Award of Excellence: York University Computer Science

Category: Buildings

KEEN ENGINEERING

The new Computer Science Building at York University in Toronto is a 10,700-m2 (115,000 s.f.), four-level building made up of computer laboratories, classrooms, lecture theatres and offices. All these components are connected through large atria. Keen Engineering was the mechanical consultant.

The high-tech building uses low-tech solutions to exceed the ASHRAE 90.1 standard for energy efficiency by 40%. Its sustainable design program overall resulted in it being one of three Canadian projects exhibited at the international Green Building Challenge held in the Netherlands in 2000. Many design measures and coordination between the client and design team have achieved the high environmental performance.

The energy saving measures include a high thermal mass in the cast-in-place concrete structure, an efficient building envelope, operable windows, atrium spaces and thermal ventilation stacks. The building form and orientation have been planned to be thermally efficient. A saw-toothed pattern on the east and west sides reduces the building’s exposure to direct solar radiation by redirecting incident solar load to the southeast and northwest respectively. This strategy also allows sufficient daylight to penetrate the workspace, resulting in reduced lighting, reduced cooling and a lower energy consumption. Overhangs for the theatres and cafeteria on the south exposure reduce glare and also reduce the need for cooling.

The decreased demand for heating and cooling energy resulted in a 50% reduction in the size of the mechanical equipment compared to a conventional solution. Consequently, over the 75-year lifespan, the green building is estimated to produce 85,700 tonnes less greenhouse gas emissions than a standard building. The building is expected to consume 1,940 MJ/m2 per year for prime energy, producing 67 kilograms per square metre of carbon dioxide.

Perhaps the most interesting design feature is the fact that the building is naturally ventilated — a challenge in the Toronto climate. The mixed mode approach has distributed fan coils serving the peak summer and winter loads, while natural ventilation and/or mechanically assisted ventilation serves the space and provides fresh air during the milder shoulder seasons. In the spring and fall seasons, when temperatures permit, the building opens up, allowing air to flow through operable windows into the classrooms and offices. The air is then relieved into the adjacent corridors that are connected with the atria.

The air transferred to the atria is relieved to the outdoors through high level openings. Wind, two ventilation stacks, and a direction/velocity sensor, control these high level operable windows in order to eliminate downdrafts. Smoke exhaust fans can be run at low speed in order to assist in ventilating the space.

In the summer/winter mode, the space is essentially “buttoned up” and mechanical systems are used. One air-handler delivers fresh, tempered air to the atria space. A second air-handling unit serves the two basement lecture theatres and the large theatre via an underfloor supply system.

Modular fan coils are used for the perimeter and internal spaces. These fan coils receive the fresh air from the atria, condition it and deliver it to the spaces. The air is then partially relieved back into the atria, and mixed with the fresh air delivered by the air-handling unit and the return air from the classrooms, offices and theatres. The remainder of the air delivered by the fan coils is exhausted through the roof to allow replenishing of fresh air. The atria are therefore indirectly conditioned by transferred air from the occupied space.

Other low-tech solutions include passive heat reclamation from the auditoriums, and passive pre-conditioning of the supply air from the underground supply duct. Displacement ventilation and stratification are used in the lecture halls.

Wood millwork is not only used as a work surface, but also as a supply air plenum and electrical chase, replacing the metal ductwork typically used with a natural, renewable resource.

Another feature is the sod roof, which retains storm water. Excess runoff is collected in a tank located on the roof and used for irrigating the landscaping.

Buildings can be constructed to the highest standards of efficiency, yet will not function at their potential because of the way they are operated and maintained. To circumvent this potential problem, a series of education and commissioning sessions were arranged and a detailed graphical user guide was developed outlining the unique operating features of the building.

The occupants can help to reduce the energy consumed by using the operable windows, and by accepting a broader range of temperatures and humidity conditions than are normal. Public awareness of sustainable concepts through projects like this will benefit society and, particularly, the younger generation.

The cost for the mechanical systems was $2.2 million, compared to a budget of $2.0 million, the difference due to requests for additional equipment. The building’s total cost was $18.5 million, compared to a $17.5 million budget.

The building was completed on time and has been occupied since September 2001. After a winter of operation it was determined that the passive heat reclamation system through the lecture hall works well. Refinement of temperatures in the central atria is ongoing, but in general, the system performs as per the design intent.

Name of project: York University Computer Science Building

Photography: Steven Evans