INNOVATION January-February 2018

“My first reaction when I heard about it was concern about how something like that could happen,” says senior building science specialist, Mark Lawton, P.Eng., of Morrison Hershfield, “Aluminum composite panels are very common. So, when you hear the press reports of a major fire and saying aluminum composite panel, that raised alarm bells.” A cascade of events contributed to the severity of the Grenfell Tower fire, including a decision not to install automatic fire sprinklers in the building. Fire safety expert, Paul Atkins, told BBC London, “If they’d had a sprinkler system the fire would have been deluged before it got to the cladding.” Once the fire escaped the flat and set the cladding alight, the entire building was put at risk quickly. It appears the cladding type and the way it was installed had a major impact on the severity of the fire. THE WRONG COMBUSTIBLE CLADDING Stand on any street corner in downtown Vancouver and most of the high- rise towers you see have aluminum composite panels covering the exterior, explains Lawton, who sits on Engineers and Geoscientists BC’s Building Codes Committee and has over 20 years’ experience as a building envelope specialist. These composite metal panels, also known as ‘sandwich’ panels, have a plastic core with a thin, normally aluminum, metal ‘skin’ on the inside and outside. They are lightweight, easy to bend and shape with heat, quick to install, and can be custom-fabricated to a range of sizes and colours. These aluminum composite panels normally have a plastic core which classifies them as ‘combustible.’ The rules governing the use of combustible and non-combustible materials in construction are comprehensively laid out in the National Building Code of

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Many high-rise towers in BC have aluminum composite panels covering the exterior. High-rise towers built with metal or concrete frames may use combustible exterior cladding, so long as the cladding meets requirements specified by Canadian construction standards.

in Canada and around the world where it was evident the cladding had contributed to the spread of fire.” In an S134 test, the cladding to be tested is installed on a representative three-storey exterior wall with an opening to represent a window near its base. A flame is vented through the opening for a set amount of time and then extinguished. The cladding ignites and continues to burn after the flame is extinguished and the progression of the fire up the exterior wall is monitored and measured. The NBC sets limits on the height and intensity of the flame above the opening that the cladding must not exceed to be permitted for use in non-combustible construction. “It [the cladding on the Grenfell Tower] obviously didn’t perform,” concludes Steer, “If the combustible cladding used in the UK was required to meet similar performance criteria as in Canada, it suggests that the installation was inadequate.” Lawton agrees, “The foamed plastic insulation used in Grenfell would not be allowed under metal panel cladding under Canadian codes.”

Canada (NBC), the BC Building Code (BCBC) and the Vancouver Building By- law (VBBL). Combustible cladding, such as vinyl or wood siding, is permitted on wood-frame buildings, such as single- family dwellings, duplexes, townhouses, and four-storey apartment buildings, if they are sufficiently separated from adjacent buildings or property lines. Six- storey wood frame residential buildings are permitted and becoming more common; however the cladding on these buildings needs to adhere to the non- combustible requirements. High-rise towers built with metal or concrete frames, however, may use combustible exterior cladding, so long as the cladding passes a standardized test: CAN/ULC S134 Standard Method of Fire Test of Exterior Wall Assemblies . “The S134 test is based on a testing program developed by Natural Resources Canada in the 1980s,” says building fire specialist, David Steer, P.Eng., Principal at LMDG Building Code Consultants Ltd., “It was first published in 1992 and developed in response to a number of exterior fires that occurred

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