Polystyrene Insulation

Polystyrene - fire safety - toxic fumes, bad news. Polystyrene - contact with pvc insulated wiring - hardening and cracking of insulation.

I think if your floors ablaze, the polystyrene fumes are the least of your worries;-)

good point about the PVC tho

snipped-for-privacy@gglz.com wrote:

Thank you for the replies, not sure whether to post at top or bottom. However, had the idea that the foil would delay spread of flames and flames would burn away from it anyway. Flooring is screwed down so not a big job to dismantle. Could have sworn Kingspan was Polystyrene with added foil, and is recommended for under floor. Also I notice Wickes sell Polystyrene for the same purpose. Is consulting the Local Authority Building Inspector FREE.??

rich snipped-for-privacy@hotmail.com wrote:

Kingspan is polyurethane

Most Kingspan/Celotex boards are polyurethane which is a much better insulator - 25mm PU is as good as or better than 40mm EPS

If it is flooring grade insulation then chances are it is treated with a flame retardent anyway. So it will melt if you heat it enough, but ought not add to the spread of flames. So if you keepo it out of contact with any PVC it ought to be ok.

Note that kingspan etc are not the same - they are Polyisocyanurate (PIR) foam.

No. It's foam with added foil, and twice the price of polystyrene. Presumably it smells sweeter when ablaze.

, and is recommended for

================================ I did this same job about three years ago except that I used just the polystyrene without foil. I asked my local BCO about suitability and he said there were no problems with using polystyrene in this way.

I was aware from posts elsewhere that PVC wiring and polystyrene was a bad mix so I made sure that the wiring runs were kept separate from the polystyrene. As far as fire risk is concerned I don't think I've ever heard of a fire starting under a suspended floor so I think the risk must be quite minimal.

Cic.

It doesn't burn _very_ well, but it does catch fire. So I found out when using some of it to protect the walls whilst chopping some 1/4" plate with an angle grinder in-situ in the lounge.

:¬)

One of its combusion products is cyanide, although I doubt you would be able to smell the almonds amongst the other things. You can smell it when you cut the sheets with a knife (it's probably a more complex cyanide-based molecule in this case).

Combusion products of polystyrene are pretty nasty too because it does a bad job of burning all the products, and you end up with significant amounts of unburned styrene, carbon monoxide, benzene, toluene, etc coming off. If it's old polystyrene, you also get combustion products from the incomplete burning of the CFC used to expand it, which can include hydrogen fluoride.

On 21 Dec 2006 04:06:05 -0800, a particular chimpanzee named "ken70" randomly hit the keyboard and produced:

Thank you Hugo...lots to read....think I'm covered but checking with County Hall after the holiday. If not O.K'd cheapest way out would to paint on some flame retardent. Got the original info from a 'Which' DIY book (published 1999), should have come here first. :-)

Hugo Nebula wrote: