Good observations from Mackenzie architects.
Had the exterior cladding been secured tight to the main charred insulation without the 'ventilation' gap we probably would not have seen the fire spread be so intense?
What past recommendations were given by organizations such as BRE to DCLG for the compiling of present building regulations, especially the introduction and need for ventilation behind cladding as ‘one shoe fits all’ for every exterior cladding product?
Of course ventilation is meant to deal with condensation and moisture retention and not act as a chimney for accelerating fire spread, this ventilation makes sense when used with hard exteriors such as inflammable unit tiles with little thermal insulating properties, but makes no sense at all with exterior weathering, insulating and slow breathable materials such as thatch which are designed to be one unit that regulate any moisture on the outer surface.
I’m not convinced the investigations will cover all aspects and dig deeper to find the culprits that gave bad advice in the first instance for this system (ventilation factor).
My thatching colleagues on the continent are gob smacked when I explain what is in or not in our building regulations that appear to be nearly two decades behind their understanding of Passivhaus and moisture problems!
I’ve only thatched the walls of one award winning commercial building (not high rise) in Norwich, it’s now doubtful this will be ever be repeated, but if asked to thatch a sky-scraper I would insist on no ventilation gap behind the thatch and would only consider a north wall with no windows or with barrier protected openings.
Signing out now, back to conservation work!
The question of how long the wall thatch will last has been asked of myself hundreds of times, all I can say is that walls thatched with wheat straw is a first on the Enterprise Centre and theoretically it should last 50 years plus because the vertical nature of the thatch never gets moist enough for serious fungal decay to get established. It's worth reading the research findings on thatching supply on Historic England's website to better understand how thatch works.