AECOM Canada/Crosier Kilgour & Partners Manitoba Hydro Downtown Office

At 64,000 square metres, Manitoba Hydro Place is the largest office building in Winnipeg. The 22-storey “cold climate sustainable” headquarters is home to 1,800 employees of Manitoba Hydro. The building integrates time-tested environmental concepts with advanced technologies to achieve a “living building” that responds to the local climate.

Even in Winnipeg’s extreme climate (-35C to +34C), the building maximizes the use of “passive” energy technologies and minimizes the use of “active” mechanical energy systems. Passive systems -such as south-facing winter gardens and a solar chimney -take advantage of natural processes to reduce the building’s use of energy.

Since opening in February 2009, The building has performed 64% more efficiently than a building designed to Canada’s Model National Energy Code for Buildings.

Manitoba Hydro required that the building should be designed using an integrated design process, whereby architects, engineers and others are all involved from the early stages.

Radiant Heat, Solar Chimney

The triangular shape of the building maximizes its exposure to the south and minimizes its exposure to the cold north, while narrow floor plates and tall floor-to-ceiling glazing allow sunlight to penetrate into the core.

A double facade curtain-wall system forms a 1-metre-wide buffer zone that insulates the building against the heat and cold outside. The buffer has manually operated windows in the inside wall, and vents in the exterior facade which automatically open when the building mechanical ventilation systems are shut down. Automated shades control glare and heat gain through the curtain wall.

The building’s thermal comfort relies on radiant surfaces in the building rather than traditional air heating and air conditioning. The exposed concrete ceilings have embedded plastic tubes that circulate heated or cooled water. The radiant heating provides superior comfort for the occupants, and it is more energy efficient than a traditional air system.

A 115-metre tall solar chimney on the north side marks the building entrance on Portage Avenue and is a key element in the passive ventilation system. It relies on the natural stack effect to draw used air out of the building during summer months. A solar absorber (thermal mass) assists the operation after sunset. In winter, exhaust air is drawn down to the bottom of the chimney by fans, and heat recovered from this exhaust air is used to warm the parkade and to preheat incoming cold air from the south atria.

100% Fresh Air, Geothermal System

In contrast to conventional North American buildings, Manitoba Hydro Place is ventilated with 100% fresh air whenever it is occupied. Within the splay of the two towers, a series of three six-storey south atria, or winter gardens, form the “lungs” of the building. They draw in outside air and pre-condition it to a minimum of +10C. The air is distributed at each floor level via an underfloor raised flooring system and rises through the space using displacement ventilation until it is exhausted by the solar chimney. Depending on the season, a 24-metre tall waterfall in each atria humidifies or dehumidifies the incoming air.

The building also has the largest closed-loop geothermal system in Manitoba. The exchanger is located completely below the structure and consists of 280 boreholes which penetrate 125 metres underground. Water from this system’s heat exchanger is circulated through the pipes in the concrete structure, providing radiant heating or cooling.

Structural System

The structural system was selected to provide the thermal mass for energy savings, and to provide large column-free floor plates that are flexible spaces for the occupants. The concrete structural frame consists of shallow and wide slab bands that span 11 metres. The combination provides a clean ceiling surface for better light reflectance and made it easier to install the radiant tubing.

Innovative ideas that came during the integrated design process sessions included adding a raised edge to the floor plate to allow for more daylight inside.

The building envelope was a critical feature. The double wall on the east and west elevations is a unitized system for ease and speed of erection. The north and south elevations have a similar system, but the glazing is a triple pane, low-iron glass for occupant comfort.

Revitalizing a City

With this building Manitoba Hydro has created a supportive workplace and revitalized Winnipeg’s downtown. The building reduces greenhouse gas emissions through its reduced energy consumption, and the utility will benefit from avoiding energy costs over the building’s anticipated 60-year life cycle. It uses 100 kwWh per square metre per year, whereas a typical Canadian building uses over 400 kWh per square metre.

Project name: Manitoba Hydro Downtown Office, Winnipeg

Award-winning firms: (mechanical & electrical engineers) AECOM Canada, Edmonton, Calgary & Winnipeg (John Munroe, P. Eng., Michael Shewchuk, P. Eng., Alan Aftanas, P. Eng.); (structural engineers) Crosier Kilgour & Partners, Winnipeg (Tom Malkiewicz)

Owner: Manitoba Hydro

Architects: KPMB, Smith Carter

Climate/energy engineer: Trans Solar Energietechnik

Other key players: PCL (construction), Hanscomb (costing), Prairie Architects (advocate architect), Halcrow Yolles (joint venture structural engineer), Natural Resources Canada (C-2000 advisor)