Greenstone Building, Yellowknife

Located in downtown Yellowknife, capital of the Northwest Territories, the Greenstone Building’s energy savings are expected to save Canadian taxpayers $70,000 per year. The reduction in greenhouse gas emissions is calculated to be 370 tonnes per year.

Opened in October 2005, the building accommodates 200 employees in 6,800 square metres. The four-storey cast-in-place concrete structure is formed as two wings around a central elevator core, with rounded stair towers at each end.

As a sustainable building it is designed to minimize the demand on the earth’s resources, so it is durable and expected to last 75 years. It is also designed to be flexible, so that any future changes in its use can be met without major construction.

“Green” features are integrated at every level of the design. For eample, it has a vegetative roof to retain stormwater run-off. This run-off together with water from an underground aquifer is collected in a 4,500-litre basement tank and used for the toilets. Potable water use in the building is 153 litres per square metre, 35% less than the LEED baseline.

On the south facade, photovoltaic panels are integrated into the curtain wall. The solar cells are laminated between two sheets of glass and placed on the exterior side of the units. This solar system is expected to generate 33 kilowatts to heat domestic water, reducing electrical demand by 5%.

Mechanical systems

Operable windows provide free ventilation, and the building has underfloor air distribution with a four pipe fan coil system. The fan coils are located in the 610-mm access floor plenum, and each is supplied with outside air through a pressure independent variable air volume box controller. There are independent zoning temperature controls.

Introducing air from below rather than from above increases the ventilation efficiency by using natural convection. The air quality also benefits, since supply air and pollutants are mixing above the “breathing zone.” Another energy saving is achieved because the air supply can be warmer: 16-18 C, compared to an overhead system, which would be set at 12.5-14.5 C. And the fan power required to force air through the system is less than in an overhead supply system.

High-efficiency condensing boilers are used for heating the building, and cooling is by a high efficiency air cooled condensing chiller system. The cooling load capacity is only 29 watts per square metre.

The building is reported to be operating well. It has a forecasted energy performance 56% better than Ashrae 90.1-1999. It was also designed to achieve LEED gold certification. The application is still pending.

Structural & mechanical: A.D. Williams Engineering, Edmonton (Edward Lazar, P.Eng., Brian George, P.Eng., Elaine Carr, P.Eng., Adrianna Landberg, P.Eng.)

Electrical: Keen Engineering

Architect: Manasc Isaac Architects

Energy consultant: G.F. Shymko & Associates

Photos courtesy Manasc Isaac Architects