In North America, Chicago is leading a number of cities who have chosen to pioneer green roof development with high profile greening programmes, including Portland, Oregon, Seattle, Washington, and Toronto.
Flood risk management has been a driver, though the main stimulus in the majority of North American cases is the attempt to reduce the pollution of rivers and water courses that results from run-off in the high rainfall climate of the north-west coast.
Toronto
Toronto suffers from significant urban heat island effects, which see summer temperatures in the city centre reach dangerous and uncomfortable levels. The city sees green roofs as a key tool in combating this phenomenon as they significantly reduce the amount of heat reflected off a roof surface, and also reduce the amount of heat leaving a building.
As a consequence green roofs are supported through various initiatives and policy objectives, which include:
- where feasible and practical, green roofs with a coverage of 50% – 75% of the building footprint be constructed on all new City-owned buildings;
- where feasible and practical, green roofs be installed on existing City owned buildings, when roofs are due to be replaced.
New York
Green roofs have been identified as a Best Management Practice in New York’s Water Quality Initiatives. This technology is named in Initiative 9:
Provide Incentives for Green Roofs as a part of a larger mandate to expand, track, and analyze new Best Management Practices. Since 2007, the City has supported the installation of extensive green roofs by enacting a property tax abatement to off-set 35% of the installation cost of a project.
This pilot will end in 2012, when it will be reassessed for extension and inclusion of other technologies. In 2007 the City also started developing four residential and two commercial pilots to analyze the potential cumulative benefits of green roofs on the city’s combined sewer system. A Green Roof Policy Task Force has also been established to:
- educate and engage potential stakeholders
- engage many stakeholders to map out the nature of the market into which green roofs would be incorporated
- develop a framework for the incorporation of green roofs into building practices.
Green Roofs are not a new idea in New York – it is home to one of the earliest roof gardens in North America – the series of green roofs on the Rockefeller Centre dating from 1936. Currently, the largest green roof installation in the city is on Silvercup Studios in Long Island City, Queens, measuring 2,800m2.
Portland, Oregon
Portland City has internal green building consultants to assist City buildings in meeting the following policy objectives:
- All new City-owned buildings are required to be built with a green roof that covers at least 70% of the roof. The remaining roof area must be covered with Energy Star rated roofing material.
- When practical, all roof replacements must also include a green roof.
It also offers a 35% reduction in storm water management charges and has an “Ecoroof Initiative” to raise awareness.
More than 20 years ago the city added a floor area ratio (FAR) bonus to its building code whereby builders could get permission to build extra square footage by employing favoured practices. Green roofs were eventually classified as a favoured practice in the 1990’s. One example cited is that a developer who installed 4,000 sq ft of green roof at a cost of $60,000 received permission to build an extra 12,000 sq ft of building density. This equated to six extra condo units, then selling for $395,000 each, a total of
$2,370,000.
As a result of such incentives, there are currently around 16,000m2 of green roofs in Portland.
Chicago
The City of Chicago also grants a density bonus option to developers whose buildings have a minimum vegetative coverage on the roof of 50% or 160m2 (whichever is greater), usually in the form of a green roof. Roofs are required to achieve a minimum solar reflection (albedo) of 25% – often met through the use of green roofs.
In addition, planning applications that include a green roof are fast tracked via a dedicated team of planners, cutting the application processing time by 66%.
In 2007 there were in excess of 300 green roofs totalling more than 278,000m2.
download full PDF report Greater Manchester Green roof feasibility report May 2009
****
Introductory manual for greening roofs in Canada
5 standout species for extensive green roofs
Green Roofs an overview
Green Roofs: Urban Heat Island Effect
Eco news / Environmental Health News
WORLDWIDE
ECO DESIGN
The site does not provide medical or legal advice. This website is for information purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read on this Web site. If you need legal advice for your specific problem, you should consult a licensed attorney in your area. Arch1design is not responsible for the content of external internet sites which link to this site or which are linked from it.
****
Heroin and Cornflakes ©2008 www.arch1design.com
