By Yves Levesque, Ing., S.M. GROUP INTERNATIONAL (SMi)
Sherbrooke University Longueuil CampusBuildings Building Mechanical & Electrical (HVAC) Systems Building Structure
With the completion of the Longueuil Campus of the Université de Sherbrooke, the new downtown core of the city of Longueuil in the Montreal South Shore region has entered an era of avant-garde design and sustainable development....
With the completion of the Longueuil Campus of the Université de Sherbrooke, the new downtown core of the city of Longueuil in the Montreal South Shore region has entered an era of avant-garde design and sustainable development. Officially opened in February 2010, the $125-million complex accommodates 3,000 students, with classrooms, laboratories and offices for several faculties, including law, medicine and engineering.
SMi were the structural engineers of the building. Marosi + Troy, Jodoin Lamarre Pratte, and Labbé were the architects.
The monumental above-ground complex covers the site’s entire surface area. It consists of a 16-storey tower; a four-storey unit designed for a future extension of four additional storeys; a two-storey zone with an exterior garden or “Oasis”; and an atrium with a glass canopy and an exposed steel structure. The atrium connects to the adjacent AMT bus station and Longueuil metro station.
A structural frame of 9 x 9 m was established for the complex. It incorporates two- way reinforced concrete slabs with drop panels for most floor levels. The 3½ floors of underground parking within the peripheral foundation walls constitute a single solid, rigid structural block ensuring the lateral stability of all the structural sub-units.
At the entrance to the main tower is a five-storey open space — the “vertical campus promenade” — which includes a long steel staircase and a high glazed wall overlooking the Oasis garden. The design of the five-storey space was a technical challenge. The provision of movable joints between the structural units required a curtain wall structure fixed to the upper floors of the tower and attached at the base to the adjacent structure also by movable joints in all horizontal directions.
The long staircase was the subject of a step-by-step dynamic analysis with simulations of “step impact” and rhythmic activity in order to ensure vibrations would not be a problem. A grid-type model was used to simulate the rigidity of all the components of these stairs.
With its exposed steel space-frame structure supporting a glass roof and the facades, the atrium is the jewel of the project. Its steel structure is supported on the ground floor on three sides, and is supported on the second floor of the building by the wide span reinforced concrete and 9 x 9 m structural frame of the Oasis garden.
The atrium’s special support structure constituted a significant technical design challenge. Load transfer in the roof diaphragm was facilitated by the installation of robust, rigid steel beams hidden in the water discharge drains on the roof.
The support structures of the front and rear glazed facades were designed as suspended elements with side and bottom supports that are mobile in the vertical plane of the facades. Different models with semi-detached and detached buildings were considered, and the worst conditions of each simulation were used in the design for lateral wind and earthquake loads.
Innovative Mechanical & Electrical Engineering
Built in Longueuil’s city centre, Sherbrooke University’s new campus building is one of the tallest structures on Montreal’s South Shore. The new building includes a 16-storey tower and other components with a total floor area of 61,000 square metres.
Determined to create an eco- friendly building, DESSAU took a unique approach in engineering the heating, ventilation and air-conditioning (HVAC) systems. The HVAC design reduced energy consumption by 45% (350,000 m3 of natural gas and 1.1 million kWh of electricity) compared to a standard similar building, consequently saving over $250,000 a year on energy bills. When including government subsidies, the return on investment for energy-saving equipment is less than two years.
The building’s heating system relies on geothermal energy. A total of 37 vertical geothermal wells were installed on site, each of which is 183 metres deep. Although conventional geothermal boreholes are approximately 150 metres deep, DESSAU opted for deeper boreholes so that the overall quantity could be reduced. This was important given that space was restricted due to the area’s density. The geothermal boreholes provide 24% of the building’s heat capacity using clean, renewable energy.
DESSAU pushed the concept one step further and through the use of innovative equipment and design strategies they massively reduced the amount of energy wasted. For example, rotary air-to-air heat exchangers (enthalpy wheels) transfer sensible and latent heat from the outgoing air to the fresh incoming air with an average efficiency of 79%. Run-around coils were installed in contaminated air exhaust ducts (from places such as the kitchen) to recover heat without degrading the incoming air quality.
Most typical buildings need cooling in their central areas year round — even in winter temperatures — because of heat gains from sources such as lights, appliances and occupants. It is very common to see mechanical systems heat and cool different areas of a building simultaneously. Typically, buildings reject their excess heat outside by means of air condensers or cooling towers. At the new Longueuil campus, however, the HVAC system incorporates heat recovery chillers linked to a low temperature heating loop. The system redirects excess heat from the centre of the building to other areas that need heat, acting much like a heat pump.
Residual heat is supplied by boilers. Four natural gas, high-efficiency condensing boilers recover heat from the exhaust gases, consequently increasing their efficiency up to 95%. Finally, an electrical boiler is used during off-peak hours.
Mechanical 3D Design
To avoid delays and additional costs resulting from on-site adjustments during construction, all plans for the main mechanical room on the building’s top floor were prepared using AutoCAD MEP with 3D models. This software helped to coordinate the various trades and engineering disciplines and prevented a large number of unexpected events happening on the work site.
The unique design was made possible through effective energy simulation software like DOE2.1e and TRNSYS. The simulation software allowed the designers to model and analyze the building’s hourly energy use. It simultaneously takes into account weather data, building envelope parameters and complex building HVAC system interactions that are almost impossible to estimate using traditional calculation methods.
In the end, the designers determined that integrating geothermal energy with heat recovery equipment was well worth the initial investment.
The significant energy savings contribute to reducing greenhouse gas emissions by 655 tons per year. However, the designers also wanted to lessen the building’s ecological footprint. Consequently, they decided to integrate vegetation into a part of the building’s roof. Green roofs have many environmental benefits, espe cially in urban areas where they help diminish heat islands, filter pollutants and carbon dioxide, and reduce storm water run-off.
Other green design features include reduced-flow toilets (4.8 litres/ flush) and the collection of rainwater for the green roof water basin. These initiatives reduce the building’s water consumption by 20%.
As a whole, the Longueuil campus building is a good example of sustainable development technologies that could easily be applied to future buildings.
Client: Sherbrooke University. Structural engineers: S.M. Group International (SMi) (Jacques Guertin, ing., Yves Levesque, ing., Steve Chamberland, ing.) Mechanical/electrical engineers: DESSAU (Hélène
Rheault, ing., René Dansereau, Michel Gendron, ing., Pier-Luc Vinet-Thibault, ing.) Architects: Marosi-Troy/Jodoin-Lamarre-Pratte/Labbé Project management: CIMA+