PIR foam seems an effective solution to insulating a house, but the information emerging from Grenfell indicates that it's not as fire resistant as I (for one) assumed to be the case and can give off significant amounts of toxic smoke.
It's also quite plausible that the current review of building regs will introduce controls on PIR use. I know we don't always worry too much about every details of the building regs, but they do provide sensible guidance for most things, can affect availability of materials and can sometimes lead to difficulties when selling a house.
I have assumed so far that, especially behind plasterboard, the risk was very low, especially when there are many tons of dry timber in the house and in any case fires are relatively rare events.
There don't seem to be any practical alternatives but is it time to question PIR use for domestic insulation upgrades?
this is where all the upgrading of dwellings got us....things made sense when the only requirement was the U value of walls to be 1 and roofs 0.6 ........and a timber frame house with fibreglass quilt in the 42 stud exceeded that requirement .... and warm deck unvented upside down flat roofs were the start of the use of materials like celotex.....
Indeed: I'd just like to make my place warmer and more energy efficient. Precise U-values aren't really all that important unless building control become involved, when it all becomes unrealistic in many situations for an old house. PIR looked like a good solution, but there's no point in having a warm house that you can't ever sell or is going to kill you
Every time I burn left-over building materials (most recently, any parts of my old kitchen actually made of real wood, which I cut up and put in the woodburner), I muse on how inflammable houses actually are. And why I change the smoke detector batteries every year, whether they "pip" or not. I think PIR boards are the least of our worries.
And why you should organise an emergency grab-bag containing passports and the like, which can be taken out in case of fire. Remembering that once a fire gets hold, most houses will go up and become dangerous in minutes.
I'd still reckon that if I'm not out by the time a fire gets through plasterboard and the PIR starts burning then I won't be getting out. Especially as - like many - I sleep above a lot of other stuff which may well be noxious - eg carpet underlay.
Fire resistance is the ability of a material to withstand a standard fire resistance test. Kingspan/Cellotex/polyisocyanurate foams are not significantly fire resistant. The blowing agent used to create PIR foam was originally CFC-11 which was replaced by HCFC-141b, neither were flammable. In turn HCFC-141b was replaced by pentane because of its lower global warming potential. Pentane is highly flammable.
Applying a flame to PIR board will create an instant burn (from the Pentane released) but it will not by itself support combustion, remove the flame and it will go out. Put it into a vertical wind tunnel with a fire at the bottom and surrounded by more flammable materials and it will help support combustion - which is what seems to have occurred at Grenfell. One significant product of combustion of PIR board is Hydrogen Cyanide, however the more normal products of combustion such as Carbon Monoxide are a greater risk as they do not require a raging fire to be produced and will kill you in your sleep before you realise there is a fire. Very few people die of burns in house fires, most are asphyxiated.
If used as internal retrofit insulation in a house PIR will be covered in plasterboard which is very fire resistant. If you lined your whole house internally with plasterboard lined Kingspan you will not have increased the risk from fire - other things burning within the house will have killed you long before the PIR foam degrading in the heat becomes a threat. PIR foam used as cavity wall insulation has no risk at all attached to it nor would it if used as part of external cladding on low rise properties.
I doubt if this will occur in properties other than high rise. It is the use of composite claddings on high rise buildings where attention will focus, not PIR board. Had the building been clad only in PIR board the fire would not have spread as it did. (But of course PIR board alone is not suitable as cladding).
Well - not so much if you deploy it in the attic... I did, but I did cover 90% in PB (can't get down into the eaves to do that bit). I did it to stop it getting dinged but peopel moving junk in the attic, but fire resistance was also in my mind, seeing as that's where most of the mains wiring and SELV PSUs are.
That roof on the Weybridge health Centre fire that trashed the building top floor in under half an hour was supposed to have been to the building regs. I do sometimes wonder who is in charge of deciding what a real world situation actually is! Brian
Yup concentrate on the things you can control - smoke alarms, emergency lighting, usable escape routes etc.
To an extent any insulation can make fire spread more rapid as it will often allow room temperatures to rise more quickly. However fire is a rare event and heat loss a common one, so you need to keep a perspective.
Polystyrene is far worse than kingspan and celotex - I know someone who's installing it on the sly - no no no.
Try burning a bit with a lighter and watch it spread!
I did this test with yellow foam and pinkgrip foam and discovered its very flammable, now i use the slightly more expensive firefoam for all my foamin g jobs insulating this old house - i buy a dozen cans at a time! Use it to stick kingspan seconds to walls and the gaps between them, and sticking Pl asterboard or OSB to the kingspan, no metal screws coldbridging coldness in from outside
I didn't know what blowing agent they used, you'd think that for FR it might be obvious to use CO2 rather than a flammable gas and it seems it
*is* obvious enough that some materials use it ...
Even if the difference between releasing a bit of pentane, and releasing some CO2 was minute in fire terms, you'd think they'd do it just for the ecobollox "carbon-negative" credentials ...
I assume you are not worried about the risks which follow from omitting the mechanical fixings which stop the plasterboard and insulation falling on you when you're trying to escape a fire (or on the fire service when they are trying to rescue you).
I assume you also quantified the loss from cold bridging you'd suffer with what are IIRC are the recommended 3 fixings per sheet. Last ones I saw being used month had a cross-section of 9mm2 so that's 27mm2 per sheet - or 0.0000094 of the area of a full board. And of course those fixing go into the underlying wall, not the outside.
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