Rising 25-storeys over the tranquility of Nun’s Island, just off the southeastern tip of Montreal Island proper, are the twin towers of a Proment Corporation condominium development known as Le Vistal, each encompassing some 160 units. These buildings are special, because of their levels of luxury and workmanship, yes, but also because in Canada, as of the fall of 2008, just 61 high-rise buildings have registered to be LEED Certified. Of those 61, just three have received that certification. Le Vistal is about to breathe that rare air, becoming the first high-rise building in Quebec to do so.

As Proment President Samuel Gewurz said recently, although he is exceedingly proud of Le Vistal’s aesthetic qualities and wonderful location, it is what people don’t see that make Le Vistal’s buildings remarkable. For example, Le Vistal is the largest residential building in Quebec to employ geothermal heating and cooling. Above grade, the mostly glass exterior utilizes two kinds of double-glazed glass – insulating on the north, and reflective on the south. To further conserve energy, the exterior envelope of the building is sealed tight.

At a recent gathering to celebrate the opening of Tower One, according to a story filed by Henry Aubin in The Gazette, Proment Vice President of Development and Construction Louis-Joseph Papineau pointed out that since the project was launched in September 2006, he has noticed a dynamic evolution in the construction industry, noting that "more and more green materials are available to us especially for the finishing."

One such green material – a material particularly suited to the LEED aspirations of the project – is precast concrete. "We like precast," Papineau announced when contacted by Imagineering. "We’ve been developing on our little island here for the last 25 years," he says, "and most of our buildings are done with precast. One of the advantages for us is that we have two good precast fabricators here in Quebec – Beton Du Lac and Saramac – so we qualify for LEED credits for regional content as we go for LEED Gold status on this one. We’ve been dealing with these companies for a long time, and we like the advantages of precast for the skin. We like it for the speed of erection, the quality, durability and all of the other advantages, including the fact that with precast, you can dial in the quantity of recycled material."

Robert Bouchard, Vice President of precast fabricator Béton Préfabriqués du Lac Inc, says that crushed granite was used for the aggregate, adding that his company is very proud of its long-standing relationship with Proment, particularly because both companies make GREEN a priority. "One of the things we do here is that we don’t sandblast outside like most precasters do," he says. "Here, we sandblast inside in a chamber so that the dust is contained better, which is fairly unique to precasters, I think, because it’s something we (engineered). I also think it’s the future, because it’s important to produce a green product, but it’s also important to produce it in a green way." Papineau adds that Béton Préfabriqués du Lac Inc tried to optimize panel engineering in order to decrease waste in transport and in the erection and fabrication stages, to have maximum repetition so the molds could be used as many times as possible.

In taking this GREEN approach, Papineau emphasizes that it was important to the builder to source its materiel regionally. "Everything is regional," he says, "because the reduction of transport is a big factor. The fact that with precast there is a minimum of wastage as opposed to other cladding materials, and the durability, speed of erection, as well as the efficiency of the material are all factors that the use of precast, specifically, contributes to the green aspect of the building."

The green aspect of Le Vistal also figured into aesthetic decisions. Principle architect Jean Pierre Bart of Jean-Pierre Bart Inc. says that the colour chosen for the precast was directly related to its function within the overall design of the building. "The advantage of precast is that we can get any colour we want," says Bart, "and on this project, we worked very hard to get the colour just right. I used to use warmer colours, but because Le Vistal is a GREEN building – a LEED building – I wanted a very modern colour, and we came up with a cool grey, which is very nice as far as I’m concerned."

Bart says that particular attention was paid to the precast joints to ensure that the building envelope was sealed tightly for energy efficiency. "We designed the joints between the panels to be accessible from the inside," he says, "so that both the inside and outside caulking could be applied really well to keep the water out." Papineau adds, "One of the tricky things – because we wanted the pieces to be slender – is that we fabricated the precast for two floors at a time, so the windows, and where the joints happen, is pretty critical because of the anchors."

Alex Stamino, project manager for Magil Construction, says that in the erection phase, they selected punch panels to enable that assembly plan. "We would then erect it in phases of eight storeys – all on one face – at a time, and when we’d finish one drop, if you like, we’d move over to the other elevation and do another drop, and so on. We’d stop it at each lift; each eight floors, there would be a break allowing us to pour some more concrete floors, and we’d usually need a buffer of about four to eight floors before we could consider erecting the precast. It was very smooth because once we installed the first eight floors, which allowed time for the other trades – studs and windows – to go in."

In fact, because of the assembly challenge presented by the height of the building, Le Vistal has produced a lasting legacy for the precast industry. "We used a mobile crane for the first 10 or 11 floors, and then we used the tower crane when they were topping the project off with concrete," explains Bouchard. "We also developed a (proprietary) system where we were able to place the panels on the structure – using a special connection method we developed – in such a way as they were not in their final position on the structure at first, but by doing this, we only needed to use the tower crane for maybe three or four hours, put perhaps 20 panels in place very quickly and finalize the installation of those afterward without the use of the tower crane, which, of course helps to keep costs down."

Le Vistal has raised the bar for what can be done with sustainability in the construction of these types of buildings, which some estimate account for 35 percent of carbon dioxide emissions in North America, and precast clearly played a large part. Gewurz hopes other developers follow his lead. "One building is (environmentally) insignificant," he told The Gazette. "But if all buildings in this country go in this direction, you really achieve something."

Client: Proment Corporation
Principle Architect: Jean-Pierre Bart Inc
General Contractor: Magil Construction
Precast Concrete: Béton Préfabriqués du Lac Inc