Green is becoming the new white when it comes to Canadian roofs.

Everyone knows that a white, snow-covered roof is the mark of successful heat-retention and insulation. Canadian property owners intent on generating financial gain from energy-efficient commitments may be attracted to the green roof concept.

The City of Toronto, one of Canada's leading property owners, is transforming civic rooftops and will encourage developers of new flat-topped buildings to incorporate green roofs. The report "Toronto at the Crossroads: Shaping Our Future" states: "One of the greatest opportunities for greening the City is the promotion of 'green roofs' which involves layering contained soil and planting gardens on the flat roofs dominating the landscape of many districts in Toronto. Green roofs do much more than improve the view from downtown skyscrapers. They also:

• Absorb stormwater and reduce off-site flows;

• Absorb carbon dioxide and work against the greenhouse effect;

• Conserve energy for the building below them; and,

• Can be made into beautiful flower gardens or bountiful food gardens for occupants."

But don't just think "potted plants." This extension of the roof system includes a special water-proof and root-repellant membrane, a drainage system, filter cloth and a lightweight growing medium. Green roofs, well-established features on European buildings, may be installed as full-roof systems or created using contained modular, moveable units. Technologies fall into two categories:

1. Extensive green roofs are characterized by their low weight, low capital cost and minimal maintenance.

2. Intensive green roofs have a greater soil depth, usually more than 6 inches, and more plantings with higher maintenance requirements. i

This environmentally-friendly movement also carries a strong business draw. The mission of Green Roofs for Healthy Cities (GRHC) is to achieve the development of a multi-million dollar market for green roof products and services in cities throughout North America. The network, which consists of public and private organizations, was established in 1999 in response to a year-long research project for Canada Mortgage and Housing Corporation (CMHC) and Environment Canada. According to GRHC, "the current market environment fails to fully value the tangible public and private benefits of these technologies."

Green-roof installation expenses must be weighed against the extended life of the roof system and reduced heating and cooling costs for the building. Not at the "do-it-yourself" level yet, green roof design requires experienced experts like landscape architects to evaluate how elements such as the roof's slope, structural loading capacity and existing roofing materials affect the choice of technologies. Landscape design incorporates climate, maintenance and other practical considerations within a feasible budget.

GRHC's 2004 Awards of Excellence included a residential single-family home located on an island in the St. Lawrence River, east of Kingston, Ontario. The Island House has an award-winning extensive green roof system, which helps the building blend into its beautiful surroundings:

• The upper and lower roofs incorporate a Sopranature green roof system which covers a total of 1,700 square feet.

• The lower roof uses different species of sedum and the upper roof is a wildflower meadow incorporating local plants.

Green roof technology research and development is on a growth trend in B.C. where federal funding of up to C$600,000 over the next three years will support B.C. Institute of Technology's Centre for the Advancement of Green Roof Technology. Regarded as "Canada's premier polytechnic institution," BCIT's leadership role in advancing green roof technology should go beyond benefits to students and local manufacturers. Researchers continue to monitor the Centre's green roofs for suitability in BC's climate and to measure energy consumption reductions in the building. This testing of materials and systems should also increase consumer confidence and spread green roof usage.