Manitoba Hydro administrative tower in Winnipeg, Manitoba, Canada
Posted
10/6/2011
With temperature swings from -22 F to 86 F,
designers and engineers of the recently built Manitoba
Hydro administrative tower in Winnipeg, Manitoba, Canada,
set out to build an energy-efficient building that uses passive,
solar energy to power this groundbreaking, 700,000-square-foot
high-rise. The use of a double façade building envelope to trap the
sun's heat, along with radiant heating and cooling, displacement
ventilation and a high-efficiency central heating and cooling
system allow for optimal energy efficiency. Leaving no stone
unturned, large diameter, low speed Element fans from Lexington,
Ky.-based Big Ass Fans were installed to destratify the excessive
heat trapped at the upper levels of the atria, helping Manitoba
Hydro take full advantage of the building design.
The 3-foot-wide double façade wall system maximizes the southern
exposure and minimizes the effects of the chilly northern winds
that adversely affect the solar gains. According to Mark Pauls,
hydro energy engineer with Manitoba Hydro, there was much
trepidation in keeping a building made of a glass façade warm
without using too much energy. They had a very high standard for
insulating the building, using R-24 and R-30 on the walls because
of the extreme cold. Through the use of modeling software as a
design tool, they reversed the common mode for double paned windows
by installing the single pane on the inside and the double pane on
the outside. "The modeling gave us a lot of confidence into proving
these relatively new ideas for a cold climate," Pauls says. The
windowed façade has manually operated interior windows, automated
exterior windows and automated shades to provide ventilation. The
building's three southfacing, six-story atria operate as "lungs,"
providing 100 percent fresh air through a displacement ventilation
system.
Instead of recycling air, Manitoba Hydro introduces 100 percent
fresh air year round, regardless of outside temperatures. During
the colder months, the outside air is heated by a geothermal pump
system in the floors, and as a result, the hot air rises to the
ceilings in the three atria. At times, floor temperatures remained
50 F, while the ceiling temperatures settled at an uncomfortable 85
F. The operable windows at the top of the atria could have been
opened to allow some of the warm air to escape, but architects
wanted to find a way to use that excess heat more efficiently. To
eliminate this stratification, the large diameter, low speed
Element fans were installed in the 75-foot atria. Due to the large
volume of the space, the fans must run at a higher speed to move
the heated air to the floor, without a draft. With the fans running
close to full speed, the temperature discrepancy is now
5 degrees less.
"The Element fans mix the air, allowing us to minimize the
heating and cooling demand in the space," Pauls says. The tower
consumes 88 kWh/m²/a, compared to 400 kWh/m²/a for a typical large
scale North American office tower located in a more temperate
climate. Even though energy conservation was a focal point of the
overall design, employee comfort and satisfaction was the primary
concern. Considering cost associated with a workforce, Pauls notes
that all employee costs were considered in the development of the
tower. "Because our employee costs are roughly 100 times our
utility bill," he explains, "if we improve productivity and
decrease absenteeism by 1 percent each that dwarves any energy
savings we would ever see.".
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