Case Study:
George and Kathy Dembroski Centre for Horticulture

Green Thumb: A New, Light-Filled Entrance and Addition Establishes a Botanical Garden's Reputation.

By Nadav Malin

To Toronto residents who walk into the Toronto Botanical Garden’s new facilities,  it seems obvious now but when David Sisam, principal of Montgomery Sisam Architects, suggested eliminating a series of entrance ramps and converting what was a split level design into a simple, grade-level opening, it was a revelation. Previously, visitors to the facility walked up a berm from the parking area and entered the facility between the ground floor and second floor. Inside, large ramps led up or down. By removing both the berm and the ramps, Sisam found new space and simplified the layout. That intervention structured the design of the renovation and addition to two buildings in an expansion that transformed the sleepy Civic Garden Centre into a major urban botanical garden. The existing site conditions included administrative offices in a 1964 wood-and-stone building designed by Raymond Moriyama, connected to a larger conference and meeting facility built in 1976 and designed by Jerome Markson. These buildings, as venerable as they were, could not adequately satisfy the Centre’s ambitions for expanding its programming. The design team’s solution was to reconfigure the entrance lobby of the Markson building, removing problematic south-facing sloped glazing, and to add a new 3,800-square-foot retail wing. The addition, which sports a sloped, vegetated roof, clear glazing at ground level, and translucent panels above, helps define several new outdoor spaces. “The design is all about providing a sense of the connection between the indoors and outdoors. We joked that usually architects take the lead on projects like this, but here the landscape architects took charge because we all acknowledged that the gardens are the most important part,” notes Sisam.

Owned by the City of Toronto, the facilities are located at one end of Edwards Park, a large estate-turned-public-park that is part of a greenway linking open spaces throughout the city. A $350,000 challenge grant from the Kresge Foundation launched the organization’s fundraising campaign. Kresge offered an additional $150,000 if the project was LEED-certified, which executive director Margo Welsh says was an easy decision for the ecologically oriented group. With a total budget of nearly $7.6 million dollars, $3.3 million went to the renovation and addition. The remainder covered the landscape work, design fees, and other soft costs.

Two firms, PMA Landscape Architects and Thomas Sparling, collaborated to create a landscape surrounding the new building that includes 14 different gardens on less than four acres of property, according to PMA’s Jim Melvin. With the exception of the entry garden, which was commissioned by the Garden Club of Toronto, the two firms designed all the gardens and walkways on the site. While some of the gardens feature exotic plants, they were installed using only organic soils and amendments. The designers focused on utilizing material from the site and working the reuse of demolished material into their design. “We inventoried all the material before demolition started, so we knew exactly what we had to work with,” Melvin says, adding that “there was a bit of a battle between us and the architect as to who would get the better stone.”

The site sports two significant water features, both of which re-circulate water internally for a week before draining to underground storage tanks for irrigation use. By replacing the water weekly, the Botanical Garden avoids having to add chemicals, and the water doesn’t concentrate to the point where mineral deposits mar the surfaces, according to Melvin. The municipal water used to replenish the water features is the only use of potable water in the landscape, as all the irrigation is supplied from reclaimed water. In addition to the water features, roof runoff and condensation from the air conditioners feed irrigation tanks. Channels lead stormwater from the hardscape areas to underground infiltration pipes, where it irrigates deep-rooted plants before percolating into the soil. Runoff from the parking area goes to city drains, however. “When the parking lot gets redone, I hope they will use a permeable paver,” suggests Melvin.

Both the addition and the renovated space are infused with daylight that, together with direct views, helps bridge the exterior landscape and the interior spaces. “During the day, very rarely are lights on inside,” says Sisam. Environmental design and energy consultants Enermodal Engineering supported that work with energy and daylight modeling in software program Ecotect. “This gave us a very quick analysis and understanding of what was going to happen in the spaces,” says Enermodal’s Braden Kurczak. Supported by the simulations, Kurczak was able to convince the designers to use an opaque wall surface up to 18 inches from the floor. “The architects were all about having floor-to-ceiling glass, but there’s not much benefit in terms of light from any glazing below your knees,” Kurczak notes. The effect of this change on the building’s thermal performance was not huge, but it was one of many little things that added up to make a big difference, according to Kurczak.

In addition to the sill, the clear glass on the south side of the retail space in the new building is shaded by a trellis, while the translucent glazing above is fritted to reduce solar gain and glare from direct sun. Other energy-saving features of the project include efficient and well-distributed lighting fixtures, demand-controlled ventilation, and, for the new retail area, an enthalpy wheel providing energy-recovery in the ventilation air. The firm RS&G Commissioning reviewed plans and tested the installation to ensure that it operates as intended.

As construction manager, Rick Gosine of The Dalton Company served as liaison between the design and construction teams and the commissioning agent. Dalton also participated in the design process from the beginning, providing cost estimates on the various design alternatives. “When the design was exceeding our price expectations, we would come up with a plan to bring it back on budget,” Gosine says. Kurczak credits Dalton with coming up with an inexpensive solution for erosion control by putting silt fencing right up against the base of the eight-foot plywood hoarding wall that surrounded the construction site. Kuczak notes that the usual approach, using stand-alone silt fencing, would have required digging up paving in the parking lot.

For the purposes of the LEED submission, the scope of the project was limited to the 3,800-square-foot addition and a 4,300-square-foot area of substantial renovation, according to Kurzcak. The predicted 26 percent energy cost savings were enough to earn three energy optimization points in a renovation project, but only one in new construction. Given its nearly even split of new construction and renovation, the project earned two points.

Only minor steps were taken to improve the energy efficiency of the remaining 28,200 square feet of the existing building, so the facility’s overall energy use remains high. “Mechanical and electrical systems really do need upgrading in the existing buildings,” acknowledges Sisam. “When we were doing renovations, we found that we had to do more upgrading than we expected, because every time we opened something up it would fall apart,” he says. Welsh points out that it’s harder to raise money for improvements to existing facilities than for a new building. “We would like to have had more money to make greater improvements in the old buildings,” she says.

The ongoing need to address the older buildings aside, Welsh is thrilled with the project. “The building is beautiful, and the fact that it is certified LEED Silver excites people,” she says. Welsh is especially pleased that many city departments are choosing to hold meetings in the renovated facility, giving them a first-hand experience of a successful LEED project. The project demonstrates that “you can have something that is that great to be in, looks great, and is environmentally responsible,” she says.