July 2006 Guest Feature

Green Roof Industry Meets in Boston for Biggest Green Roof Conference Yet!

In spite of record rain downpours for five days and five nights, the 4th Annual Greening Rooftops for Sustainable Communities Conference, Awards and Tradeshow, held in Boston in May and co-hosted by the City of Boston and Green Roofs for Healthy Cities, was the most successful green roof conference to date! More than 850 people participated in the conference sessions, tradeshow exhibition, training courses and tours. This constituted a growth rate of 25% over last year’s event in Washington, D.C.! Clearly, the green roof movement is continuing to expand at an impressive rate. As summed up by Dick Gillenwater, Carlisle SynTec, Inc., “The 4th annual conference built on the growing success of the past conferences. It offers a venue that is focused solely on this unique roofing concept of living roofs with their many environmental benefits. Those who attended the conference are there to learn and understand the concept, how it is constructed, and how to maintain the system for the long haul. Carlisle was glad to be apart of this effort to educate the construction community on Roof Gardens.”

More than 850 people participated in the conference sessions, tradeshow exhibition, training courses and tours. This constituted a growth rate of 25% over last year’s event in Washington, D.C.

Boston’s Mayor Thomas Menino opened the conference with a Welcoming Reception for all delegates on the tradeshow floor, and used the opportunity to announce that members of his administration staff had been directed to review new and existing municipal buildings for the incorporation of green roofs and also had requested that City agencies develop an environmental monitoring system to document the benefits of green roofs on storm water, air quality and urban heat island effects. “Here in Boston, we are conscious that the decisions we make today have lasting effects tomorrow,” Mayor Menino said. “And we are implementing plans that reflect our respect for the environment and our desire to become a leader in green building.”

During the course of two busy days, participants had the opportunity to listen to more than 50 speakers addressing such topics as living walls and vertical gardens; selecting plants for peak performance and functionality; and the optimization of energy performance. One of the speaker highlights included the dinner presentation by keynote speaker Dr. John Todd. Dr. Todd addressed more than 120 delegates describing his living machines, or ecological engines, for the treatment of wastes, and the production of foods. Highlighting the works of his mentor, Dr. Malcolm Wells, Dr. Todd inspired those who attended to individually work to make a difference in our environment.

Specified tradeshow hours with no competing sessions ensured that everyone could network on the tradeshow floor and see many of the products and services newly launched at the conference without missing any speakers.

The tradeshow exhibition hours were altered this year to allow delegates and exhibitors the opportunity to enjoy all conference sessions. Specified tradeshow hours with no competing sessions ensured that everyone could network on the tradeshow floor and see many of the products and services newly launched at the conference without missing any speakers. One of the conference exhibitors, Doug Burry from rooflite™ commented on the tradeshow: “As exhibitors, we were very pleased with the growth of the show in both size and quality. It seems as if the show, from an exhibitor’s perspective, has gone from vendors educating and answering basic questions on green roofs, to now actually selling product. It is exciting to see the growth of the industry. The uninterrupted hours on the show floor were a welcome change.” The tradeshow provided a fair balance of national manufacturers and suppliers as well as local consulting and horticultural firms, and next year’s tradeshow will be structured in a similar manner.

Traffic flows through the Tradeshow floor.

A highlight of the conference was our Green Roof Awards of Excellence Luncheon. Established in 2003 to recognize green roof projects that exhibit extraordinary leadership in integrated design and implementation, the projects honoured this year exemplified this mission. Seven awards were presented to residential, institutional and commercial projects for both intensive and extensive gardens. The Green Roof Awards of Excellence winners for intensive and extensive gardens this year included Eastern Village, Silver Spring, Maryland; Ballard Library, Seattle, Washington; Phillips Eco-Enterprise Center, Minneapolis, Minnesota; Seapointe Village Deck Restoration, Wildwood Crest, New Jersey; Mashantucket Pequot Museum and Research Center, Mashantucket, Connecticut; 601 Congress Street, Seaport District, Boston, Massachusetts and 10th @ Hoyt Apartments, Portland, Oregon.

Dr. Beattie is recognized as an industry leader

David Beattie, Penn State University, receiving his Excellence in Research Award from Nancy Somerville, Chair of the 2006 Awards of Excellence Judges Committee and Steven Peck, President, Green Roofs for Healthy Cities.

A new award recognizing Excellence in Research was established this year to honour pioneers in the green roof industry. The first Research Award of Excellence was presented to David Beattie, Pennsylvania State University. David is the Founder and Director of the Penn State Center for Green Roof Research. Established in 2000, the Center’s mission is to promote green roof research, education and technology transfer in the northeastern United States. Well known to everyone at the conference, Dave received a standing ovation when presented with the Award.

Our one soggy note was the weather’s impact on the pre-scheduled local green roof tours. However, many delegates braved the elements and had a chance to see some spectacular projects including Harvard Square; Boston Common and Public Gardens; and Kendall Square and MIT.

Bookending the conference were several new courses that are now part of our burgeoning accreditation program -- four new training courses were presented, several of which were sold-out. The ever-popular Design 101 – Introduction to Green Roof Design was filled for both sessions, and the advanced Design and Implementation 201 had its inaugural debut to an enthusiastic response. Half day sessions were presented on Biodiversity, ASTM and FLL Standards and Policy Development. Positive delegate reaction to these new workshops will ensure the return of the workshops at our next conference.

Committee Chairs hosted meetings for members on Corporate Membership; Research and Policy. All corporate and individual members were invited to participate and discuss potential research projects, policy development in municipalities throughout North America and overall industry development. Many members networked these meetings and have provided to us at GRHC new ideas to explore on behalf of the membership and industry. Peter D’Antonio, Sarnafil Roofing, and member of the Corporate Members Committee, emphasized the importance of these networking opportunities: “The technology sharing at this event is vitally important to develop in North America in this evolving field. All involved in green design, LEED, municipal policy and planning, and concerns with heat island mitigation issues should attend. An excellent program and networking opportunity!”

The culmination of this event was the result of hours of work and support from so many individuals on different committees volunteering their time and expertise for the past year. While too many to name individually, I would like to recognize the committees: Boston Local Host Committee (Co-Chaired by Peter Lowitt, Devens Enterprise Commission and Bryan Glascock, City of Boston, Department of the Environment); 2006 Awards of Excellence Judges; Speaker Selection Committee; GRHC Policy Committee; GRHC Research Committee; GRHC Corporate Members Committee; GRHC Training Committee; and GRHC Training Peer Reviewers. Thank you – your commitment is recognized and appreciated.

Of course, our corporate sponsors were critical in ensuring the successful presentation of the conference, and recognition must also be given to The City of Boston; American Society of Landscape Architects; Camp, Dresser and McKee (CDM); Skanksa; American Hydrotech; Colbond; Eco-Structure; Environment Canada; Environmental Design and Construction; McGuire Woods; Garick/Rooflit; Sarnafil; Soprema and the US General Services Administration (GSA). Our partnerships with more than 30 varied associations – national, regional and local – ensured that we got the word out to you and their on-going support of our programs is most appreciated.

Plans are already underway for the 2007 5th Annual Greening Rooftops for Sustainable Communities Conference, Awards and Tradeshow in Minneapolis. Enthusiasm is high and numerous local committee members have begun the plans of making next year’s event our biggest yet! I hope to see you in Minneapolis in May.

Jennifer Sprout is Director, Conferences and Special Events, Green Roofs for Healthy Cities and may be reached at: jsprout@greenroofs.org.

Compost Utilization Goes Through the Roof
Center for Green Roof Research at Penn State University uses compost in its media studies and plans to explore microbial communities.

Originally published in the March 2006 issue of BioCycle magazine, the Journal of Composting & Organics Recycling. Reprinted with Permission.

Penn State Center for Green Roof Research. Photo Courtesy Dr. Robert Berghage.

The Center for Green Roof Research at Penn State University uses compost in its media studies and plans to explore microbial communities.

At the Penn State Center for Green Roof Research in University Park, Pennsylvania, horticulturalists, plant physiologists and agricultural engineers are collaborating to study the many aspects of green roofs and their effects on the environment. From looking at broad questions of how green roofs mitigate storm water runoff to specifics in terms of modeling the evapotranspiration rates in these systems, the Center is dedicated to providing scientific answers for this fast growing sector of green technology. Fortunately for compost producers, the use of organic materials in this technology is proving essential.

A green roof can be either intensive or extensive based on the degree of maintenance required to grow plants in specially formulated green roof manufactured soils or “media” as it is often referred to in the industry. Intensive green roofs require a high degree of maintenance and can be thought of as “roof gardens.” Media depths range from approximately 18 to 213 cm (7-84 inches) depending on the plant species used. Typically media depth must be greater than 25 cm (approximately 10 inches) to support an array of plant life in these systems. The additional roof load capacity needed to support such media depths is between 300 - 1,500 kg/m2 (approximately 60-300 lbs/ft2 or psf; pounds per square foot) depending on a number of factors such as the slope of the roof, type of manufactured soil used, whether or not irrigation systems are installed, and human traffic calculations. For comparison, typical single family homes in mild climate regions of the U.S. have additional roof load capacities between 10 and 30 psf. An intensive green roof system would not be appropriate for these types of roof structures without significant structural adjustments.

In contrast, an extensive green roof system typically requires a media depth of only 5 to 20 cm (approximately 2-8 inches) and is more functional in nature compared to an intensive green roof system; functional in the sense that its primary focus is for implementation as a Best Management Practice or BMP for storm water management. Additional roof load capacity needed for an extensive green roof system varies between 90 and 250 kg/m2 (approximately 16-50 psf) depending on the same factors as outlined above for intensive systems). The studies carried out at Penn State all involve extensive green roof systems. It should be noted that load capacity ranges are generalized. Each green roof installation is unique and structural engineers should be consulted for the final load and design requirements.

History of the Center
The Center for Green Roof Research at Penn State began as an idea formed during a European trip that the Center's former director, Dr. David Beattie, an associate professor of Horticulture, took in the late 1990s. At the time, green roofs were not well known in North America despite over a century of usage in several European countries, mainly Germany. A car bumper manufacturer based in Malvern, Pennsylvania provided a much needed catalyst. JSP International Inc. approached Beattie and his colleague, current Center Director Dr. Robert Berghage, also an associate professor in horticulture, about additional markets for their porous expanded polypropylene or PEPP compressed plastic mats.

One possible application was as a layer in a built up green roof. Beattie and Berghage looked at two different species of plants, a sedum and a grass, planted in various mixtures of manufactured soils using the PEPP. Comparing temperatures on a conventional plastic sheeted roof, a gravel covered roof, and a green roof, they discovered just how well the green roof system did in terms of mitigating heat effects. During the summer of 2000 with an ambient temperature of 88°F, the temperature in the green roof media was 82°F. The plastic sheeting and gravel roof measured 140 and 118°F, respectively. In terms of the plant species used in the green roof system, sedum performed better than grass in terms of its ability to weather temperature and moisture extremes. Sedum, a relative of the cactus, grows low to the ground and doesn't shed much dead plant material. It also requires very little in the way of maintenance and nutrient requirements.

Because of the success of the initial partnership with JSP International Inc., the Center was able to obtain funding from other sources such as American Hydrotech and Carlisle SynTec, two green roof industry giants, and state and federal sources like the Pennsylvania Department of Environmental Protection (DEP) and the U.S. Environmental Protection Agency (EPA), respectively. The Center officially began in 2001 with a research site at the Russell E. Larson Agricultural Research Center in Rock Springs, PA, and a mission to demonstrate and promote green roof research, education, and technology transfer in the Northeastern U.S. The Center has become a leader in studying various media suitable for growing extensive green roof plants as well as providing quantifiable data necessary to answer critical questions about the effectiveness of green roofs in mitigating runoff from storm water events.

Recent Research Projects
One of the first studies carried out at the Center, and part of a master's thesis project by Julia (DeNardo) Hunt, a former graduate student in Agricultural and Biological Engineering (ABE), was an investigation into the mitigation effects green roofs have on storm water runoff. Dr. Albert Jarrett, a professor of Agricultural Engineering, was DeNardo's major advisor and supervised the study along with Beattie and Berghage. The research quantified the importance of green roofs in attenuating or reducing runoff. According to Jarrett, “The benefits of green roofs in attenuating storm water runoff are clearest if one looks at four things: 1) runoff volume reduction, 2) peak runoff rate reduction, 3) overall runoff delay, and 4) peak runoff delay in these systems.” To look at these four variables, six buildings (4.65 m2; 48 ft2) were constructed; three with extensive green roof systems and three with conventional, standard asphalt roofs both with roof slopes of 1:12 (Figure 1).

Figure 1. Building layout and schematic cross section of DeNardo study at Center for Green Roof Research (DeNardo, 2003).

Each extensive green roof system consisted of a waterproof membrane and root barrier, a drainage layer, growth media, and vegetation (Figure 2). The growth media had a depth of 7.8 cm (approximately 3 in.) and consisted of 12.5 percent sphagnum peat moss, 12.5 percent coir (coconut fiber), 15 percent perlite, and 60 percent hydrolite for a 75 percent mineral or inorganic material to 25 percent organic material ratio (v/v). Above the growth media was a 2.5 cm (1 in.) thick layer of PEPP into which vegetation (Sedum spurium) was transplanted.

Figure 2. General profile of an extensive green roof system (DeNardo, 2003).

The buildings at the Center for Green Roof Research have their own storm water collection systems installed complete with gutters, downspouts, and collection barrels. The first event occurred on October 25, 2002, producing a cumulative rainfall total of 2.39 cm (.94 in). Green roof runoff total measured 1.93 cm (.76 in) for a runoff volume reduction of 0.46 cm (0.18 in) or 19 percent. The maximum rainfall intensity was measured at 6.6 mm/hr (0.26 in/hr) while the maximum runoff rate from the green roof was 4.1 mm/hr (0.16 in/hr) for an intensity reduction of 38 percent. In terms of delays, runoff from the green roof took 4 hours to begin and 1 hour from the time peak rainfall intensity was recorded to the time peak runoff occurred. Evidence such as this gives storm water engineers valuable information in planning storm water infrastructure for urban and suburban areas. Extra time to absolve rainfall events in these areas is critical to managing water quality and adds to the attractiveness of using green roof technology as a Best Management Practice or BMP in construction.

Capture systems include gutters, downspouts and collection barrels.

Other key findings from DeNardo's study were: 1) green roofs retained on average 6.5 mm (.26 in.) or approximately 45 percent of total rainfall during the period of study (two months), 2) peak runoff rates averaged 2.4 mm/hr (.09 in/hr) or 56 percent of the peak rainfall intensity, and 3) runoff from green roofs was delayed an average of 5.7 hours.

Jarrett has since expanded on DeNardo's work developing models for the way green roofs respond in two typical storm water scenarios: extreme storm events and cumulative annual rainfall. “Understanding how green roofs can help us manage storm water begins by looking closely at these additional elements,” Jarrett comments. Two-year (2.6 in/day) and 100-year (5.3 in/day) extreme rain events were simulated. In addition, Jarrett used weather data from State College, PA for a 27 year period (1976 to 2003) to simulate how well a green roof would reduce the cumulative annual rainfall (mean annual rainfall = 40.3 inches). Results of Jarrett's modeling work showed that with a 2 year storm event in July with 5 dry days prior to the storm, green roofs could reduce the peak intensity of the runoff by 85 percent (compared to no green roof) and the volume of runoff by 61 percent. The 100 year rain event also in July and also with 5 dry days prior could reduce peak intensity of runoff by 60 percent and volume by 30 percent. Numbers such as these are the lifeblood of making technologies such as green roofs an attractive alternative to conventional storm water management strategies.

Other studies have followed and helped answer other critical research questions. Berghage and Beattie were interested in media depths and how different green roof plants might respond in these systems with varying drought situations. Christine Thuring, a former graduate student in the Department of Horticulture, with both Beattie and Berghage acting as her coadvisors, used this interest as part of her master's thesis project to investigate a suite of popular green roof plants grown in different types of media at varying depths and in different drought regimes. As mentioned above, plants in an extensive green roof system can be exposed to extreme temperatures and moisture levels. As extensive green roof systems are less deep than intensive systems, there is a tradeoff between using deeper media to conserve plant available water during these extremes and adding weight to the roof structure and hence cost to the project. Thuring's project looked at how five different plant species (Sedum album, S. sexangulare, Delosperma nubigenum, Dianthus deltoides, and Petrorhagia saxifraga) responded (when grown) in three different depths (3, 6, and 12 cm) of two different media (expanded shale and clay) in two different types of drought situations responded.

Switch to Compost
The growth media for Thuring's study consisted of either 85 percent (by volume) expanded clay or shale as the mineral component and 15 percent (by volume) pelletized spent mushroom compost from Laurel Valley Soils in Avondale, PA as the organic component. The switch to composted organic material from sphagnum peat moss and coir fiber in the previous study was made to make use of a recycled waste product, spent mushroom compost, and promote sustainability issues in the region. Thuring adds that “compost usage in green roof media from a sustainability perspective makes a lot of sense and should be integrally tied to the makeup of green roof media mixes. Specifically, research in the area of water retention and the decomposition process by different composts as potential components of green roof media would be extremely beneficial.” Echoing Thuring's comments, Charles Friedrich, a licensed landscape architect for Carolina Stalite Company, in a paper presented at the Greening Rooftops for Sustainable Communities in Washington, D.C. last year, stated that compost “is a preferred source for the organic component in green roof system media because of its high nutrient and microbial count, and it is politically correct because of its recycling value.” However, he adds, “Care must be taken when selecting the source of compost; proper stability/maturity, particle size, and feedstock source of the product should be considered.”

The two inorganic substrates in Thuring's study were used because of their popularity in North American green roofs and do not reflect the Center's promotion of one over the other. Thuring notes that “locally available inorganic materials from regional tile or brick manufacturers can minimize transportation costs and provide ecologically sound choices in terms of green roof media.” All experiments were carried out in a 4 x 30 m polyethylene greenhouse tunnel with all media placed in propagation flats modified to achieve the desired depth requirements. Air circulation, temperature, and irrigation were monitored and regulated throughout the study.

Key findings from Thuring's study were: 1) media depth most affected the growth of all plants, 2) herbaceous species did not survive in 3 cm (1.2 in) depths of either media, nor in 6cm expanded shale when subjected to drought conditions, 3) plant growth under drought was better in the clay compared to the shale, and 4), irrigation in the first weeks after planting is beneficial for plant establishment and performance. Indeed, initial irrigation proved vital for the herbaceous taxa and valuable for long-term performance by the succulents (not including S. album). In terms of design implications, Thuring's study showed that media depth and type, as well as water availability, are important considerations when selecting species for extensive green roofs. Succulent species performed well in 6 cm (2.4 in.) media, but always did better in clay versus shale. As for herbaceous species, green roof media depth should exceed 6 cm (2.4 in.), however more research on the use of such plants, especially native species, is needed.

Current and Future Studies at the Center
Dr. Shazia Husain, a plant physiologist and visiting doctoral scholar, has begun experiments that expand upon the knowledge gained by previous research described above. Specifically, Husain has three areas of focus; elucidating mechanisms of evapotranspiration in green roof plants, determining plant responses to various mixtures and particle sizes of inorganic substrates and compost, and investigating potential ozone effects on green roof plants. Using lysimeters with temperature and moisture sensors attached, Husain is working to quantify evapotranspiration rates in Crassulacean Acid Metabolism plants or CAM for short. Husain states, “These plants, mostly succulents, have stomates that open and close during different times of the day to maximize water retention and minimize water loss. Knowing the mechanisms that are involved with these CAM plants can help scientists understand more about which plants are best suited for green roof systems and how they function to attenuate storm water runoff.” In addition to studying the CAM mechanisms in these systems, acid buffering capacity, pH, electrical conductance, and nitrate levels are being monitored.

As there are numerous inorganic substances marketed for use in green roof media with equally numerous claims for their respective products' superiority, Husain is performing work on various expanded shales and clays of differing particle sizes. Additionally, Husain states, “Mixing these inorganics with organics such as compost is critical to rapid establishment of green roof vegetation. Approximately 20 percent organic material and 80 percent inorganic appears to be the best mix in terms of plant growth response to date,” Husain continues, but she cautions against hard and fast volumetric percentage recommendations. “Each system is unique and the goal of each green roof system must be considered.”

Husain is also working on the effects of ozone on green roof plants. While largely an unknown area of research in terms of green roofs, Husain hopes to build upon what is known about ozone formation and apply it to this “green” technology. According to the U.S. Environmental Protection Agency (EPA), ozone occurs in urban areas where expansive concrete, lack of vegetation, and fossil fuel burning are prevalent contributing to a ground level formation of ozone and localized temperature increases known as “heat islands." Heat islands can affect vegetation growing in urban areas interfering with plants' abilities to grow and store food. The use of green roof technology has been suggested as a way to mitigate the effects of heat islands in metropolitan cities, but the mechanisms involved in how green roofs do this are still not completely understood.

Ozone (O3) is a colorless gas with a pungent odor. It's found in two layers of the atmosphere, the stratosphere and the troposphere. In the stratosphere, ozone provides a protective layer shielding the Earth from ultraviolet radiation's potentially harmful health effects. At ground level (the troposphere), ozone is a pollutant and contributes to the formation of smog (from www.epa.gov). Husain has proposed a number of experiments to look at the extreme effects of ozone on green roof plants to better understand how atmospheric conditions can be benefited by as well as cause harm to green roof systems.

In terms of future studies at the Center, a recent PhD candidate in Horticulture with experience performing bioremediation projects around the world has expressed interest in investigating the microbial community assemblages in green roof media. Nutrient cycling issues as well as the implications for green roofs to act as potential pollution treatment systems are anticipated as areas of exploration.

Recent Developments
The Center just received additional funding from American Hydrotech in September of 2005. This funding has enabled the Center to effectively double its data gathering capacity at the Rock Springs research site. Known as the HB (Hydrotech Building), its roof now boasts two 1:12 slopes, one facing north and the other south, with an effective roof area of 27.9 m2 (288 ft2), equal to all of the original six buildings' roof areas combined.

In the final analysis according to Berghage, “Green roofs are an excellent technology for use in rural, suburban, and urban areas where attenuating storm water runoff is critical. Green roofs are aesthetically pleasing, and there is strong evidence that they effectively mitigate storm water runoff and heat island effects in large metropolitan areas.” But, Berghage adds, “in the U.S., regulatory agencies are sometimes slow to adapting new technologies and 'hard numbers' are necessary to make these same regulatory agencies take notice. Quantity right now in terms of how much green roofs can store and delay storm water and storm water runoff, respectively, is the driver for research in this area for the foreseeable future.”

The Center for Green Roof Research has come far in its short five year history. From an idea that started across the Atlantic to the reality of a research center located in central Pennsylvania, scientific curiosity is a powerful force. Thankfully, with scientists like Beattie and Berghage, who carried out the first experiments at the Center before it was officially called a “Center,” their collective curiosity appears to have been in large supply. And with engineering expertise from Jarrett, “hard numbers” were generated early to provide the quantification necessary to show green roofs could adequately mitigate storm water runoff. Graduate students have also proven to be an essential part of the Center's success with DeNardo, Thuring, and Rezaei answering essential and fundamental questions about this relatively new green technology in their theses. Husain's role as a plant physiologist at the Center will undoubtedly shed more light on the mechanisms of how plants in these systems work to slow storm water runoff as well as other benefits. The Center appears to be on a mission with a team of scientists dedicated to generating results that are going through the roof.

Drew Mather is currently working for the USDA's Natural Resources Conservation Service as a Soil Scientist in Southwestern Wyoming. Drew graduated from Penn State in 2005 with a Master of Science in Soil Science; his research dealt with organic matter decomposition in composting and vermicomposting systems.

Contact Drew Mather via e-mail at: drew.mather@gmail.com.

Publisher's Note: Learn more about the Penn State Center for Green Roof Research in the Greenroof Projects Database, and visit their website here. Read about Christine Thuring, our Student Editor, and her studies at Penn State here.

2003

december 2003 - The London Biodiversity Partnership, Wild Roofs: Current research into green roofs and biodiversity in London - By Dusty Gedge

november 2003 - Ecoroofs Everywhere, Community Based Ecoroof Projects & Public Education - By Anthony Roy

october 2003 - The Earth Pledge Foundation, Greening Gotham: The Earth Pledge Green Roofs Initiative - By Colin Cheney & Marisa Arpels

august 2003 - D.C. Greenworks, Community, Environmental Sustainability and Green Roof Technology - By Dawn Gifford

june 2003 - Northwest EcoBuilding Guild, Promoting Residential Greenroofs in Seattle and the Pacific Northwest - By Patrick Carey