Interview with Green Roof for Healthy Cities Founder Steven Peck

20 05 2011

Pinnacle at Symphony Place Green Roof , Nashville, TN

The following is a brief email interview we conducted with Steven Peck, founder and president of Green Roofs for Healthy Cities, a non-profit industry association promoting the planning, designing and building of green roof, and green walls.

GrID: It was good news to hear the green roof market continued to expand in 2010. We hope the trend continues. You were recently quoted in The Dirt, stating this expansion constituted an addition of 8-9 million square feet of green roofs. Can you provide more detail into what characterized this expansion (i.e. type of green roofs, clients, project types, etc)?

Steven Peck: We just posted a report on the industry survey at that contains more detailed information about what types of buildings are green roofs being implemented on, the types of green roofs being installed, locations etc.   It is a free, downloadable report that contains all of this information.

GrID: You acknowledge a lot of this growth is taking place in cities that are encouraging the development of green roofs through  “significant public policy support”. What best policy or program practices are you seeing used most effectively in the United States? Any others you would like to see instituted?

Steven Peck: Most of the policy tools being used in the United States are economic in nature, in the form of tax incentives, increases in floor area for new developments, and grants averaging $5 per square foot.  There are also procurement requirements for government buildings – a good place to start – as well as for any building that is receiving some for of government financial assistance.  For publicly owned buildings, the fact that green roofs, if properly design, installed and maintained by a Green Roof Professional (GRP)  extend the life expectancy of the waterproofing by two times or more, is a significant economic benefit for tax payers.  Billions of square feet of flat roofs are torn off and replaced each year at enormous public and private cost.   

The new versus retrofit markets are different, and the nature of the incentives to encourage green roofs varies from building type to building type, because the economics are very different.  This makes it difficult to generalize about effectiveness.  In buildings where green roofs can provide more direct benefits to the building owner – like condomiums, buildings that are air conditioned, schools and hospitals, the economic case is stronger.  In buildings that are very cheaply constructed, not air conditioned, and the roofs are innaccessable to the occupants or public, greater government incentives are likely to be required owing to the fact that the benefits are more in the public realm.  For example, green roofs are widely regarded as a best management practice by governments in dealing with the need to reduce and slow down stormwater, which in many cities results in significant water quality problems.  So building owners can meet regulatory requirements by installing green roof systems.  

In Canada, two jurisdictions, the City of Toronto and the City of Coquitlam have made green roofs a requirement in various classes of new development.  The Green Roof By-Law in Toronto requires that all buildings over 2,000 square meters of floor area (with the exception of new industrial buildings) must install a green roof.  This policy has already resulted in an estimated 1 million square feet of new green roofing that is now in the planning phase.  It also levels the playing field and provides the design community with the opportunity to skip the ‘justification’ of the green roof and move right to ‘how do we get the most benefit’ from the green roof stage. 

GrID: The new ANSI Fire and Wind standards seem to potentially have a big impact on the aesthetics of green roof design. Can you give us some insight into why and how they were developed? What has been the reaction to the new standards from the design side of the industry? Are they being widely used?

Steven Peck: The standards were developed because of largely unfounded concerns about these issues, but we need to address them in order to remove a potential regulatory barrier.   During the development of the standards, we tried to maintain as much flexibility as possible in terms of design.  It remains to be seen how widely these standards will be adopted, and ultimately what effect they will have on the aesthetics.

GrID: Green roofs can be initially significantly more expensive than traditional commercial roofing. As the green roof market has matured, are you seeing pricing coming down and/or seeing creative financing mechanisms that make it easier for property owners to choose to build a green roof on a new or existing building?

Steven Peck: Generally speaking, as a market begins to mature prices drop as a result of competitive pressures, more efficient implementation, and innovation in product and service delivery.   This has happened in mature markets like Germany, and it is happening in more mature markets in North America.  There is a danger however – buyer beware – that in just using price as a determinant, you may end up with a green roof system that fails to work effectively.  These are engineered systems and all of the parts have to work together to achieve water tightness, structural integrity and the long term health of the plants.   We’ve spent 10 years developing professional training programs in order to establish and promote best practices in the industry.  This has culminated in the development of an occupational standard for a Green Roof Professional.   There are more than 450 GRPs in the marketplace, so make sure that you are working with a GRP to help to ensure that your green roof doesn’t disappoint you.   

GrID: What trends are you seeing in the green roof industry? What will the future of green roofs look like?

Steven Peck: We have recently developed three new courses that reflect some of the trends in the industry.  Advanced Maintenance we launched in April in Washington to provide more detailed information on how to design, budge and implement effective maintenance practices.  Maintenance neglect is one of the main causes of problems on a green roof.   In November of last year, we launched a half day course on Urban Rooftop Food Production, a hot topic these days.  We’ll be providing training in Toronto and New York this summer, two jurisdictions where there is a strong urban food movement.   Water.  In many regions, water shortage is already a problem, and only likely to get worse.  Last year we developed an introductory course on Integrated Building and Site Water Management, in partnership with the American Society of Irrigation Consultants.   This half day course will be available online, in our Living Architecture Academy, in June.   Increasingly, green roofs will be integrated with other forms of green infrastructure, like green walls, and be designed to perform multiple functions – cool cities, biodiversity, food, improve photo-voltaic efficiency.   We’ve still only scratch the surface of the full potential of these technologies. 

Water and the Southeast False Creek Olympic Village

22 02 2010

Cover of Water + Building Landscape (Chapter 6)
from The Challenge Series Website

Staying with the Olympic theme from last week’s post on the Vancouver Convention Centre, the Southeast False Creek Olympic Village is another spectacular example of sustainable building in Vancouver. The Olympic Village will house the athletes throughout the games. Afterward, it will become the home of over 16,000 residents. The following is a link to the diversity of uses that will be or are already included in the development.

A website called “The Challenge Series” has been set up to help educate the public about the Olympic Village’s sustainable features. A well-designed booklet describing the sustainable features of the development is available on the site in pdf format. One that particularly caught my attention was the Water + Building Landscape section (See Cover Above). It explains many sustainable water strategies employed throughout. Some highlights include:

  • The design team recognized the size was not large enough to handle all of the stormwater in the constructed wetland incorporated into Hinge Park. As a result, the team prioritized the water into a two-tier system. The first tier was considered the “cleaner” water that came from the rooftops and podium sections of the building. This water was directed to the cisterns in the basements of each building. The water was then used to flush toilets, supply water features, or irrigate the landscape. Additional water overflowed the cisterns and entered the South False Creek. The second tier included “dirtier” water. This water came from the roadways and other areas. The water from these areas was directed into the constructed wetland or underground gravel/sand infiltration cells.
  • The development reduced potable water use by 40 percent.
  • The site plan incorporates a number of water features that utilize the water collected on the site. The circulation through the water features provides a means of making what would otherwise be invisible visible, while at the same time improving the quality of the water.
  • 287,000 s.f. of green roof covers the development. The roofs include both extensive and intensive green roofs. This was in part because the City of Vancouver mandated that 50% of the roofs be green roofs.
  • The City also mandated the inclusion of urban agriculture at a rate of 24sf for 30% of the units whose balconies were less than 100sf.

The development has received LEED-ND Platinum certification. I look forward to seeing it one day when I return to Vancouver. There have been a number of articles on the development, but I highly recommend reading the information found on The Challenge Series website.

-Brian Phelps

Interview with Portland BES Part 1 of 3

3 02 2010

Portland Building (Location of Portland BES Offices)
Source: City of Portland, Environmental Services ©2009

The following is the first part of an email interview I recently conducted with Emily Hauth, project manager with Portland Bureau of Environmental Services (BES)’s Sustainable Stormwater Management Division. Their agency has been a leader in sustainable stormwater implmentation over the last twenty years.

Green Infrastructure Digest (GrID): The City of Portland has been and continues to be a leader in implementing green infrastructure facilities. Please tell our readers a little bit about the work the Bureau of Environmental Services (BES) is doing in regard to increasing the use of green infrastructure. What new innovations should we expect to see out of BES in the coming years?

Ms. Emily Hauth: Our sustainable stormwater management solutions have evolved from a single purpose regulatory driven approach to one that achieves multiple objectives. We are designing our urban landscapes and street systems with an eye toward community enhancement, cooling of the air and water, increased wildlife habitat and greenspace, safe bike and pedestrian linkages, greenway connections to services and amenities, and of course capturing and treating stormwater at the source on the surface. In this way we are achieving watershed health goals and meeting regulatory compliance while informing a new approach to urban development.

We are incorporating green infrastructure approaches into our policy development and planning processes. We have a number of policy initiatives that recognize green infrastructure solutions as a smart way to plan for watershed health and the city’s future and direct city bureaus and agencies to cooperatively plan and implement green infrastructure elements as part of all work programs. Our bureau works collaboratively with other City bureaus and agencies such as our Bureau Of Transportation and the Portland Development Commission on projects that promote environmental concepts while addressing auto, pedestrian, and bicycle safety. We are also fully integrating our watershed health and stormwater/sanitary collection goals into our Systems planning process. Portland’s Grey to Green initiative, established in 2007, sets a 5-year goal to increase green infrastructure elements throughout Portland including 900 Green Streets, 43 acres of Ecoroofs, and over 50,000 new trees.

In one particular area of the city where pipes are failing or undersized, we are incorporating green street facilities into the solutions plan. This area is referred to as Tabor to the River. In this area alone, we will be constructing 500 green streets. We’re also working closely with targeted private property owners to help them manage stormwater on their sites and play a role in the solution. All future work to address similar issues will follow this model of combining grey and green infrastructure solutions.

We don’t feel we have all the answers so we continue to ask ourselves, is it working? We continue to monitor our facilities, modify designs, research components such as plants and soils, to refine our knowledge base and maximize facility function and performance. We’re always looking for efficiencies in design and construction so we’re evaluating use of modular or prefabricated components for sustainable stormwater solutions. Other innovations we’re exploring include using a curbless green street design, new design options that manage both public and private runoff, and green walls that manage stormwater. We’re also developing a volunteer green street maintenance program that engages the community while helping the city meet its maintenance needs.

Planter at Mississippi Commons
Source: City of Portland, Environmental Services ©2009

Part 2-On Friday

-Brian Phelps

Finding Water in the Desert

22 01 2010

There have been a few articles lately about the new Underwood Family Sonoran Landscape Laboratory which is a part of the School of Landscape Architecture at University of Arizona. Arizona is known for its arid climate, but this project uses an innovative take on irrigation to provide a lush landscape for this jewel of a space.

Photo Courtesy of Ten Eyck Landscape Architects Inc
Photo by: Bill Timmerman

In addition to creating a wetlands biome, complete with an 18,000 gallon pond, the project provides an 11,600 gallon cistern for water harvesting. The water harvesting is provided from four sources – and rainwater is not the largest source of water. Of the approximately 250,000 gallons of water harvested each year about 40% comes from condensate from the air conditioning units, 33% comes from rainwater runoff from the roof, 18% from well water blow off and 9% from greywater collection (from sinks and drinking fountains. This water harvesting accounts for 83% of the water required for the landscape on an annual basis.

Photo Courtesy of Ten Eyck Landscape Architects Inc
Photo by: Bill Timmerman

In addition to the water harvesting, the garden includes a significant green wall with planted vines adding to the shading from the hot desert sun on the southern façade of the building.

Next up, they are looking at creating a desert green roof which can be monitored for research data.

If this is available in a desert environment, think of the potentials for harvested water elsewhere.

University of Arizona News had an article about the facility that provides more information on the project. Check out their photo of the large water collection system in action. Ten Eyck Landscape Architects were the landscape architects for the project.

Photo Courtesy of Ten Eyck Landscape Architects Inc
Photo by: Bill Timmerman

Photo Courtesy of Ten Eyck Landscape Architects Inc
Photo by: Bill Timmerman

-Kim Hawkin

A Vision: Green Roofs in Birmingham

20 01 2010

Downtown Birmingham, AL with Green Roofs
Rendering by: Hawkins Partners, Aerial from Live Local Maps (Now Bing)

A few years ago, I put this illustration together for a green roof presentation to the Birmingham branch of the Alabama Chapter of the USGBC. Images like this provide a compelling illustration of what the city could look like if every building added a green roof.

-Brian Phelps

Cooling Our Cities: An Interview with Dr. David Sailor

23 12 2009

I had the pleasure of conducting an email interview with Dr. David Sailor, the director of the Green Building Research Laboratory (GBRL) at Portland State University (link to resume). He is a leading researcher in the effects of green roofs and energy use in buildings and the impact green infrastructure can have on cooling our cities. He and his colleagues have developed tools to help quantify these impacts.

Green Infrastructure Digest (GrID): I understand that this year you became the first Director of the Green Building Research Laboratory (GBRL) at Portland State University. What is the focus of the research you are conducting at GBRL? Why and how was GBRL started?

Dr. David Sailor: The Green Building Research Laboratory was essentially an outgrowth of the funded research agendas of myself and my GBRL colleagues. This group of Portland State University faculty included Graig Spolek in Mechanical and Materials Engineering, Loren Lutzenhiser r in Urban Studies, and Sergio Palleroni in Architecture. Over the years we had developed a number of collaborative projects and decided it was time to build upon this collaboration by creating a physical laboratory where we, our students, and our industry partners could work together on fundamental and applied research to benefit the green building industry.

We pitched the idea of a collaborative shared-user facility to Oregon BEST and to the PSU Center for Sustainable Processes and Practices, both of whom agreed to provide the initial funding for the lab. As a result, while the lab was initiated by four faculty members at Portland State, it really serves as an Oregon University System shared resource.

There really is a wide range of research activities going on in the lab. This includes several monitoring projects with local builders, property owners, and school districts with a focus on understanding the thermal and moisture performance of building envelopes as well as the indoor environmental quality of these buildings. We also continue to make advances in the monitoring and modeling of green roof performance. Personally I have been involved in a number of monitoring projects and in creating an energy modeling tool for evaluating the energy performance of green roof design decisions. My colleague Graig Spolek has been using some of the GBRL water quality testing equipment to better understand the chemical composition of green roof runoff. We are also using GBRL facilities to understand the interactions between buildings and the urban atmospheric environment. This involves both modeling and field measurements.

GrID: A lot of your research has been focused on green roofs and heat island mitigation through the use of green infrastructure. How significant of a role does green infrastructure have in addressing thermal heat gain within our built environment? It appears through the tools you have developed for the MIST program that you have been able to quantify these impacts? Can you explain to our readers, what the MIST program entails?

Dr. Sailor: Yes, my research career actually started with a focus on urban heat island mitigation through use of urban vegetation and highly reflective (high albedo) urban surfaces. The US EPA funded some of my early modeling efforts in an attempt to provide a quantitative assessment of how much potential there is for cities to cool their summertime air temperatures through city-wide modification of urban surface characteristics (vegetation and albedo). We used regional scale atmospheric models of about 20 cities across the US to create information on the potential impacts of such mitigation on summertime urban air temperatures, peak ozone concentrations, and energy consumption. The result of that was a fairly user-friendly urban heat island screening tool – the Mitigation Impact Screening Tool – or MIST. The tool uses fairly simple interpolation and extrapolation of our modeled results so that policy makers in any US city can easily estimate the order of magnitude of the impact that any particular mitigation strategy might have in their city. I like to emphasize the “S” in MIST – this is a Screening tool. Ultimately, any policy decisions that involve significant investment of public funds to mitigate the urban heat island ought to be based on a more thorough, city-specific analysis – which of course can start by running MIST.

Thermal Imaging Photo of Portland Buildings (Summer 2009)
Source: Green Building Research Laboratory (GBRL)

SP1=Typical Washed Rock Roof Membrane Cover (151.5F)
SP2=High Albedo (.75) White Roof (110.0F)
SP3=Low Albedo (.10est.) dark roof, NE Exposure (135.0F)
SP4=Low Albedo (.10est.) dark roof, SW Exposure (144.0F)
SP5=3-month Old Green Roof (Essentially Bare Soil) (100.0F)

GrID: Many of our readers would like to know if green roofs can reduce energy use in buildings and if so, by how much? What factors most influence the outcome? What light has your research been able to shed on this pressing question?

Dr. Sailor: The thermal performance of green roofs depends on a number of factors. Specifically, roof construction, depth and properties of the growing media – including soil moisture, plant characteristics and coverage, and local climate characteristics all affect heat transfer into the building. The role of the roof on building energy consumption also depends on internal building loads and schedules. An often overlooked point is that the performance of any alternative technology depends on the baseline that is used for the comparison. As a result, I hesitate to assign a specific level of savings that could be expected from green roof implementation. That said, the various simulations that we have conducted for cities across the US have shown that a green roof can have comparable summertime air conditioning benefits to those achieved by white or “cool” roofs. In contrast to a cool roof, however, the added thermal insulation of a green roof can result in a wintertime heating energy savings whereas the cool roof generally has a wintertime heating penalty. In general, our model shows that the annual air conditioning energy savings associated with replacing a typical roof with a green roof are on the order of 100 to 500 kWh for each 1,000 sq. ft of green roof. What is important to note, however, is that the energy savings are just one component to be considered in determining the economic and environmental value of green roofs. It is likely that the stormwater, urban heat island, and extended roof life aspects of green roofs are equally important.

GrID: The energy savings for green roofs are more modest than I would have expected. I remember some of your findings displayed at the 2007 Green Roof for Healthy Cities conference in Minneapolis had energy saving ranges between 4-12% depending on the location.

Dr. Sailor: Yes, the air conditioning energy savings by themselves are modest. The numbers I gave above are just for the Air Conditioning savings. Heating savings can be comparable or more important depending upon the location and roof design.

The data that you recall from the Minneapolis meeting were specified in terms of HVAC savings. The numbers from that poster were 3-6% annual cooling electricity savings in Minneapolis, 2-5% for Phoenix, and 3% in Orlando. For heating energy savings we had found up to 10-14% for Orlando and Phoenix, and about 4% for Minneapolis. While the model has changed some, these values are generally consistent with what we are still finding.

The nominal ranges that I described from our current model simulations are for a green roof in comparison to a roof that has an albedo of 30%. Both roofs are assumed to be insulated to modern energy code standards. The actual savings depend very much on the baseline used for comparison with the current tool providing a conservative estimate that might significantly underestimate savings for some applications. Also, it should be noted, that depending upon soil depth, vegetative lushness, local climate, and building type, a green roof can actually INCREASE the energy cost for heating or cooling in a building. The tool can provide the necessary feedback to avoid such a situation, and then help you move toward an optimum design with respect to total energy performance.

GrID: Oftentimes, engineers modeling the energy use of a building find it difficult to accurately simulate the effects of green roofs on energy use. Can you tell our readers about the plug-in your have created for the Department of Energy’s (DOE) EnergyPlus modeling software? How has this enabled mechanical engineers to more accurately model the effects of green roofs? How widely used is it?

Dr. Sailor: We developed a physically-based model of the energy balance of a vegetated roof and integrated this model into EnergyPlus. This module is now a part of the standard release of EnergyPlus and allows the energy modeler to explore how variations in green roof design can impact whole building energy performance. It is hard for me to assess how widely used it is among practitioners in the field, but I have been contacted by multiple groups around the US who are now gearing up to use the model in their research and design work.

GrID: If the impact green roofs have on energy use in a building is as modest as you describe, why would you need to model the green roof? Are there cases where it can/has make/made a significant difference?

Dr. Sailor: As I mentioned previously, if one does not pay attention to the green roof design from an energy standpoint, the roof may perform WORSE than a conventional roof. The tool can help the user avoid such potentially undesirable outcomes and then be used to optimize the design for improving energy performance beyond a conventional design. In the case of a retrofit the existing roof insulation may be significantly lower than current code or the current membrane may be much darker than the 30% reflective baseline that I use in the modeling. In such cases, the actual energy savings of the retrofit may be much larger than that reported directly in the current version of the calculator. Nevertheless, the calculator can be used to optimize the energy performance of the new roof.

GrID: What do you see as the future of green infrastructure?

Dr. Sailor: I think that historically there has been a bit of inertia within the building industry that tends to limit the pace of innovation and application of new concepts. From the perspective of an academic researcher I see great opportunities for applied research to develop new technologies and the data and modeling tools necessary to understand the building performance implications of these technologies. Green roofs and walls are technologies that are both promising, and receiving increased interest in recent years. In order for green infrastructure to reach its full potential, however, it is important to develop the tools and data needed to fully evaluate their many co-benefits.

-Brian Phelps


-Green Roof Energy Calculator

-Mitigation Impact Screening Tool

Chicago Green Roofs: Seven Million Square Feet and Growing

13 11 2009


I got the chance to spend a little bit of time last week with Chicago’s firecracker Commissioner of Environment, Suzanne Malec-McKenna while she was in Nashville for the Nashville Civic Design Centers annual Plan of Nashville event. Suzanne has been in the middle of an astonishing number of Chicago’s environmental bright spots, including the ambitious Chicago Climate Action Plan released in 2008, Chicago Trees Initiative and the very cool Chicago Offset Fund. But what has impressed me the most (and has for a long time) is Chicago’s tremendous growth in green roofs.

It all started in 2001 with the now well-known Chicago City Hall roof weighing in at a modest 20,000 s.f. In June 2008, a short seven years later, Chicago boasted 4,000,000 s.f. of green roof and today, they report that they have hit 7 million s.f. and they are still going. I wanted to find out more about how such an explosion occurs and one of the pieces and parts is related to the success of the green roofs is a Green Roof Grant Program begun in 2005 which has been continued and expanded. An interesting side note is that the popularity and volume of the green roofs across Chicago has also reduced the average installation price of extensive green roof in Chicago has dropped from $25/s.f. to $15/s.f.

As if the incentives of grant incentives aren’t enough, I also noticed that in August 2009, the Illinois Energy Plan provides ARRA funds toward cost-effective energy projects, including green roofs, which meet certain criteria. Illinois has recognized that green roofs provide economic development, carbon capture and energy and maintenance cost savings.

As I looked around at other cities, I found a few more that were engaged in similar incentive programs introduced within the last year: Portland, New York City and Washington DC (List of green roof incentive programs) . Through tax abatement or grants, each of these cities provide an incentive of about $5.00 per square foot through a green roof review process. Portland expects their Grey to Green Program to their current nine acres of green roofs on about 90 buildings to increase over the next five years by another 43 acres. Portland is committing $300,000 in grants in its first fiscal year of the program and is committed to keeping the program going for at least the next five years.

In our neighbor to the north, Toronto started the green roof incentives in 2006 starting with a $10 per square meter subsidy, then raised the subsidy amount to $50 per square meter in order to be more effective. Reports are that funding of $2.4 million dollars for green roof subsidies have been approved for the first five years of the program.

So hats off, Chicago! You are serving as a great example for the rest of North America – in fact, Chicago topped the Green Roofs for Healthy Cities list of top ten cities for both the United States and North America for the past five years.

-Kim Hawkins