Yes thanks Jonti,

Questions remain though:

To what extent does a cavity contribute to the spread of fire?

And how common/uncommon is a cavity in EWI rendered systems?

Yes, but we are yet to see any EWI render systems which have a cavity other than on timber frame (which I would suggest is a rare application)

So how relevant is the fire risk for retrofit to solid wall insulation to dwellings? (which is the huge majority of the market)

Yep they do, but I was asking about rendered systems

Most of Weber solutions show insulation direct on wall without any cavity , but the remodelling facade solution shows a cavity behind a new external sheathing and insulation

http://www.netweber.co.uk/external-wall-insulation-systems/weber-systems/problem-solutions/new-build/remodelling-facades.html#tab1

Posted By: jamesingramMost of Weber solutions show insulation direct on wall without any cavity , but the remodelling facade solution shows a cavity behind a new external sheathing and insulation

http://www.netweber.co.uk/external-wall-insulation-systems/weber-systems/problem-solutions/new-build/remodelling-facades.html#tab1" rel="nofollow" >http://www.netweber.co.uk/external-wall-insulation-systems/weber-systems/problem-solutions/new-build/remodelling-facades.html#tab1

Well found James. That seems a crazy system though - having a cavity outboard of a masonry wall but inboard of the insulation. Any gaps would lead to huge ventilation losses surely.

The other claim is a real concern though - especially for high rise buildings and suchlike.

Probably a non-issue for housing though- if the fire is bad enough for that to happen then the inside is probably already toast

Yeah maybe. I guess its a little subjective.

I have a student who is currently looking at Part P. ie, To what extent has Part P has reduced the incidence of death or injury resulting from fires. One of his literary sources is to research fire safety officers statistics.

I would imagine statistics of fire spread through insulation are pretty low - though who knows?

The other thing these fires seem to have in common is that the insulation type. Maybe PIR is less of a risk?

The Part P topic is his choice as is for a Dissertation. I think he shares your view and is investigating this in the context of whether Part P should be more onerous to comply with in the proposed revision.

Yes I read that - Not surprising, around half the cost by R- value here as well isn't it?

Easier to cut, cleaner job, non itch, no apparent airbourn nasties etc.

I have not been able to watch the German piece again as it only runs at 2 to 3 seconds at a time (thats superfast rural broadband for you) but in the link to the written article it seems that although it is not so easy to get Polystyrene to burn (it needs a prolonged heat source) once it is burning it acts like an accelerant and is proving difficult to put out.

There was no mention of the effect of the cavity but it said polystyrene was so popular due to it being so cheap but that rockwool would be a better alternative from a fire risk point of view. The biggest concern seemed to be that with many buildings being higher than 3 stories any fire above this level would be out of the range of the fire brigades capabilities to tackle it. In the original TV piece concern was also raised that if sufficient heat was generated the material would burn meaning that were there many buildings in an area using this material then fire could jump from one building to the next very rapidly.

Jonti

cheers Jonti
I've email the link to the full program to a friend over in Germany , hopefully he might take a look and offer his thoughts. http://www.youtube.com/watch?v=MKeRe7FA4Gs

Thanks Nick.

Ed, It's a work in progress, I think it may well evolve or even center around shock hazards.

As ever the results will be reliant upon the student concerned willingness to share - usually not a problem

Sorry to jump into this late, but I believe that it's common to use intumescent strips closing the cavity on vented EWI systems, where flammable insulation is used behind a render board (e.g. EPS or to a lesser extent PIR) - particularly on high-rise buildings...

e.g.

http://www.tenmat.com/Content/Ventilated%20Fire%20Barriers

http://www.cfpltd.co.uk/ventilated-fire-barriers.html

etc.

As has already been said, non-flammable EWI materials are available...

Tim.

Fire Safety Briefing -EPS insulation
http://www.eps.co.uk/pdfs/fire_booklet.pdf

fostertom posted this on the AECB forum, I thought it would be of use to post here.
It from the british plastic federation trade body , EPS group,
"CONCLUSION
Fire safety is one of the essential requirements when designing a building.
It cannot be compromised. The role of insulation in respect to fire safety is
often over-rated. This document shows that it is perfectly possible and,
indeed, desirable to design a building using EPS as insulation material and
fulfil all insulation requirements, including fire safety."

Ta James. Other http://www.eps.co.uk propaganda sheets are v interesting too.