It is difficult to write about the Grenfell Tower disaster in London, as the number of fatalities continues to rise. But it is going to be a turning point in how we think about building design. The major issue with the building appears to be the choice of exterior cladding used in the retrofit, which the Daily Mail claims was chosen to meet “green targets.” No doubt we will be hearing a lot more about this, but it really isn’t fair or true. There were a) other reasons for recladding and b) other choices that could be made.
Daily Mail/Screen capture
A) Why was it re-clad in the first place?
Grenfell Tower was built as Council Housing in 1974 and was in desperate need of a retrofit by 2012. It plagued with problems, including leaking heat in the winter, but more significantly, overheating in the summer. Leo Hickman at Carbon Brief takes a close look at the Daily Mail’s claims and addresses them in his Factcheck: Grenfell Tower fire and the Daily Mail’s ‘green targets’ claim.
The poor insulation levels and air tightness of both the walls and the windows at Grenfell Tower result in excessive heat loss during the winter months. Addressing this issue is the primary driver behind the refurbishment. Due to valid safely concerns the windows at Grenfell Towers are restricted to open no more than 100 mm. [four inches, and this is common in North America too] This restriction causes chronic overheating in the summer months. It is essential that the renovation works do not make the overheating problems any worse and where possible we will strive to reduce overheating in line with current guidelines.
2012 Planning Application/Screen capture
The Daily Mail editorializes:
The more we learn of this tragedy, the more it appears that the blame lies not with money but staggering incompetence and misguided climate change targets…Was it, as official documents suggest, an attempt to slash greenhouse gas emissions?”
But as Leo Hickman notes, there are many reasons for recladding.
So, to conclude, “green targets” are far from being the “key” driving force behind refurbishing public housing stock. Reducing fuel poverty as well as improving the personal comfort and health of residents are also key motivations, as the planning documents cited above clearly state.
B) what about the building design? Why were people told to stay in their units?
Planning submission building plan/Public Domain
There are lots of issues to be discussed, going back to first principles. In Europe, they often take a different approach to fire safety than North Americans are used to, where there are two stairs separated by a pressurized corridor so that people can get out on their own in a hurry. As noted in the review of an earlier fire in Lakanal House:
High-rise fire protection, particularly in blocks such as Lakanal House, which have only one staircase, is based around the principle of compartmentalisation – the idea that fire and smoke will be contained within an individual flat or corridor long enough for residents elsewhere to escape.
It is assumed that in a fire in one unit, people in other units can safely stay put until the fire department comes and gets them. It usually works. As Mark Coles, head of Technical Regulations at the Institution of Engineering and Technology explains in the Engineer:
In a multi-occupancy high-rise building such as this, any fire which starts should be sufficiently retained for a period of time within that residential dwelling,” he added. “The intent at the design stage of this building was such that the staircases were not intended to be used as a mass escape route. The advice given to residents was that, in the event of a fire, the occupants should remain in their properties. The speed at which this fire spread would suggest that there has been a serious failure in the design and installation techniques employed.
B) what about the cladding choice?
From Planning report/Public Domain
In this case, the fire came from the outside. The building was clad in Reynobond PE a sandwich of thin aluminum with polyethylene in between. This is similar to Alucobond, and both are very common cladding materials. I have used them myself in the last building I designed as an architect. It acts as a rain screen; there is then a two inch cavity and attached to the building, six inches of Celotex RS5000 polyisocyanurate rigid insulation.
According to The Construction Index, alternatives were available. “Reynobond PE is not as fire retardant as the alternative Reynobond FR, which has a mineral core, but it is lighter and so easier to install.”
What appears to have happened is that the Reynobond’s polyethylene core caught fire and the stack effect in the two inch gap made it spread almost instantly. Apparently it got hot enough that the supposedly flame-retardant polyiso charred as well, putting out tons of smoke, possibly contributing cyanide and other toxic gases. The vinyl framed windows also melted, letting the toxic fumes into the suites very quickly.
There are many messages that can be taken from this.
1. this is not an indictment of green building.
That is just the Daily Mail taking advantage of a disaster to advance their anti-green agenda. The building wasn’t re-clad to meet green targets (they didn’t exist in 2012) and there were many alternative methods.
2 It is an indictment of plastics and foams in construction.
We have shown so many fires like this from the middle east. They happened in Melbourne and in London. There are rock wool and fiberglas alternatives that work perfectly well. There was no need to clad the building in flammable plastic.
3 Every building should be sprinklered.
They knew it here, but it was expensive and disruptive and it wasn’t legally required. It is obvious that it should be now.
4. Don’t let this become an indictment of wood construction.
Worth noting many of same experts who warned about risks also say wood-frame blocks of flats – v common now – are big potential worry.
— Peter Walker (@peterwalker99) June 15, 2017
People are already circling on this. Heavy timber and cross laminated timber do not burn like plastics; they char and take hours, not minutes to catch. The buildings made of it are usually sprinklered. It is not the same thing, but I guarantee that the concrete and masonry people are already composing their advertisements.
5 I’m going to stop complaining about North American fire safety design protocols.
Literally for decades I have complained about the North American way of designing apartment buildings, with two big pressurized stairs and a corridor in between, all designed to be big enough to evacuate the building in minutes. The Europeans had so much more design flexibility with their single stairs and units opening up onto landings.
But in retrospect the North American approach of Get out fast and get out now appears to be a whole lot better than the European one of Stay put and we will rescue you. As an architect, reading the story about the young Italian couple calling home while they wait to die was like a stab through the heart. I will never complain about the two exit requirement again.
© Getty Images
It is so unfortunate that it takes such a horrible tragedy to make architects and builders and code writers and building authorities get off their collective asses and do something, but this disaster is going to cause massive change and disruption in the industry worldwide.