When the province of Alberta, Canada, decommissioned and demolished the Calgary General Hospital in October 1998, the city of Calgary was presented with a unique opportunity. Overlooking downtown Calgary, the land in the Bridgeland Riverside neighborhood—known to residents as “The Bridges”—was very valuable. With many development options before them, Calgary made the decision to create a green, pedestrian-friendly, transit-oriented urban community on the site of the old hospital.
Developers were invited to submit proposals for residential, retail and mixed-use parcels. A checklist of green strategies was part of the city’s requirements for development. Ottawa-based Windmill Development Group teamed up with Vancouver, British Columbia, Canada-based Busby Perkins+Will to submit a proposal for a townhouse project that would far exceed the city’s green expectations. The Vento Residences were accepted for development and, when completed in 2006, earned a LEED Canada for New Construction Platinum certification from the Ottawa-based Canada Green Building Council. The project also earned CaGBC’s Durable Building Credit as part of this certification. (To learn more about Canada’s Durable Building Credit, see “deep green” in eco-structure’s May issue, page 62.)
ENERGY WISE
Vento Residences’ central residential courtyard terrace is surrounded by 20, 2-story townhouse suites situated above a ground-floor level of retail and commercial space, as well as two affordable-housing units. Small, local businesses, such as a café and wine shop, populate the first level. Along with being green, the suites also needed to be cost-effective and attractive to buyers in a very crowded market. “There were probably about 200 to 300 units being constructed at the same time as Vento, all within a stone’s throw of each other,” recalls Robert Drew, associate principal at Busby Perkins+Will. “So the old ‘location, location, location’ adage didn’t really apply here.”
Many of the development’s green features would prove to be attractive to potential buyers. In terms of energy efficiency, Vento Residences is performing at a level 44.4 percent better than the Ottawa-based National Research Council of Canada’s Model National Energy Code of Canada for Buildings 1997. “We wanted to be able to market this building as being energy wise,” Drew says. “People purchasing a suite here could expect to have lower utility rates than the market housing just across the street.”
The building envelope is central to the energy strategy of the residences. The wall system is insulated to achieve a rating of R-24. “The building is very well insulated. We were trying to avoid leakycondo syndrome,” Drew explains. “This is partially resolved by best-practices detailing and by providing a ventilated cavity immediately behind the cladding system. The ventilated cavity facilitates quicker drying times for the cladding system and reduces the opportunity for mold growth in the envelope.
Heat-recovery units draw heat out of the exhaust air from the kitchen and bathroom. This heat is normally exhausted to the exterior, but in the Vento Residences, the heat is used to preheat incoming air. Even in the cold Calgary winters, this allows a healthy air exchange while using considerably less energy to maintain room temperature than a typical furnace warming below-freezing air from outside.
The building has an east-west orientation with a southern exposure on the courtyard side. All the key living spaces and private patios are located off the courtyard, which helps maximize the available daylight in the suites. To avoid unwanted solar heat gain in the summer months, the team performed solar modeling and designed the upper floor balconies to act as sunshades to the living-room windows below. Although the summer sun is shaded by the balconies, the winter sun radiates to the floor and heats the interior spaces of the living rooms. With an R-value of 40, the roof system is another important part of Vento Residences’ envelope strategy. The white, thermoplastic polyolefin roof system also helps reduce the urban-heat-island effect. Trees, shrubs and gardens provide an urban oasis on the terrace and ground levels below. “We wanted to develop an ecosystem that more closely approximates the natural system that existed prior to urban development,” Drew asserts. “In addition to selecting materials that maintain cooler site temperatures, we also provided a significant amount of flora to ensure a healthy ecosystem could develop on the site.”
REUSE AND RECYCLE
Water and waste management are becoming critical considerations in the Calgary market, so the design team for Vento Residences took ambitious approaches to both. It is one of the first projects in Alberta to incorporate greywater recycling. Rainfall is collected and goes to a cistern where it is filtered, treated and later used for toilet flushing and irrigation. Three common taps are hooked into the rainwater cistern, allowing residents to water their plants without drawing from the city’s reservoir.
At the time of design and construction, the Alberta Building Code did not allow anything other than potable water to be used for toilet flushing, but special consideration from the city of Calgary and the Calgary Health Region made it possible to use greywater on this project. However, it did take some effort to convince the city to allow this innovation.
“The provinces develop the building codes and the cities are generally required to enforce those codes,” Drew explains. “In almost all the jurisdictions in Canada, water is defined as either blackwater, which is sewage, or potable water, which is treated. There was no definition of greywater in the Alberta Building Code. Fortunately, the city of Calgary proved to be very forward-looking and permitted greywater recycling for toilet and irrigation use. Recently, the [Mississauga, Ontario, Canada-based] Canadian Standards Association issued a national standard regulating greywater. It is anticipated that future revisions to building codes will permit greywater recycling.”
In the area of construction-waste management, the project was able to recycle more than half its potential waste and divert it from landfills. “This was a great achievement, especially in Alberta, which is not as developed as some of the other areas in Canada,” Drew says. “The contractor worked very hard to find facilities equipped to recycle construction waste. For example, a gypsum recycling plant had become overwhelmed with waste drywall and had to temporarily postpone accepting it. This coincided with Vento’s construction. Rather than diverting the waste drywall to the landfill, the contractor elected to store the drywall until the plant was accepting the product again. This is an excellent example of how important it is to have a contractor who understands and shares the environmental goals of the project.”
HEALTHY ENVIRONMENT
Another critical goal of the development was to create and promote a healthy living environment. Great care was given to foster a comfortable, healthy environment inside and outside the suites. The products used on the interior are all low- and no-VOC to minimize harmful offgassing.
“When you walk through the suites, even when they were just completed and the windows were closed, you couldn’t tell it was a brand new home,” Drew recalls. “That ‘new car’ smell we all think of as being good is not. If you walk into someone’s house and they just installed new carpet, the smell is very unhealthy to breathe. We wanted to ensure that residents with asthma or chemical sensitivities could live comfortably in their suites.”
Radiant-floor heating generates a comfortable temperature in the winter months. “The system provides a heat source where people want it most, which is the surface they’re walking on,” Drew says. “That heat then radiates upward, making it warm at the floor and slightly cooler as you go up. If you look at the profile, that is exactly the way we like temperatures to be. We actually like our heads to be in a slightly cooler zone, but we want our feet to be warm.”
All 20 units sold out prior to the completion of construction. Drew attributes much of the project’s success to planning and integrated design. “We engaged all the stakeholders at a very early stage,” he says. “Even before we knew what this building would look like, we were talking to the city and discussing regulation challenges we would face surrounding the greywater system, for example. We had the city, province, all the engineers and even community representatives at the table. There were probably up to 40 people at the first design charrette.”
This approach allowed the team to address any issues before they became real problems. For example, as a result of the early dialogue between the developer and municipal government, each party knew what to expect from the other. The city understood the innovation the project would bring and the developer understood the permitting challenges and other steps it would face.
“Considering what this building became, it actually went incredibly smoothly,” Drew remarks. “Even though it had to open the eyes of a lot of people, we were able to engage all the stakeholders, including the city and community, from the beginning. As a result of that, there were no surprises.”
