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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Chris Houston on July 21, 2005, 06:51:45 PM
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Modern buildings are increasing incorporating combustible materials. Timber cladding, composite panels, use of expanded polystyrene external insulation, plastic flexible roofs and other plastic are being used more and more frequently.
I'd be interested to hear the thoughts of fire fighters about this, especially external insulation finish systems, where it can be difficult to differentiate between combustible and non combustible inuslation by a visual inspection alone.
I'd also be interested to see what other trends are being observed.
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Chris,
A newly constructed, partially occupied residential apartment block in central manchester, callef 'The Edge' recently burned well when the external cladding caught fire. Fire extended up several floors, I think. Combustible inner core to the cladding. Looks like enforcement is restricted to writing letters to Building Control and AI's exhorting them to consider carefully the potential for floor to floor spread externally.
I do sometimes think that developers, architects, et al push things too far while hoping that statisically they will get away with it.
Residents' group, understandably, raising one or two concerns.
I am not sure whether there will be any action on the back of this fire....a number of other developments are using the same systems.
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James
Building Control can only enforce the minimum standards of the building regulations and until the guidance of ADB is altered this type of construction will continue to be commonly used (cheap and quick).
Luckily the draft ADB contains revised guidance in clause 11.7 'In a building with a storey 18m or more above ground level, insulation material used in cavities in the external wall construction should be of limited combustibility' so we may be able to control taller buildings in the future.
Also clause 7.23 of the draft says 'At the junction of a compartment floor with an external wall that has no fire resistance (such as a curtain wall) the external wall should be restrained at floor level to reduce the movement of the wall away from the floor when exposed to fire.' Again this is useful guidance.
Lets hope this makes the final approved document so that we can enforce a sensible standard in the future.
Dave.
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James,
Have you any more info on this, perhaps a link?
"Limited combustibility"? Why not non-combustible - there's a crazy idea. I was in Estonia recently, looking round Tallin's heritage museum I read that a law was passed in 1700 to ensure that houses were built of stone to prevent fire spread. Perhaps we have something to learn.
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Sorry Chris,
I think there is still a possibility of a court case...you know what Manchester's like.
The fire travelled up the outside in about ten minutes and did damage in some of the floors, (ie would have broken into several storeys if they had been finished and occupied.
You could try a formal letter from you employers to ask for the results of the investigation. I think it would be reasonable for a major building insurer to be interested in this sort of thing!
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Chris
Did you know that Mineral wool insultation is not a non-combustible material.
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Chris
Did you know that Mineral wool insultation is not a non-combustible material.
B,
No I didn't. Would you care to clarify this point?
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Most mineral wool insulation products use a polymer binder to hold them together.
This means that they dont pass the non-combustibility test.
If we resticted buildings to using only non-combustible materials we would be restricting lots of products that don't really cause a problem, hence materials of limited combustibility.
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Well done, Wee B, I am always reminding people about this, but actually plasterboard is a better example.
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I am amazed that such competent persons are debating this subject. I remember being told at one of the early courses at the centre of excellence that all things will burn in the right circumstances. Iron and steel in oxygen etc. Perhaps I am missing something Colin?
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Brian, I don't understand why you are amazed.
Perhaps I should have been more specific. Non combustible in air is what I meant.
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Most mineral wool insulation products use a polymer binder to hold them together.
This means that they dont pass the non-combustibility test.
If we resticted buildings to using only non-combustible materials we would be restricting lots of products that don't really cause a problem, hence materials of limited combustibility.
Which non combustibility test does it not pass?
This is news to me, I had always considered mineral wool to be entirly non combustible (in air, in normal building fire situations.)
Please tell me more.
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I have just checked out the webpage a manufacturer of mineral wool insulation. I quote:
"All unfaced, aluminium foil faced and glass tissue faced ........ products produced in the UK are non-combustible and will achieve a reaction to fire classification of A1."
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Chris,
Replying to your original post:
Check out Appendix 'F' of ADB - then that refers you to the International Association of Cold Storage Contractors (IACSC) Panel Labelling Scheme. However, few brigades know much about this I'm afraid.
In my experience, Polyisoyanurate foam filled panels (PIR) have performed very well - much better than I'd have expected (2 supermarket fires I attended as o.i.c) and where they did not burn, however, other materials around them certainly did.
My research reveals that the very large lossess suffered in the 'food industry' is mainly due to polystyrene panels (EPS or XPS). These are popular for cold stores or chillers - much more so than mineral wool (MRF). The food industry does not tend to favor MRF.
A very good source of information is International Fire Consultants at Princess Risborough.
But my final point is that: if soffits and fascia boards were mineral wool or similar - we would cut down on an awful lot of serious fires where material is ignited externally, but which then spread inside roofs etc.
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Chris - your right - they seem to have got an A1 for all thier products now. But products from other manufacturers and products that use glass fibres instead of rock fibre may not quite hit the target.
The point I was trying to make (not very well) is that Non-combustible (Euroclass A1) is a pretty tough classification and many perfectly safe products would be discriminated aginst.
I've seen mineral fibre batts burning so I know it happens (no it wasn't in an oxygen rich atmosphere)
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Yes OK chaps I do know that the subject is about materials burning in air. That was just an extreme example. After all air is 1/5th O2. On a serious note I have not seen a fire barrier in a roof that does not have gaps or holes, some you can shake hands through and some that you could even climb through. I do not think that the contractors that run cables or pipes through them understand the significance of repairing them afterwards.
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Brian,
You are so right re fire barriers! A subject that deserves far more attention than it gets by either building control officers or fire officers - or others. I'm suggesting to the ABE that we run a course on this topic so any suggestions/encouragement would be valued.
Regards
Ian
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I have been informed that Insurance companies are now asking for higher premiums for building that are using combustible insulation material such as polystyrene in walls. These cases were for new buildings and althought I have not been able to determine what exactly the characteristics of the polystyrene was I would be interested to know if this is a regular occurance?.
The fire risk assessments I suspect will not have considerd the risk of fire spread within cavity walls, as with new build they would presumibly complied with Part B.
Any observations would be welcome.
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Polystyrene is a thermoplastic, so when heated melts and runs (and to some extent degrades back to its building blocks of styrene monomer, an HFL).
End result is that a small contents fire can get very rapidly out of control, as demonstrated by the near-endless list of food factories that have burnt uncontrollably.
Other factors involved are that the panels are mainly used internally, with simple butt joints, which have no mechanical integrity. Compare these with the complex joints used for external cladding panels.
Insurers are generally quite happy with polyisocyanurate panels approved under LPS1181. Much better performance! For convenience, we tend to regard these panels as being non-combustible (OK, not technically true, but this is only one of many issues our underwriters have to consider, and simplification is necessary).
But given large enough volume/fire load, the choice of panel becomes less significant, and sprinklers will be necessary.
Fire Risk assessments? Yet to see one which takes polystyrene into account, but I live in hope......... Some dreadful reports from various other countries of deaths related to the stuff.
And in relation to Ian Gough's comments above, I can but agree! The standard of so-called fire-stopping insurers see is generally dreadful: so we ask for 3PC to LPS 1132 whenever we get the chance.
Plenty of perfectly good uses for polystyrene, but composite panels are not on that list!
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Some insurers will charge more, some will simply refuse to insure buildings using expanded polystyrene as insulation either in a panel or as part of a built up system.
LPS 1181 has two grades A and B, only a Grade A panel has a determined amount of fire resistance.
Going back to my original post, what do fire fighters think of these systems, I didn't want a sandwich panel debate, that's been done enough, it's the other odd things that I am interested in views on.
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Modern buildings are increasing incorporating combustible materials. Timber cladding, composite panels, use of expanded polystyrene external insulation, plastic flexible roofs and other plastic are being used more and more frequently.
I'd be interested to hear the thoughts of fire fighters about this, especially external insulation finish systems, where it can be difficult to differentiate between combustible and non combustible inuslation by a visual inspection alone.
I'd also be interested to see what other trends are being observed.
I'm no fire-fighter but bearing in mind that the setback distance from the boundary is usually based on the sizes of unprotected openings. if combustible material are used, the amount of "unprotected openings" is increased and will pose a thread to adjacent properties.
Doug Drysale has a section on alternate means of calculating "unprotected openings" using configuration factor. Some of the international codes like NFPA, International Fire Engineering Guidelines, etc specify the amount of heat generated from such opening based on occupancies/ etc. An industrial building will have 168kW/m2 as compared to office occupancies of 84 kW/m2.
Margaret law has conducted research on cellulosic material (timber) and suggested that the heat intensity of < 12.5kW/m2 at the boundary.
hth