Lassonde Pavilions

Bouthillette Parizeau, Pageau Morel, Pasquin St-Jean

In 2002, the Ecole Polytechnique de Montral, the largest engineering school in Quebec, and second largest in Canada, decided to expand its facilities with new buildings that would closely follow sustainable development concepts.

The expansion consists of the 32,700-sq.m Lassonde Pavilions, which are two pavilions separated by an atrium, and a 6,600-sq.m indoor parking lot. The total construction cost $75 million, and includes several auditoriums, classrooms, teaching and research laboratories, teachers’ offices and a large library.

While the consortium of Bouthillete Parizeau Associates (BPA) and Pageau Morel Associates (PMA) developed the engineering for the mechanical and electrical systems, Pasquin St-Jean & Associates was responsible for structural and civil engineering.

LEED Gold

The Lassonde building’s energy performance is 60% more efficient than the standards of the Model National Energy Code of Canada for Buildings. Its energy costs are at least 53% lower than the ASHRAE 90.1-1999 standard.

Also, with a LEED (Leadership in Energy and Environmental Design) score of 46 points — the highest Canadian score to date — the building received a Gold LEED rating by the U.S. Green Building Council, becoming a benchmark in sustainable construction.

LEED certification includes several aspects: the ecological site layout, efficient water management, energy and air conservation, re-use of material and resources, indoor environment quality and innovation.

With a LEED project designers must innovate on every level and work much harder than with traditional designs.

Energy and electro-mechanical

The electro-mechanical systems had to be flexible and adapt to a variety of occupancy rates and schedules. The city of Montreal required that no equipment be installed on the roof. Meanwhile, the organization of the conduit runs between the pavilions through the atrium added to the project complexity.

Taking up the energy challenge, the consulting engineers chose a system that recovers heat from the chimney stacks of the Polytechnique’s main building. This recovered heat supplies free energy to meet approximately two-thirds of the new building’s needs.

In summer, the energy saving strategy is designed so that the heat evacuated from the mechanical chillers is used to meet the minimum heating requirements for user comfort — in occupied spaces only. Excess heat is evacuated outdoors through cooling towers, one of which has a variable frequency drive to reduce the amount of power required.

Offices and classrooms that are not used on a continuous basis are equipped with occupancy sensors. These turn off the lights and reduce the ventilation air flow when no-one is present.

All the roof and drainage water is recovered in an underground cistern. This water is then filtered, chlorinated and directed to the lavatories. Domestic water for these is only used when the storage tank is empty, thus reducing sanitary water consumption by 92% compared to a conventional building.

Complex structure

Built not only on the side of a mountain but literally embedded into it, the Lassonde pavilions are a unique construction. While the north entrance is at ground level, the same floor becomes the sixth basement at the rear of the building.

With an excavation depth of 30 metres and pressure from the surrounding ground, the building required foundation walls up to one metre thick, coupled with rock anchorage. The lower floors of the building are extremely complex in structure, housing several large auditoriums with a clear span of nearly 14 metres without interior pillars. And a large number of structural systems were necessary to meet the architectural and mechanical requirements.

The pillars and floors of the seven upper levels are supported by beams that are 1,275 mm in height and have a span of 14 metres. Post-tensioned beams allow a maximum use of high strength concrete. Moreover, a progressive stressing sequence made it possible to remove supports quickly and proceed with the construction of the higher floors.

The execution of the project required over 20,000 sq.m of concrete with a strength of up to 55 MPa. For LEED certification, 27 different concrete mixtures were necessary to cover all the possible usage, resistance, positioning and temperature conditions, including three-component concrete and silica fume cement.

Name of project: Pavillons Lassonde, Ecole Polytechnique de Montral

Award-winning firms: Bouthillette Parizeau Assoc. (Pierre Roussel, ing.) and Pageau Morel Assoc. (Gilbert Lavoie, ing.) mechanical-electrical consultants; Pasquin St-Jean Assoc. (Normand Leboeuf, ing.) structural consultants

Owner: Ecole Polytechnique de Montral

Suppliers: Delta-Regulvar; ITT Industries