FXCollaborative Podium: Follow the Water

Follow the Water

green roofs and the promise of a blue future

Peter Olney | FXCollaborative

Follow the Water

green roofs and the promise of a blue future Peter Olney, AIA, LEED AP BD+C, GRP, Senior Associate, FXCollaborative

For the six-year period from January 2009 through December 2014, I spent an inordinate amount of time on the roof of the Javits Center, a 1.8-million-square-foot facility covering six contiguous New York City blocks on the western edge of Manhattan, with its expansive views of the ever-present Hudson River to the west and a Hell’s Kitchen neighborhood starting its own transformation to the east.

It was a few years earlier, in 2005, that FXCollaborative Architects of New York and Epstein of Chicago formed a joint venture entity to provide architectural services for the complete renovation of the then 30year old Javits Center, known in the industry as the United States’

busiest convention center. When I joined the architectural design team following the completion of the Design Development phase, my primary responsibility was to lead a sub-team of architects and specialty consultants with the sole purpose of transforming an obsolete, and increasingly detrimental, convention center roof into a positive asset that not only addressed the obvious existing condition issues of water infiltration and minimal insulation, but also strove to address larger neighborhood, regional, and global environmental issues.

Designed in 1979 by I.M. Pei and James Freed of I.M. Pei and Partners, the Javits Center opened in 1986

and currently hosts over 175 events each year including multi-day trade shows, conferences, conventions, and single-day special events. With the convention center showing its age after 30 years of use (Figure 1), the challenges facing the FXCollaborative Epstein team included designing the repair, restoration, or replacement of the exterior envelope, mechanical systems, exposed architectural concrete, and interior public spaces, all the while respecting and reinforcing the integrity of the original design, keeping the convention center operating throughout the duration of the renovation work, and improving the building’s relationship with the surrounding community. The incorporation of an extensive-type

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Follow the Water: Green Roofs and the Promise of a Blue Future

Figure 1

Aerial view looking north of existing Javits Center Roof prior to start of the center’s 2010 - 2014 renovation. Pier 76 and the Hudson River are directly west of the Javits Center.

green roof was identified very early in the design process as a key element to address the host of challenges present in the overall renovation of the Javits Center facility. With the architectural design vision for the renovation work in alignment with the goals of the client team and the building operations team, the New York Convention Development Corporation (NYCCDC) and the New York Convention Center Operating

Corporation (CCOC) respectively, my subteam set about incorporating a 6.75-acre, or 294,000-square-foot, green roof, the second largest green roof in the United States, into the design of the new 14.25-acre, or 620,000-square-foot, roof and into the renovation project as a whole. (Figure 2) Since convention center visitors typically occupy the building more than330 days per year, the construction of the $463 million renovation project, managed

by AECOM Tishman, proceeded in 12 sequential phases over a 5-year period from 2010 through 2014.

Peter Olney | FXCollaborative

Figure 2

The green roof is only one of the many sustainable strategies in the overall Javits Center renovation project. The project was awarded LEED Silver certification in October 2015.

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Follow the Water: Green Roofs and the Promise of a Blue Future

Figure 3

Aerial view of New York City’s Central Park and the surrounding urban density.

Image © Pictometry

Managing Stormwater While green roofs in urban settings are increasingly becoming known to the general public for performing multiple sustainable functions, including promoting biodiversity, noise attenuation, capture of airborne pollutants, aesthetic enhancement, and increased waterproof membrane durability among other benefits, this paper will concentrate on the impact green roofs have on the liveability, health, and sustainability of cities through their ability to significantly reduce the volume of stormwater runoff from building roofs as compared to the majority of traditionally designed roofs typically found across the

United States. As demonstrated by the performance of the completed Javits Center roof renovation over the past 32 months, even the thinnest and lightest type of green roof system, known in the green roof industry as an extensive green roof, can provide exceptional results in its role as an efficient and effective stormwater infrastructure strategy.

Without implementation of innovative infrastructure solutions, increased levels of stormwater runoff will continue to pollute local waterways and contribute to habitat degradation, beach closings, and swimming and fishing advisories. Green roofs can counteract these adverse effects by limiting the amount of precipitation that leaves a building site, and in the case of New York City, help reach the goal of opening 90% of City’s waterways to recreation.1

1 New York City Sustainable Stormwater Management Plan 2008, p. 62.

Peter Olney | FXCollaborative

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Figure 4

Diagram of combined sewer system operation during dry and wet weather conditions.

Untreated sewage is discharged into adjacent waterways during wet weather events when the publicly owned treatment works (POTW) at capacity. Source: US Environmental Protection Agency.

Looking back at the same six-year period of my involvement in the Javits Center renovation project, 314 inches, more than 26 feet, of precipitation landed on the streets, sidewalks, roofs, and parks of New York City, with a recent annual average precipitation total in excess of 48 inches.2 These recent annual precipitation totals in New York City are only a few inches less than the totals in Seattle, Washington and Portland, Oregon, two cities known nationally for significant quantities of rain. Precipitation in urban areas such as New York City, more often than not, will fall onto an impervious surface (Figure 3) and ultimately will rely on a city’s stormwater system to safely manage the flow, treatment, and release of this water. In the natural water cycle, water is constantly moving between the oceans, atmosphere, land, and rivers as it changes states between a liquid and a gas. Water, in its liquid form, whether in oceans or other waterbodies, is constantly evaporating and will become a gas, in the form of water vapor, in the earth’s atmosphere.

This atmospheric water vapor will eventually condense, changing back to a liquid, and return to earth in various forms of precipitation, either rain, sleet, hail, or snow, depending on temperature levels. Precipitation that reaches the ground in non-urban areas tends to soak into the earth to recharge natural aquifers or flow across the surface of the earth as runoff reaching nearby streams, rivers,

2 https://www.weather.gov/media/okx/Climate/CentralPark/monthlyannualprecip.pdf, p. 4.

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Follow the Water: Green Roofs and the Promise of a Blue Future

ponds, or lakes. In heavily built-up areas, large swaths of impervious surfaces disrupt the natural water cycle by generally creating more runoff than would occur if the area had not been developed. As the natural water cycle occurs across large regions of the globe, precipitation, whether it lands on public or private property, quickly becomes part of the public realm. While a common tendency to keep a building interior dry and comfortable for its inhabitants is to shed water off of a roof and away from a building, the rejected stormwater, in significant quantities, will adversely affect the local environment, and therefore must be managed.

population of about 40 million people.3 Unfortunately, too often stormwater will periodically overwhelm the combined sewer system, even during what is considered a moderate rain event, resulting in the discharge of untreated sewage into adjacent rivers and harbors. (Figure 4) These discharges are known as combined sewer overflows (CSOs). And while sewer back-ups and street flooding are localized examples of the negative impact to public health and safety when the capacity of combined sewer systems is temporarily exceeded, it is the large-scale regional environmental impact of CSOs on the quality of local waterbodies that is of higher concern.

Waterway Pollution

An architect’s concern about the water quality of a city’s rivers and harbors may at first appear distant from the day-to-day work involved in the architectural design of buildings, but it is the impact that water has within the built environment that requires more consideration. For example, a recent 1.2-inch rainfall event recorded in New York City overnight on April 3-4, 2017, resulted in an advisory for recreational boating, wading, and fishing activities from the Riverkeeper organization, New York’s clean water advocate. The advisory was issued due to an Enterococcus Count, the EPA’s preferred indicator for sewage contamination, of 1,723 cells/100 mL in the Hudson River at West 145th Street, about 5 miles

A common solution, developed in the 1880s and used until the 1940s, to control the movement and treatment of water in communities around the globe, including portions of New York City, is the deployment of a combined sewer system, where the network of underground piping is tasked with handling both wastewater and stormwater. While the construction of new combined sewer systems has been curtailed for the past 70 years, this type of sewer system remains in use in many places around the United States. According to the US Environmental Protection Agency, combined sewer systems are utilized in approximately 772 US communities with a total

3 https://www3.epa.gov/region02/water/sewer-report-3-2011.pdf, p. 3.

Peter Olney | FXCollaborative

Figure 5

Artist’s concept illustrating water’s journey through interstellar space to our solar system.

Image courtesy of Bill Saxton, NSF/AUI/NRAO.

north of the Javits Center.4 According to local researchers, New York City will experience at least one CSO occurrence per week over the course of a year.5 At such consistent rates, the affected waterways are under stress to maintain acceptable levels of cleanliness. Polluted waterbodies

are the antithesis to New York City’s desire to take advantage of the waterfront for recreation and supporting residential and commercial development opportunities.

Water Is Life But first, why is water so important?

Simply put, water is essential to human life and, looking beyond Earth, at the scale of the Universe, scientific research conducted at the University

4 https://www.riverkeeper.org/water-quality/hudson-river/nyc-hudson-bergen/north-river-stp/ 5 http://water.columbia.edu/files/2014/04/Green_Infrastructure_FINAL.pdf, p. 10.

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Follow the Water: Green Roofs and the Promise of a Blue Future

Schoharie County

A l bany County NEW YORK

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lu m bi a Co u the Shandaken Tunnel, the Catskill Aqueduct, and n ty the Kensico and Hillview Reservoirs • Provides 40% of the city’s water supply • Supplies 600 million gallons per day

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lakes, the Croton Aqueduct, and the Jerome and Central Park Reservoirs • Provides 10% of the city’s water supply • Supplies 180 million gallons per day

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Figure 6

Fresh water is supplied to New York City from three distinct watersheds with a total of 19 reservoirs and three lakes with a total storage capacity of 550 billion gallons. Source: NYC Department of Environmental Protection.

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Peter Olney | FXCollaborative

Image

Warning signs along New York City’s waterfront are a common reminder of the threat posed to human well-being from combined sewer overflows.

Image courtesy of James Nova.

of Michigan has found that up to 50% of the water on Earth was originally formed in interstellar space prior to the formation of our sun and solar system.6 (Figure 5) While water’s

age is thought-provoking in its own right, water is a critical part of healthy, vibrant communities, and although water covers more than 70% of the Earth’s surface, less than 1% is fresh water and suitable for human use. Water on our planet is both prevalent and scarce, too much water in one region results in floods while not enough water in another region creates drought, and it is apparent

6 http://www.ns.umich.edu/new/releases/22401-the-water-in-your-bottle-mightbe-older-than-the-sun

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Follow the Water: Green Roofs and the Promise of a Blue Future

that sources of freshwater, such as lakes, rivers, and aquifers, throughout the world are under stress partly due to pollution from stormwater runoff.

At the regional scale, the historical establishment and growth of cities has relied on the existing ecosystems both within and beyond their political boundaries for their well-being and continued prosperity. In terms of their relationship to water, cities founded adjacent to waterbodies rely on rivers, harbors, and oceans for industry, transportation and recreation, while nearby rivers and lakes are often used as sources of freshwater. Present-day New York City covers approximately 305 square-miles of land where the Hudson River meets New York Bay and the Atlantic Ocean. Situated at the edge of one of the world’s largest natural harbors, the five boroughs of the City inhabit four distinct land masses separated by major waterways and combined have nearly 600 miles of coastline, all contributing to New York City’s position as one of the world’s preeminent waterfront cities. New York City, with a population of more than 8 million residents, relies on receiving its fresh water from a reservoir system stretching a distance of over 50 miles from the City’s northern limits. (Figure 6) With a Midtown location convenient to all of Manhattan’s cultural and recreational offerings, the Javits Center is situated at the southern reaches of the Lower

Hudson River watershed. The Javits Center, within 100 feet from the eastern edge of the lower Hudson River, finds itself front and center to the body of water most affected by how it, and its neighboring buildings, manage stormwater. Since great effort is expended to ensure that freshwater is readily available for use by residents and visitors alike, it is equally vital that the water returned to the environment after use does not threaten the City’s, or any other communities’, water supplies or waterbodies.

Governmental Action Green infrastructure is key to controlling stormwater. Examples of green stormwater infrastructure include green roofs, cisterns, permeable pavers, bioswales, rain gardens, rain barrels, and porous concrete and asphalt. Key to preventing pollution from entering local waterways is decreasing the volume of water entering the combined sewer system.7 As explained in the City of Chicago’s Green Stormwater Infrastructure Strategy, “green stormwater infrastructure utilizes an underlying philosophy of pollution prevention and the premise that it is better to prevent pollution that to treat it”.8 The United States Environmental Protection Agency (USEPA), along with a number of state agencies, including New York State, have endorsed the use of green infrastructure for attenuating

7 https://www3.epa.gov/npdes/pubs/inflwred.pdf 8 https://www.cityofchicago.org/content/dam/city/progs/env/ ChicagoGreenStormwaterInfrastructureStrategy.pdf, p. 17.

Peter Olney | FXCollaborative

stormwater through runoff reduction and have worked to establish a framework to promote the understanding and adoption of this low impact approach. While the majority of green infrastructure solutions in urban areas must be implemented on limited public land or within already congested public right-of-ways, the roofs of existing and new buildings represent a significant and substantial amount of underutilized space in which to unleash the advantageous potential of green roofs. For example, in New York City, rooftops comprise 28% of the City’s total impervious surface area,9 roughly 60 square-miles, making roofs both a major source of the City’s stormwater management challenges as well as an untapped means to offset that impact through sustainable building strategies.

New York City projects with high sustainability aspirations do not occur in a vacuum. In the case of the Javits Center, there are city, state, and federal influences. At the federal level, the United States government has recently taken steps to promote green stormwater infrastructure design and construction. Over the course of the last six years, green infrastructure has increasingly been part of the strategy devised by national and local government agencies to comply with the regulations in the Clean Water Act of 1972. In a USEPA memorandum issued in October 2011, the agency states that it “strongly encourages

the use of green infrastructure and related innovative technologies, approaches, and practices to manage stormwater as a resource, reduce sewer overflows, enhance environmental quality, and achieve other economic and community benefits.”10 Government regulations have a significant impact on the financial allocations to green stormwater infrastructure as studies have shown that the majority of cities are committed to action in order to honor current federal consent decree agreements.11

Javits Center Green Roof Advanced and detailed planning is required to bring a green roof project to realization. The benefits of an extensive green roof that were attractive to both the Javits Center client team and the FXCollaborative Epstein design team included increased waterproofing membrane durability, noise reduction, energy efficiency, stormwater management, and urban heat island effect reductions.

Also of utmost importance to all involved was aesthetic improvement.

As Bruce S. Fowle, FAIA, LEED AP, of FXCollaborative Architects, the Partner-in-Charge of the Javits Center renovation project explains, The benefits of installing a green roof at the Javits Center include the reduction of storm runoff volume and peak flow.

It will conserve energy by moderating temperatures on the roof and lowering the temperature of the air being drawn

9 http://www.nyc.gov/html/dep/pdf/green_infrastructure/NYCGreenInfrastructurePlan_ LowRes.pdf, p. 53.

10 https://www3.epa.gov/npdes/pubs/memointegratedmunicipalplans.pdf 11 https://www.cityofchicago.org/content/dam/city/progs/env/ ChicagoGreenStormwaterInfrastructureStrategy.pdf, p. 19.

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Follow the Water: Green Roofs and the Promise of a Blue Future

Image

Notifications and warning signs from New York City’s Department of Health are familiar to many of the City’s beachgoers. Wet weather events with a little as 1/2 inch of precipitation often results in beach closures due to combined sewer overflows. Source: NYC Department of Health.

into the rooftop HVAC units during the cooling season, while simultaneously helping to reduce temperature extremes inside the building. The green roof also adds the aesthetic value of urban open space—the fifth facade of the building that will be seen and appreciated from emerging adjacent high-rises.

The FXCollaborative/Epstein design process included extensive studies to evaluate the existing condition of all building systems, the user experience, the operational requirements, the adjacent urban influences, and

energy reduction opportunities. With guidance from the project’s roofing consultant, Rainer Gerbatsch of Commercial Roofing Solutions, the design team selected a 2-inch-thick, pre-vegetated sedum mat system, a lighter system than a conventional roof with pavers, which proved to be a cost-effective solution since it avoided the requirement for structural reinforcement of the existing steel space frame and acoustical metal deck structural system. Of all the layers that comprise a green roof, the depth

Peter Olney | FXCollaborative

Image

With improvement in the water quality of New York City’s waterways, more residents and visitors are seeking out opportunities for recreation on the City’s major rivers.

Image © Bernie Ente

of the growing media has the largest impact on the weight of the overall system. The structural analysis of the existing roof structure determined that the maximum saturated weight of the total green roof system needed to be 18 pounds-per-square-foot or less to avoid new structural reinforcement.

The selected pre-vegetated mats, the Xeroflor XF301+XT sedum system, satisfied the weight parameter while providing a system with a proven

performance record. During the green roof selection process, the design team toured a 450,000-square-foot Xeroflor XF301+XT installation at Ford Motor Company’s River Rouge Plant in Dearborn, Michigan, to see first-hand how the four-year-old green roof was performing and to discuss the lessons learned experience from the point of view of the suppliers, installers, and operators.

Green roofs, although not overly complex, involve more than just adding vegetation to the roof surface of a building. Green roofs are generally comprised, from top-to-bottom, of vegetation, engineered soil,

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Follow the Water: Green Roofs and the Promise of a Blue Future

Metal Retainer Irrigation Line

CFA Flashing

Sedum

Prefabricated Expansion Joint

Pre-cultivated Vegetation Mat w/ Integrated Water Retention Mat

Concrete Pavers 24x24x2

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Figure 7

Section detail of the Javits Center roof.

a water retention mat, a drainage mat, a root barrier, waterproofing, and a engineered roof structure.

(Figure 7) Green roofs are categorized as either intensive, semi-intensive, or extensive, based upon the depth of the engineered soil, typically known as the growing medium. Intensive green roofs have more than 6 inches of growing media while an extensive green roof will have less than 6 inches of growing media. A semi-intensive green roof is one for which a quarter of the green roof area contains more or less than 6 inches of growing media. As the growing medium depth increases, there is a corresponding increase in weight, access, plant diversity, irrigation requirements, design flexibility, maintenance, initial

cost, and replacement cost. Through the use of one of the thinnest green roof systems available, the construction and maintenance costs associated with the new Javits Center green roof where kept to a minimum. (Figure 8) Green roofs affect the amount of water runoff in three ways: water holding or retention, slowing water flow or detention, and water vapor transmission or evapotranspiration.

Evapotranspiration occurs when precipitation falling onto a green roof is absorbed by the vegetation and then is released as water vapor through the leaves of the plant. The pre-vegetated mats for the Javits Center were grown in Central New York in the year prior to their installation in New York City and included 11 different varieties of sedum, a flowering succulent plant.

Retention and detention both occur

Peter Olney | FXCollaborative

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The construction activities at the Javits Center included metal deck assessment and the installation of the temporary waterproofing membrane, lightweight insulating concrete, final waterproofing membrane, pavers, growing medium, and pre-vegetated mats.

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Follow the Water: Green Roofs and the Promise of a Blue Future

Image

View of Javits Center roof looking north.

in the growing medium, retention mat, and drainage mat layers. By promoting evapotranspiration, providing stormwater storage capacity, and delaying stormwater release into the combined sewer system, a green roof is effective in reducing both the volume and rate of runoff leaving a specific site. The exact hydrological performance of green roofs, however, is dependent on a large number of variables such as roof slope, drainage layer design, substrate depth and composition, and plant types. With so many variables affecting green

roof performance, present and future research efforts will be key to confirming and documenting the influence each individual component has on overall performance.

Green Roof Monitoring Demonstrating successful green roof implementation that is coupled with conclusive scientific research is a compelling way to ensure an increase in green roof installations. Fortunately, the FXCollaborative Epstein team had the opportunity to assist with the integration of a research effort jointly proposed by the Sustainable Water Resource Engineering Laboratory

Peter Olney | FXCollaborative

Figure 9

View of weather station installation at North roof of the Javits Center following placement of green roof system.

at Drexel University and Department of Civil Engineering at the Cooper Union for the Advancement of Science and Art. Supported by funding from the Convention Center Development Corporation to conduct a Roof Monitoring Study at the Javits Center and directed by lead researcher, Dr. Franco Montalto, a professor at Drexel University’s College of Engineering, the Drexel University/ Cooper Union team is investigating three performance areas: changes to the microclimate, energy performance,

and stormwater runoff.12 The monitoring equipment includes a handheld infrared camera, three Parshall flumes, three weighing lysimeters, four weather stations, and fifteen soil sensors. (Figures 9) The infrared camera is being used to analyze exterior and interior temperature variations at 16 locations on the roof.

A Parshall flume is a device used to continually measure the flow of water at the low point of each of the 2,000-square-foot green roof areas.

The weighing lysimeter is a sensitive scale installed below the vegetative and growing media layers to detect changes in the moisture content to calculate the amounts of evaporation

12 http://drexel.edu/now/archive/2013/May/Green-Roof-Javits-Center/

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Follow the Water: Green Roofs and the Promise of a Blue Future

NY receives

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175 events

per year

per year

30-year-old

existing building

26% energy

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330 days

square-foot facility

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green roof...

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28%

1.8 million-

per year

gallons per year of stormwater runoff prevented

Rooftops comprise of NYC’s impervious surface area

5-year

renovation period

LEED

Silver Rating

81% of precipitation retained by green roof

Peter Olney | FXCollaborative

and plant transpiration over time. The stormwater runoff research is focused on an analysis of the green roof performance in terms of capturing precipitation and reducing the peak stormwater discharge from the roof.

The results of the rainfall runoff analysis to date prepared by the Drexel University/Cooper Union team have exceeded expectations. The research indicates that approximately 81% of the precipitation that landed on the green roof was retained by the green roof system and did not become water runoff that would otherwise flow down the roof drains and enter New York City’s combined sewer system.13 The research also provides insight on how the percentage of retention varies based upon the amount of precipitation that falls during an individual occurrence. While the results vary from weather event to weather event depending on amount of precipitation, the duration, and time between weather events, for the purpose of analysis, the rain events are classified as either heavy, medium, or light. Based upon the 32 rain events measured on the Javits Roof in 2015, heavy rain events with more than 1/2 inch of precipitation are 68% retained, medium rain events with more than 1/4 inch but less than 1/2 inch of precipitation are 77% retained, and light rain events with less than or equal to 1/4 inch of precipitation are 95% retained. With this data,

it is calculated that during a 12-month period, the Javits Center green roof is functioning to prevent up to 7 million gallons of stormwater runoff.14 It is anticipated that, as the green roof planting matures and is properly maintained, the Javits Center green roof’s ability to retain precipitation will improve. Publication of the rainfall runoff monitoring study prepared by the Drexel University/Cooper Union will be completed following the collection and analysis of additional data.

Conclusion In the last two and a half years since its completion, the Javits Center green roof has captured the imagination of those ultimately in charge of its care, the CCOC, and it is heartening to see the wide-ranging benefits of the Javits Center green roof expand through the addition of bee hives, public tours by appointment, and a live video feed on the Javits Center website. The overall renovation project earned a LEED (Leadership in Energy and Environmental Design) Silver rating from the US Green Building Council with the green roof system contributing to an energy consumption savings of 26% over the pre-renovation performance of the building and the reduced heat island effect by covering 62% of the non-skylight roof area.15 Cities benefit when architecture

13 http://www.javitscenter.com/media/97557/7674_ javits_sustainability_report_060617.pdf, p. 13.

14 Ibid.

15 https://www.usgbc.org/projects/jacob-javits-convention-center

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Follow the Water: Green Roofs and the Promise of a Blue Future

Image

View on the completed Javits Center roof.

Peter Olney | FXCollaborative

Image

View of completed Javits Center roof looking north.

successfully serves as the mediator between the natural and constructed environments. In cities throughout the United State and the world, greater implementation of green roof projects will help improve the water quality of local waterbodies and create improved opportunities for enjoyable waterfront-related recreation and development. Considering that the history of vegetated roofs throughout the world is well documented, green roof scientific research is increasingly becoming available, and successfully completed green roof project abound,

it’s time for green roofs to be considered the leading sustainable stormwater infrastructure strategy for metropolitan areas in order to ensure a blue future for all.

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Follow the Water: Green Roofs and the Promise of a Blue Future

Peter Olney | FXCollaborative

Peter Olney joined FXCollaborative in 1995 and was promoted to Senior Associate in 2008. During the course of his 21 years with FXCollaborative, he has gained extensive expertise in the design, coordination, and execution of large-scale buildings in urban settings. From 2007 to 2014, Peter served as the chair of the FXCollaborative Standards/ Quality Assurance Working Group, completing the development and implementation of office project standards and procedures.

In addition to his project work, Peter is active in the management of the firm’s Commercial/ Residential practice.

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