Green Roofs - Living Architecture Monitor - Spring 2012 - (Page 8)

ON THE ROOF WITH… ment. But it’s also important that appropriate policies are in place to promote and, in some cases, require the use of green infrastructure, such as EPA’s stormwater rulemaking, discussed below. what are your views on green roof infrastructure as a stormwater management tool? A: Because of their ability to absorb and delay rainfall runoff, green roofs can vastly reduce the quantity of stormwater runoff and of pollutants that flow to local rivers, lakes, or the ocean, making them an excellent tool for stormwater management at new development, redevelopment, or even retrofit sites. In fact, a green roof with only a three to four inch deep layer of growing media can generally absorb between one-half to one inch of rainfall from a storm event, keeping that volume of runoff from ever picking up pollutants and carrying them into storm drains, or from contributing to combined sewer overflow (“CSO”) events. For larger storms or back-to-back storm events a green roof can significantly delay the release of runoff even after the green roof becomes saturated and no longer retains water, reducing peak flows and flood events. Overall, it’s been estimated that extensive green roofs (typically a simple, light weight installation with 4-6 inches of growing media and a covering of hearty, drought tolerant vegetation) can retain between 40 to 80 percent of the total annual rain falling over them, meaning that substantial opportunity exists to reduce stormwater runoff across an entire city with widespread installation. Green roofs provide a range of other benefits, such as cleaner air, reduced energy needs for heating and cooling, reduced urban heat island effects, and longer lifespan of a roof surface, making them an ideal choice for investment. In figure 2-1: Green Infrastructure benefits and practices, green roofs come in at second with the highest amounts of yes under “stormwater runoff” and “improves community livability”. The Cty of Toronto passed a bylaw in 2009 requiring that most new development incorporate a green roof. The size of the green roof is dependent on the roof and gross floor area of building. what is your take on other cities adopting bylaws of this nature with models like Toronto and figures such as the aforementioned present? A: Urban stormwater runoff is one of the leading causes of surface water pollution across our country (and in cities such as Toronto), so it is encouraging to see cities adopting policies and ordinances that require the use of green infrastructure practices like green roofs, or that more broadly require use of practices that infiltrate, evaporate, or capture rainwater water for reuse in order to retain a certain volume of stormwater runoff on-site. These practices can effectively mimic natural hydrologic processes, reducing pollution and in some cases increasing local water supplies. Moreover, requiring TABLE ES-1: “EMERALD CITIES,” LISTED DARKEST TO LIGHTEST BY THE NUMBER OF KEY GREEN INFRASTRUCTURE ACTIONS TAKEN Requirement to use GI to reduce some portion of the exist ing impervious surfaces Guidance or other afﬁrmative assistance to accomplish GI within city City Philadelphia, PA Milwaukee, WI New York, NY Portland, OR Syracuse, NY Washington, D.C. Aurora, IL Toronto, Ontario, Canada Chicago, IL Kansas City, MO Nashville, TN Seattle, WA Pittsburgh, PA Rouge River Watershed, MI Long-term green infrastructure (GI) plan Retention standard Incentives for private-party actions Dedicated funding source for GI LIVING ARCHITECTURE MONITOR / SPRING 2012 / 8

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Spring 2012

Green Roofs - Living Architecture Monitor - Spring 2012
Contents
From the Founder
Seen & Heard
Bookshelf
Special Thanks
On the Roof With…
Innovation
Urban Agriculture Summit in Toronto August 15th – 18th
Citiesalive in Chicago Oct 17th – 19th
Policy and Standards
We Asked Experts Their Opinions on Modular or Loose Laid Green Roof Systems, Check Out What They Said
I Guess Size Really Does Matter! — Growing Media Insights
Eleanor Mckinney Taking Austin by the Horns
New Industry Products
Green Roof Falls Flat in New York City
Green Roofing Leader Shows Industry What They’re Made Of! Tremco Incorporated
Plant Profile
New GRP’s
Professional Calendar
New Corporate Members
GRHC Buyers Guide
On Spec

Green Roofs - Living Architecture Monitor - Spring 2012