Green Roofs - Living Architecture Monitor - Summer 2013 - (Page 12)

RESEARCH ON THE ROOF WITH… THE BUSINESS CASE FOR INVESTING IN GREEN ROOFS IN PORTLAND SUMMARIZING A COST BENEFIT EVALUATION OF ECOROOFS IN PORTLAND, OREGON BY: ELERI DAVIES W orking in conjunction with the Bureau of Environmental Services (BES), the City of Portland conducted a cost beneﬁt evaluation of ecoroofs speciﬁcally designed for Portland, Oregon. The evaluation, prepared by ECONorthwest and David Evans and Associates, looked at the economic beneﬁts of green roofs on stormwater management and infrastructure, energy, climate, habitat, amenity value and building development. The evaluation drew on data from over 70 articles and reports, several of which were speciﬁc to the City of Portland. Since no uniform standards exist for ecoroof assessments, a basic ecoroof deﬁned by the BES was used. By BES standards, a basic ecoroof includes a moisture mat, protection board, 5-inch growing medium, gravel drainage, simple irrigation system and LIVING ARCHITECTURE MONITOR / SUMMER 2013 / 12 plant palette of sedums, grasses and wildﬂowers. A 5-storey commercial building with a 40,000 square-foot (sf) roof was used to represent ecoroof implementation on a multi-block basis—the typical Portland block is 200-ft by 200-ft. While the evaluation provides economic data for ecoroofs, it should be noted that the ecoroofs were designed speciﬁcally for Portland’s climate; therefore the results from the study are only applicable to areas that share similar climatic characteristics. As a result, cost beneﬁt evaluations ideally should be considered on a case-by-case basis. STORMWATER MANAGEMENT AND INFRASTRUCTURE BENEFITS The City of Portland found green roofs to be a highly effective best management practice at reducing stormwater volume ABOVE: THE AWARD OF EXCELLENCE WINNING LOUISA GREEN ROOF IN PORTLAND Image provided by: Walker Macy Landscape Architects and peak ﬂow. Considering Portland’s annual rainfall of 37-inches, a conventional roof (on average) will have a 95 percent runoff. This means that a 40,000 sf roof will annually produce 877,000 gallons of stormwater; where an ecoroof will produce 406,000 gallons—a 56 percent reduction. This translates to a 56 percent reduction in the one-time costs associated with managing stormwater—$60,700 savings from the $108,400 conventional roof cost. As of 2008, Portland spent $95/1,000 sf to manage stormwater from public and private sources. Therefore for a conventional 40,000 sf roof, the operation and maintenance (O&M) costs would be $3,800. The READ THIS ISSUE ONLINE AT WWW.LIVINGARCHITECTUREMONITOR.COM http://WWW.LIVINGARCHITECTUREMONITOR.COM

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2013

Green Roofs - Living Architecture Monitor - Summer 2013
Contents
From the Founder
Green Roof Installation Raises Value of Boston Apartment by $2.4 Million
Green Roof Industry Grows by 24 Percent in 2012 & Washington Dc Is #1
Burgeoning Green Roofs and Green Walls Market to Be Worth $7.7 Billion in 2017
Green Roofs Designated as Certified Wildlife Habitats by National Wildlife Federation
On the Roof With … Art Rosenfeld
Estimating Green Roof Benefits
Mind Mapping the Business Case
The Business Case for Investing in Green Roofs in Portland
CITIESALIVE San Francisco Preview
Policy and Standards
Leadership – for the Sake of the Client and the Environment:
Plant – Profitable Green Roof Plants
Project – It Takes a Village: YMCA
Project – Was It Worth It?
New Corporate Members
Professional Calendar
New and Improved Green Roof Training
Submit a Project to the 2013 Awards of Excellence
Journal of Living Architecture Call for Papers
Great Community Resiliency Project Contest
GRHC Buyers Guide
The Case for Green Façades

Green Roofs - Living Architecture Monitor - Summer 2013