This story originally ran in Engineering News-Record on June 28, 2017.
Following the deadly June 14 London Grenfell Tower fire that has killed at least 79 people, a nationwide investigation determined that dozens of U.K. high-rise buildings are potentially unsafe.
On their exteriors, all use an aluminum composite material (ACM) similar to the 24-story Grenfell Tower’s rain-screen cladding system. London’s metropolitan police department has signaled that it may file manslaughter charges in connection with the disaster. In the U.K., a corporation can be prosecuted for manslaughter.
New York City-based Arconic Inc., the maker of Reynobond (PE), a type of aluminum and polyethylene cladding used on the tower, has halted global sales of the product for high-rise buildings. “The loss of lives, injuries and destruction following the Grenfell Tower fire are devastating and our deepest condolences are with everyone in this tragedy,” said an Arconic statement, released on June 26. “We have offered our full support to the authorities as they conduct their investigation.”
The Grenfell inferno has increased doubts about U.K. building regulations on ACM cladding. Around 600 U.K. high-rises are estimated to have been retrofitted with ACM to improve their appearance and energy efficiency. Cladding samples are being rushed for combustibility tests, conducted by the building research organization BRE Group, Watford.
At press time, all 95 samples from 32 regions failed BRE’s tests, according to the Dept. for Communities and Local Government. A spokesman says that high failure rate is because the riskiest buildings were tested first. But David Metcalf, director of the Centre for Window and Cladding Technology, Bath, also believes regulatory confusion over ACM combustibility is being revealed.
“We’ve been working [in the U.S.] on test protocols for these composite cladding systems for the past 25 years,” said Robert Solomon, a building fire-protection division manager with the National Fire Protection Association, a nonprofit research organization committed to advancing fire safety.
NFPA Standard 285 evaluated fire propagation of cladding systems that contain combustible materials, which would include Grenfell Tower’s ACM rain screen. A 2014 case study of worldwide cladding fire events observed that “fire incidents … occurred in countries with poor (or no) regulatory control … or where construction has not been in accordance with regulatory controls.”
So far, only four U.K. buildings are being evacuated. London’s Camden Council began moving 650 families out of four 22-floor blocks at the Chalcots Estate after finding serious interior safety deficiencies, compounding the cladding risk.
Installed nine years ago, the buildings’ cladding is “not to the standard that we had commissioned,” said Georgia Gould, the council’s leader. “[We] will immediately begin preparing to remove it,” she adds.
Burning Questions
The U.K.’s worst peacetime fire in centuries was sparked by a faulty refrigerator in a fourth-floor apartment, according to the Metropolitan Police. Nearby flammable cladding ignited, spreading flames rapidly up and down the residential tower, investigators believe.
“This is an unprecedented situation, with a major fire that has affected all floors of this 24-story building, from the second floor up,” said Dany Cotton, London’s fire brigade commissioner. She has seen nothing like it in her 29-year career, she added.
The first of some 200 firefighters arrived within minutes of ignition, starting at around 1 a.m. on June 14, but the flames spread so quickly that the fire brigade had no time to reach many residents. In line with common high-rise safety practice, residents had been advised to stay put inside, awaiting rescue. Those that did so perished.
Almost immediately after the fire, government ministers were challenged for seemingly ignoring the All Party Parliamentary Fire Safety & Rescue Group’s advice to retrofit sprinklers in the U.K.’s estimated 4,000 older residential high-rise blocks. The advice followed a smaller fatal fire in 2009 at Lakanal House, a few kilometers away. Sprinklers are mandatory in new buildings.
Local authorities now are putting pressure on the government to fund sprinklers and other fire-suppressing measures nationwide, says John Clancy, the Labour leader of the Birmingham City Council. The city will invest $40 million in retrofitting its 213 apartment blocks, with or without government support, he says
While the Grenfell Tower’s lack of sprinklers allowed the fire to gain purchase, the rapid spread of flames revealed serious flaws in the recently fitted external cladding.
Built in 1974, the concrete-framed building with 120 homes is owned by the Royal Borough of Kensington and Chelsea and managed by the not-for-profit Kensington and Chelsea Tenant Management Organisation (KCTMO).
For the refurbishment, including cladding, KCTMO in early 2014 awarded a design-build contract to Rydon Maintenance Ltd., Forest Row, which completed the $12.6-million job last July. Rydon was also the contractor on the Chalcots Estate buildings. Studio E Architects, London, was the designer of the Grenfell work; it declines to comment.
To design and install the cladding, Rydon awarded a $3.3-million subcontract to Harley Facades Ltd., Crowborough. Celotex Ltd., a subsidiary of France’s Saint Gobain Group, Courbevoie, supplied RS5000 polyisocyanurate insulation, which was installed between the building and the ACM. Further, CEP Architectural Facades Ltd., Hastings, fabricated the rain-screen panels using the Reynobond (PE) composite system.
In the PE version, Arconic’s Reynobond is a thin composite of two coated aluminium sheets that sandwich a layer of polyethylene. There is also a costlier FR variant with a fire-retardant thermoplastic core. Arconic’s product literature advises that Reynobond PE should be used only up to 10 meters above ground.
NFPA’s Solomon says U.S. codes generally prohibit ACM systems that have combustible polyethylene material above 40 ft but allow fire-retardant systems or those containing non-combustible materials.
“We sold our products with the expectation that they would be used in compliance with the various and different local building codes and regulations,” said Arconic in a statement. European, U.K. and U.S. regulations permit ACM in high-rise buildings, “depending on the cladding system and overall building design,” it added.
CEP Managing Director John Cowley insists the ACM product is allowed “in both low-rise and high-rise structures” by current U.K. building regulations.
For conventional designs, U.K. building regulations set out minimum performance requirements. Details of how to comply are published in the so-called Approved Documents, which reference British standards and other technical guidance. In England, “any insulation product” on buildings taller than 18 m must be of “limited combustibility,” a term the documents define. But the wording is ambiguous, according to Metcalf. Official guidance “doesn’t explicitly say that the cladding should be of limited combustibility,” explains Metcalf. “Most people have interpreted it to mean it doesn’t need to be.”
Both the Celotex insulation from the Grenfell Tower and aluminium composite panels failed preliminary fire tests, according to police.
In recent years, manufacturers have supplied cladding systems and exterior insulation that feature materials that are lightweight, easily installed and less expensive than conventional systems.
Drawbacks
But there are several drawbacks, says Marc Weissbach, an expert on building enclosures and CEO of building-systems consultant Vidaris Inc. The notion that any high-rise building featuring an ACM system should be fully sprinklered is good for protecting the interior, “but the sprinklers are inside the building, and the fire is spreading—quickly—up the exterior,” he says. Also, sprinkler systems are seldom operable until construction is complete, which makes a building vulnerable to fire during construction, he notes. Such was the case in Beijing’s CCTV Tower fire in 2009 and The Address Downtown Dubai hotel fire in 2016.
The NFPA 285 standard specifies 15 minutes of protection from fire, “but is that enough time in a high-rise?” Weissbach asks. He favors the two-hour standard that was in place until 1968.
In addition, there is often a knowledge gap around proper system design and installation of the systems, Weissboch observes. If a building exterior is covered with combustible insulation material with a 2-in. air space before an outer ACM layer, there is a natural chimney effect that can spread a fire quickly once materials ignite.
Celotex and CEP question how the cladding was finally put together. The RS5000 insulation has been tested as “part of a particular rain-screen cladding system,” according to the maker. “Any changes to components … or construction methods used need to be considered by the relevant building designer.” Celotex has withdrawn its product for buildings taller than 18 m.
For CEP’s John Cowley, “the key question now is whether the overall design of the building’s complete exterior was properly tested and subsequently signed off by the relevant authorities, including the fire officer, the building compliance officer and architect before commencement of the project?”
Rydon claims to have met all required building and fire regulations. It handed over the work “when the completion notice was issued by Royal Borough of Kensington and Chelsea building control,” it adds.
The London fire is the most recent and deadliest in a series, from China to the Middle East, all linked to ACM.
In Dubai, for example, the 302-m-tall Address Downtown erupted into flames early last year, with more than 40 floors burning simultaneously.
The rapid external spread of flames was linked to aluminium cladding that contained combustible cores. Around 60,000 sq m of aluminium composite panels were used at The Address, according to locally based maker ALUMCO LLC.
It was Dubai’s third major tall-building conflagration in four years, prompting improvements in building codes, according to Probyn-Miers, a London-based architect specializing in dispute resolution.
A fire in Melbourne, Australia, revealed how the fragmented approach to cladding design, production and erection led to numerous buildings with noncompliant cladding. An audit by the Victorian Building Authority of Melbourne found that 51% of 170 high-rise residential and public buildings reviewed had noncompliant cladding. The audit followed a fire in late 2014 at the 21-floor Lacrosse Building, which was found to contain noncompliant Chinese-made composite cladding.
The revelation “clearly shows that there has been no incentive for building practitioners to comply with the rules and no enforcement to ensure they do so,” commented Scott Williams, CEO of the Fire Protection Association of Australia.
In the U.K., too, this kind of cladding “is a minefield of regulation,” notes an official at Bailey Total Building Envelope Ltd., Horsham. “Each project needs to be reviewed in its own right, and expert advice should be sought.”
The NFPA is developing a risk-assessment tool for high-rise buildings with combustible facades. The Grenfell Tower fire prompted the association to reach out to stakeholders in insurance firms and global engineering teams to identify key variables, such as wall materials and building fire-protection systems; characterize them in terms of risk or mitigation potential; and formulate an engineering-based risk model.
NFPA is fast-tracking the project, hoping to have the tool available by year-end.
