Manitoba Hydro Place
Cold Comfort: One of North America’s most complex energy-efficient buildings is also sited in one of its most challenging climates.
With the southern winds gusting across the prairie at speeds of up to 20 miles per hour, and the temperature well below zero Fahrenheit on a recent January afternoon, it challenged the imagination to accept that all of the toasty warmth of Manitoba Hydro Place was being generated by renewable sources—the sun and geothermal wells, supplemented by hydroelectric power. The building’s 18 floors of beautifully daylit offices were being continuously supplied with fresh air that was circulated through the workspaces only once. All of this was being accomplished where extremes in temperature and humidity are among the most challenging for any large city in the world, and yet the building’s energy consumption is predicted to be 66 percent lower than similar buildings here. Since September, the fully-metered building has been within 10 percent of that figure.
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To be sure, the building has been equipped with a wish list of systems: radiant ceilings, double-walled facades with operable windows, and geothermal wells to name a few. Not many projects of this type are completed without having their ambitions scaled back somewhere along the way, usually due to cost, technical complexity, or a failure of wills. Bruce Kuwabara, principal of Kuwabara Payne McKenna Blumberg Architects, recalls: “When I think back, there are so many ways this building could have been compromised. It is a miracle that we got almost everything we wanted.” He attributes much of the buy-in to the year-long integrated design process used, which included representatives of the owner and builders. Manitoba Hydro is a government-owned electric and natural gas utility, the fourth largest in Canada. Its recently retired manager for corporate services, Tom Gouldsborough, says, “You have to remember, it’s not signature architecture at any cost, or energy efficiency and sustainability at the expense of the functioning of the building or the staff. All these things have to work together.” Kuwabara remarks that while the building showcases the company’s commitment to sustainability, “they also did this for their staff, who are one of its biggest costs and the future of a company that wants to stay on the leading edge of its business.” He modestly adds that while interviewing for the project against several starchitects, “I thought we were never going to get the job, so I told them sustainability was important, but without signature architecture and ‘city-building,’ it’s not worth doing.”
After extensive programming and site analysis, the team evaluated dozens of massing schemes for the building, examining how each would be viewed from different parts of Winnipeg, as well as the impacts of bringing about 1,800 people downtown. Meanwhile, the project’s energy consultant, Thomas Auer of Transsolar Klima-Engineering, noticed something unusual about the climate here. “It was a shock,” he said, to find “that Winnipeg is basically sunny whenever it is cold. We couldn’t find a single cold city in the world with so many sun-hours, so there is no better location than this for a passive solar design.” As massing studies progressed, Transsolar modeled the way the proposed volumes might shade adjacent buildings and sites such as Air Canada Plaza, a large public space to the north, as well as the effects of wind and solar loads. Eventually the team chose a scheme with an 18-story office tower that rises over a three-story podium. Of all the schemes, it had the largest floorplate, but no office is more than 30 feet from a window.
The office tower’s plan is like a sharply pointed triangle. A pair of long, north-south oriented, column-free office blocks are set at angles to each other, separated by the service core. These office blocks face west and east-northeast. At the pointed north end, a solar chimney runs continuously from the ground level to several stories beyond the roof. Three south-facing, stacked six-story winter gardens form the short side of the triangle.
This orientation allows Winnipeg’s prevailing southern winds to naturally ventilate the structure. In winter, fresh air enters each winter garden through louvers in its south-facing, double-walled facade. Here the air is heated by the sun and humidified by the water features: 280 tensioned mylar ribbons that carry water from the ceiling to the floor. If necessary, air picks up additional heat from fan-coil units, then feeds the underfloor displacement-ventilation systems. It is also tempered by radiant ceilings heated by alcohol-based fluid. This heat is supplied in turn by chillers, whose source is a bank of 280, 400-foot deep geothermal wells drilled beneath the building. Air moves horizontally through the offices, finally reaching the solar chimney at the north end of the building through any one of nine two-story atria. In winter the air is is drawn downward through the solar chimney into heat-recovery units, then warms the parking garage beneath the building. The building’s double-walled facades consist of two low-iron glass curtainwalls, separated by a three-foot-wide air buffer. It holds in heat by preventing thermal bridging from the interior to the exterior.
In the summer much of the process is reversed. Water running down the mylar ribbons is now chilled to the point that it can dehumidify fresh air entering the winter garden. If necessary, additional cooling may be added before the air enters the underfloor displacement-ventilation system. Heat is also absorbed by the radiant ceilings, extracted by the chiller, then sent into the geothermal wells, warming the soil around them until heat is needed in the winter. As in winter, air flows from south to north, although now the stack-effect draws it upward and out the top of the solar chimney. To ensure that cool night air does not interrupt the stack effect, the sun’s heat is stored in 632 pipes filled with 17 tons of sand installed behind glass at the top of the chimney.
Whenever heat in the space between the double-walled facade rises to a certain threshold, the building management system opens operable windows in the exterior wall to vent it. Automated shades inside the curtainwall block out direct solar gain and glare, and the T5 fluorescent uplights dim when daylight exceeds certain levels; occupancy sensors turn them off when not needed. During shoulder seasons workers may manually open windows on the inside of the curtainwalls to introduce fresh air.
Because Manitoba Hydro’s technology is so fascinating, it is easy to forget that part of the story is the revitalization of the downtown, what Kuwabara calls “city building.” Bringing 1,800 workers here is an economic boon: in the course of a year they spend hundreds of thousands of dollars on shopping, eating, and entertainment. Tom Akerstream, the company’s manager of office facilities, notes that almost every employee used to drive, solo, to its suburban offices. “Now 68 percent take public transportation. And the three-story gallery, with its stunning architecture, water features, and barrier free access, is the most sought-after venue for downtown events. This great new public space has quickly become a focal point for Winnipeg life.”