found out because the tosser of a builder who did the shell of our kitchen extension substituted a cheapo PUR instead of specced PIR and the tosser of an architect couldn't be bothered to argue with him (not his family being placed at increased risk). I checked to see if I was being overly precious and demonstrated the happily burning foam and pall of black smoke to architect who still lacked the balls to do anything about it.

[Tim W]

Tim W wibbled on Thursday 07 January 2010 22:57

Sorry folks - I should have read the tech brochure before (TBH I only just found it):

Quote:

"Fire

Ballytherm Insulation remains stable at temperatures up to 400ºC; at higher temperatures a protective char forms on the surface, slowing the spread of flame. Ballytherm insulation may be used safely behind non-flammable materials such as plasterboard. The products have been fully tested in accordance with B.S. 476: Part 7: 1997 Surface of Flame and have achieved a Class 1 Rating."

Doh.

But some general knowledge about these things was very useful - the next batch I get might not be Ballytherm.

[Tim W]

John Rumm wibbled on Thursday 07 January 2010 23:49

Makes sense.

Thinking it might be a idea to stick a couple of smoke alarms in the voids - being that's where all the cables run and interlink them with the rest of the smoke alarms.

Cheers

Tim

[Tim W]

Bolted wibbled on Friday 08 January 2010 16:14

Made me look though :)

Did you manage any come back against him, eg with BCO's help?

[Bolted]

No, it was just one battle in a constant war to get anything like the spec out of the builder, I gave up on that one and just made the ceiling as fireproof as I could when it came to fitting it out.

[John Rumm]

Not a bad idea, but remember they have a limited life span.