Metallic cladding scrutinized
Insulation on high-rises has fed other fires
For the last decade, engineers specializing in fire safety have worried about the hidden danger posed by the kind of insulated metallic skin that transported flames up a high-rise apartment building in London, killing dozens.
Panels of the armorlike “cladding” have become a popular facade on tall buildings worldwide, both for their sleek look and energy-saving virtues. They also have helped fuel spectacular infernos in the Middle East, Europe, Asia and the United States.
Some fire experts worry that, with energy efficiency a priority worldwide, the proliferation of “green” buildings has the unintended consequence of fanning fire danger. Though cladding can be flame-resistant, the result can be deadly when it is not.
“The good intent of sustainability translates into a potential fire safety problem,” said Brian Meacham, a fire protection engineering professor at Worcester Polytechnic Institute in Massachusetts.
At London’s Grenfell Tower, flames raced with alarming speed up 24 stories of cladding in which a plastic core was sandwiched between thin sheets of aluminum. That composite is one of several kinds of exterior paneling that help moderate inside temperatures, saving on energy needed for heating and cooling.
The tower’s aging concrete facade received the facelift last year as part of a $13 million publicly funded refurbishment effort aimed, in part, at making the building more energy efficient.
The tower burned Wednesday. At least 58 people were confirmed or presumed dead, a tally that could rise.
Authorities are still investigating the fire. Its behavior strongly implicated the cladding, several fire safety experts said in interviews. Anger has mounted in the community following reports that contractors had used cheaper panels in which the plastic insulation was not fire-resistant.
Cladding with pure plastic insulation costs less and insulates better than an alternative that incorporates fire-slowing minerals, experts said. On short buildings, it makes sense.
Not so for taller buildings. The International Building Code — a model adopted widely in the U.S., some areas of the Middle East and the Americas — calls for the use of fire-resistant cores in buildings over 40 feet tall. The code in England is less specific, giving architects latitude in how they make sure exterior insulation is safe as long as “the external walls of the building shall adequately resist the spread of fire.”