Most innovative energy efficient glass project

The Bow, EnCana Corporate Headquarters, Zeidler Partnership Architects

At a height of 775 feet, The Bow, the newly constructed headquarters for EnCana Corp., is Calgary’s tallest building. The 58-story structure draws its name from both its crescent-shaped façade and its location along the city’s Bow River.

The distinctive curved shape of The Bow and its site orientation are designed to help the tower deal effectively with winter and summer wind patterns and to enhance its sustainability and energy performance. Energy savings are produced by a south-facing atrium that traverses the full height of the structure and functions as a tempered buffer zone, transmitting heat into the building and offsetting the need for more conventional mechanical heating and ventilation requirements. The exterior face of the south-facing atrium's curtain wall incorporates Viracon VE1-2M glass, also used in the Type 4 curtain wall at the north stair. 

EnCana officials expect the energy efficient design of The Bow to reduce energy use by about 30 percent, compared to a conventional office tower. The curved footprint of the building also is designed to maximize daylighting and views.

James Barnes, an associate with the design architect, Foster+Partners of London, said that “by using the triangular diagrid structure, we were able to create a near column-free space within the building that allowed for a very flexible floor plate.” Not only does the column-free design enable project teams to sit together, which was one of EnCana’s requested specifications, it also allows 85 percent to 90 percent of the offices to be located near the perimeter of the building, according to officials from executive project architect Zeidler Partnership Architects.

PPG Industries's Cradle-to-Cradle certified Solarban z50 glass was used in the curtain wall on the building's north façade, as well as in the ground-floor curtain wall along the north side. Solarban z50 glass was selected for the project because of its distinctive steel blue-gray appearance as well as its ability to fulfill The Bow’s need for daylighting, unobstructed views and energy performance, according to Zeidler officials. With visible light transmittance of 51 percent and a solar heat gain coefficient of 0.31, Solarban z50 glass offers a light-to-solar-gain ratio of 1.70 in a standard 1-inch insulating glass unit, the highest of any architectural glass in its category, according to Zeidler.

Sota Glazing designed and manufactured the curtain-wall system for the exterior and interior south atrium facades, pictured. Alberta Glass was the installer. 

In addition, Oldcastle BuildingEnvelope was responsible for the design, fabrication and glazing of the curtain-wall systems on The Bow’s North, East and West elevations—from ground floor to roof—including the two pedestrian bridges. Gensler provided interior design and programming.