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AUGUST 2018 | 13 Building Envelope PHOTOGRAPHY BY ERIC GERVAIS/COURTESY ENGINEERED ASSEMBLIES Building envelope systems improve comfort and provide energy savings by ROBIN BRUNET I t's no secret that two factors are chang- ing the way building envelopes are created. First is a change in tradition: historically, the building envelope accounted for a substan- tial portion of the total construction budget and was often assembled over a long duration involv- ing numerous trades. But the increasing drive to fast-forward construction schedules and save money has compelled envelope specialists to find quicker and more efficient ways to get the job done. The second factor is arguably more impactful: whether man-made or natural, Canada is experienc- ing more extreme shifts in weather than ever, which is placing a huge burden on building tolerances – and this in turn is causing engineers to rethink how building envelopes can be designed and constructed. Duncan Rowe, associate (Toronto) Building Science and Restoration for RJC Engineers, points out that conversations are taking place in which ideas that would not too long ago be rejected out of hand are now being seriously considered. He cites as an example a curtain wall rehabilita- tion of a 20-storey building in Toronto that his firm is currently presiding over. "We're using aluminum pressure plates as a curtain wall material, but at one point everyone was seriously considering the use of a polyamide pressure plate system for the curtain wall," he says. "Polyamide is usually used in ther- mal breaks within the curtain wall, but we wanted to expand its usage because of its terrific thermal per- formance and light weight." Unfortunately, the substance is also brittle, and while the engineers determined that given enough testing the material could be manipulated to accom- modate the curve of the curtain wall, the relatively short construction schedule negated its use. "But the point is, polyamide was considered by the developers to the extent the material was priced out," says Rowe. Jeff Ker, senior technical advisor for Engineered Assemblies, says, "Of late we've been heavily involved in thinking about facades of the future, what they will look like and how they will perform, and there are many challenges involved in making a building sus- tainable, enabling it to move so as to accommodate thermal fluctuations, and making it resilient," he says. The use of lighter materials is one way to help achieve the desired flexibility, but this contributes to a lower overall mass that doesn't necessarily result in superior structural resiliency; nor does the use of lighter material necessarily facilitate thermal efficiency. Ker and Engineered Assemblies have held indus- try discussions about the challenges, which he points out from a business viewpoint alone must be over- come. Under the Justin Trudeau government, proposals for any Government of Canada construction project must contain well-thought-out ways of accommodating weather extremes as well as a reduced carbon footprint. Tighten The Seal Parklex Facade wood wall panels from Engineered Assemblies.

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