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Green roof technology helps lower the cooling costs of a building by decreasing the temperature of the roof and the air-intake around AC units. A 2003 study by the National Research Council of Canada found that green roofs can reduce summer energy demand by up to 75% in a single story building.
• The green roof on the Ford Truck Plant in Dearborn, Michigan reduced the building's annual energy consumption by 7% (Earth Pledge, 2005).
• Chicago City Hall installed a 22,000 sq ft semi-intensive green roof and updated their HVAC system to reduce their monthly energy bill by $10,000 (Nolan, 2009).
• The GAP, Inc. Headquarters in San Bruno, CA installed a 69,000 sq ft extensive green roof and reduced their annual energy consumption by an estimated $25,000, an 11 year ROI (Cities, 2006).
Typical waterproof membranes need to be replaced every 10 to 20 years. With the protection of a green roof, membranes won't need replacing for 40-80 years. Some green roofs in Europe are over 100 years old and still waterproof. This longevity is due to a green roof's ability to protect the membrane from:
- UV rays, electromagnetic radiation, and falling objects.
- Extreme temperature fluctuations in summer and winter.
• In the summer, a black roof will fluctuate between 150ºF and 70ºF in 12 hours. Green roofs maintain a consistent temperature of around 80ºF (Kingsbury, 2008).
Green roofs transform an underutilized, barren landscape into an urban oasis. They also increase the property value of apartment buildings, homes, and commercial structures.
• GIS studies have shown that real estate within 800 feet of green space increases in value by up to 22% (Nicholls, 2004).
Roofs provide a great space for urban farming, a rising movement around the world.
• The Fairmont Waterfront Hotel in Vancouver, BC produces $25,000 to $30,000 worth of herbs and produce annually (Kingsbury, 2008).
• Refer to our Portfolio page to see various rooftop farm projects we've built.
Hospitals with open green spaces record patient check-out times 2.5 days earlier then hospitals without green spaces.
• The 10,000 sf green roof on the Schwab Rehabilitation Hospital in Chicago also serves as a rooftop park and garden for horticultural therapy, a process in which plants and gardening activities are employed to improve body, spirit and mind (Green Roofs for Healthy Cities, 2005).
• A 1988 study demonstrated that the availability of a natural view can be instrumental in the alleviation of daily stress, physical ailments, a decrease in number of sick days and an increase in worker satisfaction and productivity (Kaplan, 2001).
• Worker productivity in green office buildings increases by 2 to 16% (Peck, 2008).
Green roofs can help reduce external noise pollution by 10 to 50 decibels depending on the thickness of the system.
• The Gap Headquarters, located near the San Francisco International Airport, built a green roof to reduce noise pollution by 50 decibels (Kingsbury, 2008).
Some plants are more fire resistant then others. Succulents such as sedums contain water and are difficult to burn, making ideal plants for green roofs. Green roofs therefore act as a fire retardant on a rooftop.
• A green roof has a burning heat load of 3 kWh/m² while a 3-ply bitumen roofing system, a common membrane type, has a burning heat load of 50 kWh/m². This means that the heat from a fire on a green roof will be 1/16th the heat from a bitumen system (M Koehler, 2003).
Solar panels and green roofs are a perfect match. When mounted on green roofs, solar panels generate up to fifteen percent more energy than those on black roofs because they maintain a more optimal operating temperature of 77ºF.
Green Roofs recieve credits for various categories including sustainable sites, water efficiency, energy and atmosphere, and innovation and design process:
Heat Island Reduction
Water Efficiency Landscaping
ENERGY & ATMOSPHERE
Optimize Energy Performance
INNOVATION & DESIGN PROCESS
Green roofs reduce and delay stormwater runoff, helping to mitigate combine sewage overflows (CSOs), which result when storm water floods a city's sewer system and discharges raw sewage into the local watershed. Green roofs also filter pollutants from rainwater, roofing materials, and atmospheric deposition.
• Extensive green roofs can retain an average of 75% annual rainfall and delay runoff by 3 to 4 hours (Susan K. Weiler, 2009).
• A study conducted by Environment Canada found that if Toronto covered 6% of available roof space with green roofs, it could retain 127 million cubic feet of rain water per year. The storage tank needed to hold the same amount of rainwater would cost $60 million while the green roofs needed would cost $45 million.
• The 10.4 acre green roof on the Ford Dearborn Truck Plant retains approximately 4 million gallons of rainwater each year (XeroFlor).
• The 18,000 square foot green roof atop Radio City Music Hall will prevent approximately 566,000 gallons of water from entering New York City's sewage system (environmentalleader.com).
The average food product in the US travels 1,500 miles before reaching a consumer, increasing food costs and CO2 emissions (CUESA). Food roofs in urban communities bring high-quality fruits, vegetables, and herbs to densely populated areas. They promote healthy eating, create jobs, and allow for a more sustainable, seasonal food system. Please refer to our Portfolio page to view our Food Roof projects.
Air temperatures in urban areas have increased by 2ºF per decade over the last 50 years and are now 7 to 11ºF higher than in the surrounding undeveloped areas. Green roofs can alleviate the Urban Heat Island effect by covering black rooftops, one of the hottest factors in the urban environment, with cool, green surfaces.
Black roofs can reach temperatures of 150ºF while green roofs rarely exceed 86ºF (Kingsbury, 2008).
Green roofs absorb airborne particles and carbon dioxide while releasing oxygen, effectively filtering and cleaning our atmosphere. By reducing the ambient summer temperature around a building, less energy is needed for air conditioning, and thus produce fewer CO2 emissions.
• The green roof on the Ford Truck Plant in Dearborn Michigan is predicted to improve the air quality around the building by 40% by absorbing dust and breaking down hydrocarbons (Earth Pledge, 2005).
Green roofs keep waste out of landfills by using recycled materials and by extending the life of a roof by two to three times its average life span.
Green roofs replace ecosystems that have been displaced by city infrastructure. High-rise build spaces create habitats for various species and insects, particularly birds traveling north and south.
• The 2.5 acre green roof on the California Academy of Science consists of native vegetation designed as a habitat for indigenous species, including the threatened Bay Checkerspot butterfly (California Academy of Science).
• Mexico City’s nonprofit organization CICEANA cultivates 25 endangered native plants on its roof (Earth Pledge, 2005).