Greenroofs  - Commercial / Industrial / Institutional
 

Green roofs can be integrated into a proposed or existing project to help meet stormwater management requirements.  Beyond stormwater management concerns, many green roofs in urban areas have been designed with multiple benefits in mind, such as aesthetic enhancement, improvements in air quality, and habitat re-creation. 
 

Toronto City Hall

In November of 2000 the Green Roof Infrastructure Demonstration Project was launched in order to showcase the benefits of green roofs in urban areas. The project consists of a public-private partnership between the member companies of Green Roofs for Healthy Cities, the City of Toronto, the Toronto Atmospheric Fund, the National Research Council's Institute for Research in Construction and Environment Canada. The goal of the demonstration project was to generate reliable technical data on green roof performance in areas such as energy efficiency, heating and cooling benefits, air quality improvement, stormwater retention, and the extension of roof membrane life span and plant survival in the Toronto climatic context. ¹

Green roof plot at Toronto City Hall
Green Roof Infrastructure Demonstration Project
(Source: Green Roofs for Healthy Cities)

Semi-extensive green roof plot at Toronto City Hall
Green Roof Infrastructure Demonstration Project
(Source: Green Roofs for Healthy Cities)

Components of the demonstration rooftop include a native butterfly and bird habitat, urban agricultural plots with perennials and annuals, two semi-intensive plots featuring a variety of flowering plants, shrubs and small trees, two extensive plots featuring a variety of sedum and alpine perennials and, species native to Black Oak Savannah, a native prairie ecosystem.

For more information on this project see http://www.peck.ca/grhcc/overviewdemo.htm, or please contact Steven Peck, Executive Director, Green Roofs for Healthy Cities through the same web site address.

Chicago City Hall

As a part of the EPA Urban Heat Island Initiative project a 38,800 square foot semi-extensive green roof was installed in April 2000 for the Chicago City Hall. This retrofit application, which cost more than a million dollars to design and install, was created as a demonstration project to showcase the benefits of green roofs in moderating summer temperatures within ultra-urban environments. The landscape design followed a formal garden plan as opposed to a meadow-like environment. The project included a wide range of roof landscape environments, from a 3.5-inch deep 'extensive' system to 24-inch deep 'intensive' landscape islands. Approximately 14,000 cubic feet of polystyrene will be used to create the illusion of a rolling terrain. A drip irrigation system fed partially by water collected from the adjacent penthouse roof, was also incorporated into the roof design. The project was completed in the summer of 2001 and will be monitored for plant survival as well as other environmental features such as stormwater management. ²
 

Chicago City Hall
Urban Heat Island Initiative project
(Source: Roofscapes, Inc.)

Fencing Academy of Philadelphia PA

An extensive 3000 square foot green rooftop with a meadow-like setting of perennial sedum varieties was installed on the Fencing Academy of Philadelphia in the spring of 1998.  The installation was a retrofit design with the performance objective being the restoration of the pre-development hydrology for the 2-year return-frequency storm. 

Fencing Academy of Philadelphia PA
Vegetated roof cover
(Source: Roofscapes, Inc.)

The vegetated cover has now reached a mature stage of development, creating a meadow-like setting of perennial Sedum varieties that had been selected to withstand the range of seasonal conditions typical of the Mid-Atlantic region without then need for irrigation or regular maintenance. The appearance of the roof changes with the seasons. In the spring fescue grass and sedge, along with allium, burnet and dianthus dominate species. During the summer and fall months flowering sedum varieties dominate.

The roof cover is only 3.4” thick, including the drain layer, and weighs less than 5 lb/sf when dry, with a maximum saturated weight of under 17 lb/sf. The moisture content of the soil media at field capacity is 45% (volume), and the saturated infiltration capacity is 3.5 in/hr. The Philadelphia Fencing Academy green roof has been continuously monitored for temperature readings since its completion and compared with an adjacent unvegetated roof cover. During the spring and summer, the daily variation in temperature on the bare roof ranges up to 90 degrees F (50 degrees C), while the variation under the vegetative cover is only 18 degrees F (10 degrees C), or less. ² The green roof is growing in nicely and has met its stormwater management design requirements.

Fencing Academy of Philadelphia
Vegetated roof cover temperature data
(Source: Roofscapes, Inc.)

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