Lightweight Precast System Transforms High-Tech Student Residences in Montreal

Like a high-tech beehive, a new and modern dormitory at Montreal's famed engineering school uses a modular pattern of SlenderWall lightweight precast panels with integral interior wall framing and closed-cell foam insulation.

Located in downtown Montreal, the École de Technologie Supérieure (ETS) is a magnet for future engineers, graduating enough to be the fourth-ranked in all of Canada. The school has been growing, too, as part of the University of Quebec's big expansion plans.

For a new, nine-story residential complex, ETS officials turned to Régis Côté and Associates, Architects, one of Montreal's top firms and a frequent design signature on the campus. The firm, led by principal architect and design director Serge Jacques, conceived a new residential pavilion to connect to adjoining dormitories by means of elevated walkways and tunnels. Inspired by the lively, busy campus, Jacques envisaged a "high-tech beehive, that would have its own unique pattern of technology," he explains. "The colors and window shapes in the grid are varied to establish the pattern, which indicates the types of rooms and uses."

The lighter grey sections of the façade, for example, indicate the locations of one-bed studios; for all rooms or suites, horizontally oriented windows are located above desks or work surfaces, so that seated students can enjoy panoramic views as a break from studying.  The top floor panels are larger, reflecting the two-story penthouse suites they contain. Yet all the light grey, middle-weight grey and very dark grey surfaces – practically black, from a distance – are clearly of the same enclosure system: SlenderWall (an Easi-Set Worldwide licensed product), the thin-profile precast panels with factory-installed windows. The cladding system is backed by steel framing that doubles as perimeter stud walls, with a continuous 3-inch layer of factory-installed, closed-cell foam thermal insulation.

All the materials were selected to be consistent with the university's sustainability goals – and favorable in terms of cost-benefit ratio, according to ETS project planners. The panelized cladding is attached to concrete floor slabs and narrow columns.

"SlenderWall was a very good choice, in part because it was highly economical," says Jacques. "Also, the project had to be built over the course of the winter, and the wall system came finished with windows in place and pre-framed interior walls." Jacques notes that this is his first project using precast, and his first using SlenderWall. Yet, with his inventive, modular design, only a few panel styles had to be cast, making it even more cost-effective than expected: the repetitive panels are flipped or rotated as needed to achieve the varied yet rhythmic look envisaged by the Régis Côté design team.

Showcase technology for engineering school

Early in the project planning phases, the well-regarded precaster, Alma-based BPDL, had begun cultivating interest in the precast system among campus officials and the architects. "One of the main advantages for SlenderWall is that the project leaders were interested in a new technology that was not very widely used," says Guy Tremblay, technical director for BPDL, explaining that it would be educational for the students. "This is the kind of thing that ETS likes to promote in their new school projects."

Yet there were lots of other advantages. For example, the factory-installed windows reduced jobsite work and shortened the project schedule significantly. With the concrete structure, the precast cladding offered advantages for fire-rated separations as well as acoustical isolation. A special connection detail would both speed and enhance structural attachments, designed by the architects with the structural engineer, Pasquin St-Jean of Montreal. Last, the closed-cell spray foam would add significantly to the enclosure's thermal performance.

According to Tremblay, the SlenderWall precast system also helped address a scheduling challenge, when the Régis Côté design team and precaster were simultaneously designing and casting panels to comply with an aggressive timeframe. Installation averaged about 15 panels per day during the accelerated phase, according to the general contractor, Montreal's Decarel. In all, the team produced 479 precast panels with 753 pre-installed windows, with the average panel of about 170 square feet in size and weighing just more than 4,000 pounds – very lightweight as compared to conventional precast.

In terms of design appeal, Jacques adds, the architects worked to create a radical palette with the precast system. "The color is integral to the concrete, which is ideal for durability and life cycle," he explains. "The light color we chose is the lightest the grey cement can do, and the dark grey is the darkest they can do using grey cement. You can't achieve a pure white or pure black concrete mix, because with too much color the concrete will not harden properly."

On- and off-campus

The resulting building covers a high-profile block with the façade exposed to three streets. The building encloses a new courtyard, bringing in ample light and air – as well as an outdoor recreation and study zone – for the hard-working engineering students. The building connects by pedestrian bridge on one corner, where it sits adjacent and in decided contrast to typical red-brick Montreal rowhouses.

The application of SlenderWall for university buildings and dormitories is a growing niche, says Moffette Tharpe, Managing Director with Easi-Set Industries, which licenses SlenderWall to qualified producers. "We've seen BPDL grow to meet an increasing demand in Montreal for Slenderwall, including hotels like the city's Hilton Garden Inn, a mixed-use high rise with two-toned concrete, as well as new office and condominium buildings," he explains. "This hybrid system, with its pre-applied insulation and prefabricated wall framing, brings all the advantages of concrete along with light-gauge steel to residential and other occupancies."

For Tremblay, who frequently ships SlenderWall panels hundreds of miles away to Boston and New York City, the system remains competitive even for these long-distance projects. "Even though the architects often drive this product choice, there are so many advantages on the jobsite that it makes sense to transport them those long distances," he explains. "First, they are very efficient for amount of area you can enclose in a short time in winter conditions: just install the panels, seal the joints, and then you're ready for the next trades."

Other advantages listed by Tremblay include the light panel weight, which reduces the dimensions and costs for shear walls and structural joints. A typical 5-inch precast façade weighs about 65 pounds per square foot, while the SlenderWall is only 28 lbs. "This affects not just dead load but also the seismic load, and building codes in Quebec and on the East Coast call for seismic designs," says Tremblay.

For the ETS dormitory – the first project by BPDL to use factory-installed window units – there are new advantages for quality control and improved adhesion and integration of the window-wall interface. "Every single joint can be inspected to ensure the surfaces are clean and that we get the best possible bond between the window and the precast opening," says Tremblay. It's also easier to inspect for quality and code compliance, right in the comfort of the precast plant.

Work on the jobsite is eased significantly by the use of lightweight, integral SlenderWall panels, as the University of Quebec learned. Some 30 different types of windows were installed before the SlenderWall panels were even hoisted into place. The footprint of the building was constrained by the lot line and neighboring structures, and BPDL used only a small, 60-ton mobile crane rather than a larger tower crane or a 90- to 120-ton mobile lift. This helped speed the work with few moves, as the crane could carry the panels deep over the site footprint as far as 15 feet away.

While the ETS dormitory is a groundbreaking project in many ways, its combination of efficiency and repeatability with a memorable, contemporary aesthetic makes it a landmark effort for the prestigious École de technologie supérieure. With one enclosure system choice, the architect was able to achieve the look of the high-end, "high-tech beehive" with a sophisticated construction technology befitting a top engineering school.

Unknown to most students, however, is how the flexibility and sustainability of SlenderWall also serve the school's mission.

Project Facts: ETS Dormitory

Building:   174,000 square feet of dormitories

Project type:  Higher education residences (new construction)

Location:  Montreal

Design challenge:  Modular panels with pre-installed windows, architectural

finish and good thermal insulation; large site footprint.

Delivery type:  Bid

Total project cost: $26 million

Architects:  Régis Côté and Associates, Architects

General contractor: Reliance

Precaster:  BPDL, Montreal

Slenderwall® Architectural Precast Specs

Number of panels: 479 total precast panels averaging 4,000 pounds and 172.2

square feet per panel, totaling about 82,400 square feet with 753 pre-installed windows

Panel type:  Three-color panels in 32 different window configurations, with

factory-applied R-21 closed-cell foam and factory-installed windows

Panel finish:  Three colors: light, medium and dark grey; textural finish

Installation period: About 40 days

Installation date: 2010 - 2012

Manufacturer: BPDL (manufacturer/fabricator); EasiSet Worldwide


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