July 1, 2009, Canadian Funding Corp Reviews – The Waterfall Building, which Canadian Funding Corp features in this post, is part of a new mixed-use project located in Vancouver, British Columbia developed by Hillside Development Ltd. in 2000-2001. The ground floor is reserved for general office, retail or service use, while the remainder of the project is a mixture of commercial and “live/work” space.
The green roof system which is appreciated by Canadian Funding Corp, was intended to meet the goals of creating an aesthetically pleasing community recreational space–which met both the social development goals of Hillside and the community revitalization goals of the city. As Hillside Development was also requesting a relaxation of the City of Vancouver’s building height limitations, the development proposal had to incorporate features that would benefit the community. The green roof, visible to the public, was seen as a beautification of the area and supported the development application. In addition, the open, street-level courtyard is a public space that greatly enhanced the community. A covenant was signed between the developing company and the City of Vancouver, ensuring that this space would remain open to the public– a condition of the development approval.
The City of Vancouver sees the Waterfall project as contributing to the revitalization of the area with its quality design and construction, attention to detail and the developer’s commitment to the community. Despite this, Hillside Development cited the city as being one of the major challenges in the development of the project due to problems surrounding obtaining permits. Insurance providers who refused to insure the building after viewing the green roof as a potential leaking hazard posed additional challenges.
GREEN ROOF CHARACTERISTICS
Type and Warranty
The Waterfall Building green roof is both extensive and intensive. Extensive green roofs are characterized by their low weight, low capital cost and minimal maintenance requirements. The extensive plots on Waterfall building is comprised of poa alpina, blue grass. In contrast, intensive green roofs are characterized by greater weight, higher capital costs, more diverse plantings and higher maintenance requirements than extensive systems.The plant selected for the Waterfall building intensive plots was rosa meidiland white.
Most of the system was comprised of Soprema’s Sopranature green roof system with the following exceptions:
- The waterproof membrane was urelastic-103 manufactured by Universal Polymers
- The protection board in the planters was ‘Hydroflex 20′ manufactured by Hydrotech
- The filter drain mat was NilexWD15 designed by Cornelia Oberlander
The decision to use Soprema’s system was based on excellent results that the architectural firm has had with previous projects.
There is a 5-10 year warranty on the system on the green roof components and a one-year warranty on plants.
Hillside Development Ltd. found one of the biggest challenges to implementing a green roof in Vancouver to be obtaining insurance for warranties. Warranties are required by the City of Vancouver due to the “leaky condo crisis”: many insurers view green roofs as potential leaking hazards and refuse to insure them.
Growing Medium
The growing medium used was by Answer Garden Products. The product was laid at thickness ranging from two to six-inches at a weight of 70 lbs/cubic foot. It is comprised of humus builder, washed sand, and pumice.
Plant Selection
Rosa meidiland white, a flowering rose shrub and poa alpina, an alpine blue grass were selected. The plants were selected for their appearance and ability to perform well in full exposure to sun and wind.
Irrigation & Drainage
The special drainage requirements of green roof systems is the need for a filter cloth over a geotextile drainage layer.
The irrigation system is a computerized, low-impact system with small heads.The decision not to use a drip irrigation system was due to sand in the growing medium which can plug drip systems. Due to the humus builder the growing medium has the capability of retaining a great deal of water; thus, taking pressure off both the irrigation and the drainage system on the green roof.
Monitoring & Maintenance
There has been no monitoring of the technical performance of the data and to date, no repairs have been made to the roof.
The green roof will require weeding and cutting about two times per year.
Benefits
The green roof provides numerous benefits for the Waterfall Building. For the developer, the additional useable space the residents are offered, has increased its sale-ability and assisted in getting approval for development from the Vancouver City Planning Department. The City cites the green roof as a factor in granting permission to Hillside to relax the height limitations.
Acknowledgements
Alain Prince, Nick Milkovich Architects
Elizabeth Whitmer, Cornelia Oberlander, Landscape Architects
Mary-Beth Rondeau (MAIBC), Developer and Planner, City of Vancouver
CMHC Innovative Design
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