Power for artificial lighting can represent 20 to 40% of a building’s total power use. Through careful building orientation and design, this demand can be substantially reduced, and at the same time dramatically increase the quality of the space.
Studies have shown that people are happier and more productive when they are exposed to natural sunlight during the course of their workday as opposed to artificial light. In 1999, the California Board of Energy Efficiency commissioned a study and found that increased productivity, increased wellness, and reduced energy costs resulted from companies using natural lighting instead of artificial light.
Manitoba Hydro features an unusual floor plate configuration, which ensures light reaches all the way to the core of the building. Shaped like a capital ‘A’, the building houses the bulk of the office space in column-free, outboard office loft spaces. Floor-plate depths are kept shallow, with terraces and atria cutting strategically into the building and ensuring that all occupants have access to natural light. The slightly higher than average floor to floor heights at Manitoba Hydro (4m), in combination with a shaped slab edge step at the East and West double skin facades ‘pry’ open the typical office loft to let light penetrate deeper into the space.
Full height glazing throughout the workspaces allows for unobstructed views, while a fully automated louvre shading system within the double-facade stops unwanted solar gain when appropriate. The angle of the 100mm deep louvre shades can be adjusted as required to suit sun location and angle. When light levels are low enough, the louver system can be fully retracted and stacked tight against the ceiling in the step of the slab. Computer models of the surrounding tall buildings, in combination with active real-time data from the building’s weather station optimize the blade angle and determine how each louver shade should be deployed. The top portion of the shade assembly is set at a different angle from the lower blades to act as a series of small light shelves, bouncing light onto the white ceiling, while the lower portion is closed. When fully deployed, the aluminum louver blades feature a finely perforated surface, stopping solar glare, but still allowing views to the outside. Areas of the building that receive higher amounts of sun (such as the south loft tips and the south atrium interior glazing) receive a permanent ceramic frit pattern to reduce solar glare and gain.
To accurately test the building’s daylight efficiency, the design team completed extensive modelling, both digital and physical, to more fully understand how the space would function on a day to day basis. Each potential scheme was tested using computer modeling to determine the “daylight autonomy” of each floor plate over an entire solar year. Daylight autonomy can be most simply understood as ‘the percentage of time, during a normal business day, that overhead lighting would be required, assuming a minimum light level of 300lux’. By altering factors such as building orientation, window placement and floor to ceiling heights, the team was able to quickly understand the efficacy of key design moves.
Once the form of the building had been established, a highly accurate 1:20 scale model of the typical office loft, was built and tested in a ‘heliodon’, (an accurate day-lighting simulator) at Concordia University in Montreal. Feedback from the heliodon testing allowed the team and the client to see exactly how a number of different factors, such as furniture configuration, partition height and location, different louver options, and even wall and carpet colour would impact the space.
Related Performance Goals:
Energy Performance-Sustainable Design
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