Calgary, Alberta, Canada, is the self-proclaimed “Cowtown.” The former hub of the country’s cattle trade, it has a population that barely grazes the 1 million mark. Relief from its harsh winters comes only in the form of the mild but erratic chinook winds, which are also, unfortunately, notorious for triggering migraines among residents.
In this intersection of the Canadian Rockies and the Canadian Prairies, a skyscraper has been steadily rising in the downtown area for the past five years. Named after the river that curls through the Alberta province and the city center, the Bow, when completed this year, will be among the 75 or so tallest structures in the Western Hemisphere, and Canada’s largest skyscraper outside of Toronto. But the 236-meter- (775-foot-) high office building is more than just a sleek showpiece for the city. Rather, London-based architect Foster + Partners (F+P) and its collaborators designed the Bow to become a dynamic, sun-filled village within the often-snowbound city—an exemplar of a new class of skyscrapers that maximizes the well-being of occupants and of the world at large.
It’s no coincidence that the Bow is in Calgary. The first city in Canada to adopt a policy mandating that all public developments qualify for LEED certification, Calgary boasts a wind-powered public-transit system and a comprehensive, 100-year sustainability plan. ImagineCalgary, launched in 2005, combines energy-efficiency goals with proposed improvements to the city’s human-services infrastructure such as reducing energy consumption by 30 percent, eliminating indoor-air contaminants, and providing an environmentally friendly city for all Calgarians by 2036.
The plan’s emphasis on the connection between sustainable issues and the health and happiness of the citizenry is timely given the recent questions that have been raised about green building and its effect on occupants. As the pace of eco-building has picked up, its design standards continue to be challenged and redefined. Architects and engineers have been racing to grasp not only the latest building technologies—green roofs, passive ventilation, and rainwater harvesting—but also the technologies’ roles in a holistic system that connects the occupants physically and psychologically with the environment in which they live and work.
The U.S. Green Building Council (USGBC) has begun to research the relationship of LEED certification with the effects on human health for assessing a building’s environmental bona fides. The current LEED rating systems underscore this prospective link; a 2010 report by the USGBC Research Program estimates that up to half of the available LEED credits are related to the experience of building occupants.
Greener workplaces that produce a healthier workforce certainly seem possible. An additional up-front construction expenditure of 2 percent on sustainable features can lead to 20 percent in savings over time, part of which comes from increased employee productivity, according to a 2003 report from California’s Sustainable Buildings Task Force. Several studies have also linked daylighting to increased worker productivity and enhanced circadian rhythms.
The Bow is at the forefront of this push for eco- and health-conscious buildings. Rising from the center of Calgary, the curved structure is a soaring sculpture of glass and steel. Comprising 58 stories, including three floors for indoor gardens and two for retail, the 188,000-square-meter (2-million-square-foot) building occupies an entire city block.
The firm behind the Bow is known for designing environmentally sensitive buildings that also feel more sensitive for the people within. “We’ve learned a lot from … [London’s] Swiss Re and from Commerzbank … [in Frankfurt],” says Jim Barnes, F+P’s project architect, who worked with senior partner Nigel Dancey on the Bow. Building residents value the importance of interior greenery, views outdoors, and informal social spaces, all of which are included in the project.
The Bow is the first curved skyscraper in North America to use a triangular diagonal grid structure. The diagrid structural system, similar to the systems used in F+P’s Swiss Re building and the Hearst Building in New York, has become another characteristic of F+P’s high-rise projects, and with good reason. The technique improves the efficiency of the building’s support system, thereby reducing material resources and costs. The minimalist exoskeleton also allows for expansive windows, which translate to more natural light inside and views outside.
Expectations for the Bow were high from the start. The project had to fit in the urban context of Calgary, routinely ranked among The Economist’s top-five most-livable cities. Developed by H&R REIT, based in Downsville, Ontario, Canada, for tenants EnCana Corp., one of the largest natural-gas companies in North America, and spin-off company Cenovus, the Bow also needed to become an environment that occupants would perceive as comfortable and inviting.
F+P gathered a team of specialists to help them design a livable and dynamic office environment. The collaboration includes local design firm Zeidler Partnership as architect of record, Gensler’s Dallas office for the interior fit-out (with the exception of public spaces, which F+P designed), and New York–based M/E/P engineer Cosentini Associates, a Tetra Tech Co.
The designers’ sensitivity to the creation of an environment that fostered human wellness began with the building’s signature crescent shape. Beyond the skyrise status, Barnes says, “the overall massing was, frankly, solely designed around the end user.” The tower, an arch in plan that opens out to the south-southwest, pitches northward, pointing it “in the direction of the prevailing winds so it becomes more aerodynamic” and further reduces the material needed for structural bracing. More importantly, Barnes adds, “the aerodynamic shape also produces less downdraft, producing less turbulent winds at the base of the tower.” Building tenants hurrying across the southern entrance plaza to work won’t be buffeted by wintry gusts due to the protection offered by the tower, heavy landscaping, and entrance canopies.
The architects were also keen to capitalize on Mother Nature. Despite its northern setting, Calgary has the distinction of being Canada’s brightest major city—receiving 2,405 hours of sunshine per year. As a result, the Bow’s form provides many benefits to workers inside, says Paul Manno, AIA, Gensler’s design director. “You look at the shape of the building and it doesn’t seem obvious,” he notes, “but we maximized [the number of] perimeter offices. That inherently lets in more daylight due to the configuration.”
The structure’s parabolic envelope increases its surface area over that of a rectangular building with a comparably-sized footprint. As a result, more than 70 percent of employees in the Bow will have a window view. “The interior partitions of the office also have glass in them,” says Zeidler principal Katherine Robinson, “so light penetrates the center of the office floor plates,” which are 32,000 square feet in area.
Natural light is only one of many advantages to the building’s extensive glazing and orientation. Workers will also be able to take in views of the breathtaking landscape even at some distance from the windows, notes Steve Carruthers, Zeidler’s project architect. “When we say in Calgary ‘facing south,’ that means facing towards the mountains,” he says.
Whereas “in England,” Barnes notes, “a south-facing building would be a greenhouse.” Due to Calgary’s higher latitude, F+P—with guidance from its partners—was able to use the sun’s energy to integrate another system that is expected to reduce the Bow’s energy consumption by 23 percent from that of a baseline building: passive ventilation.
