Green Roofs for Healthy Cities (GRHC)

Green Roofs for Healthy Cities (GRHC) is a non-profit industry association for green roofs and green walls in North America. It describes itself as having worked to grow the green roof and wall industry since 1999. Its website is greenroofs.org.

Members include designers, landscape architects, roofing contractors, growers, manufacturers of green roof components, researchers and policy makers.

Activities

• Green Roof Professional (GRP) accreditation. GRHC created and manages the GRP credential, which covers the design, installation and maintenance of green roofs. Training for the credential is offered as a self-paced online course through its Living Architecture Academy.
• CitiesAlive conference. GRHC organises CitiesAlive, an annual conference on green roofs, walls and urban green infrastructure.
• Awards. It runs the Green Roof & Wall Awards of Excellence for outstanding projects, people and organisations.
• Policy. It promotes municipal policies that encourage or require green roofs, such as incentive programs and green roof bylaws in North American cities.

What a green roof is

A green (vegetated) roof is a roof covered with a growing medium and plants, placed over a waterproofing membrane and root barrier. Main types are:

• Extensive green roofs, with a thin, lightweight growing layer, often 50-150 mm (2-6 in), planted with hardy sedums and grasses and needing little maintenance;
• Intensive green roofs, with deeper soil that can support shrubs, trees and amenity spaces, but adding much more weight;
• Semi-intensive systems in between.

Benefits can include stormwater retention, reduced roof surface temperatures, habitat for pollinators and longer membrane life due to protection from ultraviolet light and temperature swings. Structural capacity, drainage, wind uplift and fire breaks must be addressed in design.

Related organisations

In Europe, national green roof associations work together through the European Federation of Green Roof and Green Wall Associations (EFB). German FLL guidelines are a widely used technical reference internationally. In Canada, the Roofing Contractors Association of British Columbia has introduced a warranty program specifically for green roofs.