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On The Panel Thermal performance and architectural demands drive curtain wall and window wall innovations by Godfrey Budd A sleeker vision, involving more glass and an enhanced "wide-open" look, has been rippling through the curtain wall sector of late. In the view of David Borys, VP sales at Border Glass & Aluminum, manufacturers and architects these days are paying a lot of attention to esthetics. "Architects seem to want more glass and less aluminum, so cur- tain wall units are getting bigger," he says. Just over 20 years ago, four-by-five feet was the norm for modules or panels. Today, they measure up to seven-by-10 feet, he says. This makes for heavier units for installing. Most have double glazing, but some have triple glazing. The greater size imposes demands for more structural strength, so that thicker, stronger glass is needed. "At one time, the glass was five- or six- millimetres thick. Now, we're looking eight to 10 mil- limetres, with a laminate on at least one layer, maybe both," Borys says. Add to this the likelihood that with less aluminum, what there is may indeed need to be strengthened with steel. The result is that today's panels of 50 to 70 square feet can weigh orders of magnitude more than its predecessors of a decade or two ago. Inevitably, another result is that the cost for the glass component of a curtain wall increases. But the incremental dollars for glass in construction could mean future energy cost savings on the operational side. "As you decrease mullions and increase glass in a curtain wall system, you see overall thermal perfor- mance increase," Borys says. The esthetics of big glass are not confined to curtain walled office towers, however. They have also been spreading to the upper reaches of the residential sec- tor. "We're seeing people in big houses who want larger modules that residential window suppliers cannot do," Borys says. The office building curtain wall market remains Border Glass's primary focus, however, Borys notes that another result of the trend to bigger modules is that vertical structural mullions are getting bigger and deeper. On the thermal performance front, more com- posite materials are being used because of the thermal break properties. Fibreglass composite technology is central to EFCO's 8750XD unitized curtain wall, the latest addi- tion to the company's XTherm family of products, says Vince Harkins, a Canadian-based representative with EEBCon, which represents EFCO. The 8750XD system was introduced about a year ago and is designed as a high thermal performance curtain wall. "It uses fibreglass composite technology that provides structural heft and support and a ther- mal break," Harkins says. The fibre, which is called Duracast, is made in-house to better control costs, quality and supply. "By inte- grating fibreglass into the system, we're able to offer industry a leading U-value in thermal performance. The system allows for double- or triple-glazed insu- lated glass," Harkins says. He suggests, though, that the 8750 XD's thermal performance could obviate any need for triple glaz- ing. The frame or mullions have a 0.30 U-value and the centre of the glass (COG) a 0.24 U-value. "With this system, you get with double glazed what you get with triple glazed in some other systems. It's better for both office and condo applications. You gain value from the thermal performance. EEBCon wanted to add to the offer of options for improving thermal performance," Harkins says. EEBCon also has a "computer-based tool to assess precisely the potential thermal performance of this product within a specific design." From a standards and regulatory standpoint, the issue of envelope thermal performance varies in inten- sity across Canada. But, in Vancouver, thermal require- ments are tighter than anywhere else in the country, says Warren Elmer, director of operations at Glastech Glazing Contractors Ltd. This might seem strange to those unfamiliar with the intricacies of energy-related policy making, partic- ularly in regions like the Prairies where envelope ther- mal performance can have a greater impact because of the harsher climate. But, Elmer says, builders and developers on the Prairies have taken notice of Van- couver's push for energy efficiency and are putting more emphasis on thermally robust curtain wall. One such option is the Kawneer 7500 series cur- tain wall. The system is made in North America and is known as a high-calibre product that is good at han- dling extreme temperature swings. "A quality prod- uct like the 7500 was hardly ever used until about five years ago," says Elmer. The 7500 can accommodate a range of window options, among them Kawneer's A A 900 ISOWEB Window. The AA 900 window includes a polyamide thermal break and is mostly used for curtain wall and ribbon window systems, says Chris Lambert, an archi- tectural representative for Kawneer Company Canada Ltd. based in B.C. "One of the features of the AA 900 is its operable ventilation," he says. Kawneer's 1600 UT (ultra thermal) platform is another, more recent, curtain wall system that is also focused on thermal performance, as its name indicates. It is also less costly than the 7500 series, Lambert notes. Both product lines are made in North America. LEED continues to dictate the trend and Starline Architectural Windows remains a leader in energy efficient design-built window wall systems, with its primary markets being Western Canada and the Western U.S. "Our most popular system continues to be our 9000 Series Window Wall due to its proven performance with excellent value for the price and is now available with an SSG [Structural Silicone Glazing] option," says Mike Harrison, architectural representa- tive at Starline. "The 9000's energy efficiency is greatly enhanced in the 9003 Series, using triple glass and a much larger polyamide thermal break." Clients also have the option of the 9100 Series Flush Glazed Window Wall and the proprietary unitized cur- tain wall, that are all compatible with Starline's swing Above: The new residential wing at the Residences at The Ritz-Carlton, Montreal, is wrapped in an elegantly composed glass-and-steel envelope. Provencher Roy Architectes. Photo: Stéphane Groleau. Below: Before the renovation and expansion. Photo: Provencher Roy. Curtain Wall & Window Wall

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