Sprouting up

Green roofs are increasingly part of the design and construction of new buildings

The concept of the green roof has been around for a while, but Alberta hasn't been quick to embrace it. That's not surprising-winters here are cold, and successfully growing ground-level gardens can be a challenge with a short growing season. But recently, a number of green roofs have been springing up in construction projects around the province, many of them in the Edmonton area, suggesting contractors are increasingly comfortable with incorporating these unique green spaces into their projects.

The Enjoy Centre in St. Albert, Alta., is one example. The 242,000-square-foot facility features four rooftop modules, each encapsulating its own little garden.

The green roof component is the work of the Northern Alberta Institute of technology (NAIT)'s School of Sustainable Building and Environmental Management.

"Many building owners in central Alberta, including the owners of the Enjoy Centre, have an interest in green roofs, and we wanted more information on the benefits of green roofs in north-central Alberta," says Leonie Nadeau, a retired senior faculty researcher who remains involved in the project.


Nadeau explains that the roof will provide some answers specifically for the region. "We have all kinds of information from the warmer, humid areas of the U.S. and Europe. We don't have as much info for dryer, colder environments like we have in Alberta."

NAIT has installed roofing evaluation modules designed at the British Columbia Institute of Technology. Sensors in the roof allow the team to collect information about things like heat distribution and loss, and water retention and drainage.

The benefits could extend to the environment and to building owners. For example, in St. Albert, when you buy a piece of land, you are required to buy enough for the creation of a retention pond. But what if a green roof will retain enough water so that the water can drain off slowly? "That could actually change the way the city does business," she says.

Nadeau, who has been involved with green roofs for the past four years, says that she believes the technology and knowledge for creating effective, sustainable green roofs in Alberta already exists. What's needed now is to fine-tune what is known for different climates.

Mike Widdifield, project manager, PCL Construction Management Inc. in Edmonton, agrees that the technology and know-how are in place for the successful incorporation of green roofs. Widdifield is in charge of the construction of PCL's $24-million, 82,000-square-foot headquarters expansion at the PCL Business Park in Edmonton. An impressive 40 per cent of the total roof area will be green.

"PCL has committed to sustainable design and construction, starting with the Centennial Learning Centre [completed in Edmonton in 2006] being a Leadership in Energy and Environmental Design building. It's pretty important for us to maintain that," says Widdifield. "We're also in a pretty heavy industrial area, and this adds aesthetics for the occupants and makes a more pleasurable space for them."

Widdifield says that green roofs are becoming easier to incorporate into buildings because more designers and contractors have experience with them. In addition, the products being developed using green-roof knowledge and technology are making for more efficient installation and maintenance.

PCL is using a relatively new product on the 4,800-square-foot green roof that will top the two-storey component of the building. It's a lightweight, low-maintenance system of modular, pre-manufactured units that come complete with drainage trays, the growing medium and vegetation.

"We used that recently on a PCL-built project in Edmonton," says Widdifield. "Feedback from our team on that project led us to use that product here."

Interestingly, 5,800-square-feet of the green roof space on PCL's new building will actually be at ground level. Because the basement has a different footprint than the three-storey and two-storey components of the building, two courtyards that appear to be normal green space will, in fact, be roofs.

Called intensive green roofs because they have a deeper growing medium and higher-maintenance vegetation, these roofs will feature grasses, perennials, shrubs and even trees.

With soil a metre deep in some places, it's important that the roofs are constructed properly. That's something Widdifield says industry needs to maintain focus on even as it becomes more comfortable with green roofs.


"The more experience everybody gets doing the construction process for green roofs, the easier it is going to get. But we still have to make sure that we pay special attention to the details and the construction so that the system works, because it's a main component of the building envelope," says Widdifield.

Environmental consciousness is the driver behind the green roof movement, but owners are realizing that they aren't right for every building. "ATB Financial is trying different sustainable options in our facilities," says John Swarbrick, vice-president, central region, ATB.

The financial institution's new branch in Sylvan Lake has an approximately 1,700-square-foot green roof on its 3,800-square-foot roof, and it has successfully survived its first winter. It's a pilot project that ATB is watching closely to determine whether or not to include rooftop gardens in future facilities, but it won't necessarily result in a green roof on every new branch.

"I believe that [ATB] is leaning toward it in the next branches, depending on the location of the branch and whether it makes sense with the design of the branch," says Swarbrick.

He offers the example of a branch in Red Deer, Alta., that wasn't a good fit for a green roof because it was designed with an angled roof. At that location, ATB chose to capture used water in underground reservoirs for exterior watering as part of its commitment to sustainability.

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