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June 2011
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Various Types of Green Roof Systems Come Together at NYC's 5-Boro Complex By Artie Rollins and John Robilotti, NYC Parks and Recreation Photos Courtesy of NYC Parks and Recreation Introduction
In spring, 2007, the Five Borough Technical Services Division of the New York City Department of Parks and Recreation began a program of installing green roofs of various designs atop the Five Borough Complex on Randall’s Island where it is headquartered. To date the division, with the help of Parks’ Green Apple Corps and others, has installed 24 systems covering over 29,000 square feet (sf) of roof. Combined, the systems installed at Five Borough will, arguably, comprise the fifth largest green roof in New York City.  | NYC Department of Parks and Recreation's 5-Boro Complex. |
Moreover, Five Borough is the only known green roof in the country (quite possibly the world) that features such a vast array of distinctive systems side-by-side for comparison. These systems vary by types of growing medium, depth of growing medium, and plant selection. A sophisticated green roof monitoring system and storm water retention system has also been incorporated into the display, complimenting our working laboratory. Two Distinct Roofs Five Borough’s roof is comprised of two distinct but adjacent rooftops: the main roof over the administrative offices totaling 17,000 sf in area, and a garage roof which totals 25,000 sf. Of the combined 42,000 sf area, 29,000 sf is covered by a green roof. Presently our storm water system services our main roof only and is able to capture all rain water via that which is retained by 9,000 sf of green roof and runoff captured by our 6,000 gallon tank capacity:  | Water storage on the lower roof deck. |
A 1" rainstorm will produce approximately 10,600 gallons of water on the roof of which approximately 5,600 gallons is absorbed by the green roof, with our tanks collecting the 5,000 gallon balance. The water stored in the tanks, which reside on a lower roof deck, is pumped up to the upper main roof where it is used to irrigate the plant material during periods of low precipitation. Between our green roof holding capacity and the storage tanks, based on 40" of rainfall, we eliminate 424,000 gallons of storm water from running off this roof annually:  | Storage tanks irrigate the green roofs when necessary. |
Types of Green Roof Systems
There are many characteristics that make up the different types of green roof systems. First there is the growing medium depth of the green roof. This category is broken into three classifications: intensive, extensive, and semi-intensive. Intensive systems are deeper in soil depth (typically 6" to 12" and greater) and are capable of sustaining heavier rooted plants. This system can be aesthetically pleasing and best resembles a normal garden bed. Extensive systems are shallow in soil depth (less than 6") and are not capable of supporting larger plants, but tend to be easier to maintain.  | Flowering sedums on one of the extensive systems at NYC's 5-Boro. |
A semi-intensive system is the middle ground between intensive and extensive systems. They are usually around 6" in depth (± 25%) and are the most common depth of green roof found at 5-Boro. While the depth of the green roof system often dictates what can be planted, there is still room for examining a variety of plants within each system. There are two main types of plants used at 5-Boro. These plant classifications are sedum and native perennials. Sedum plants are hardy with fleshy leaves. As a succulent, they retain water within their fleshly leaves and therefore are a preferred plant for green roof conditions. Sedums along with other Alpine type plants were typically chosen for use in the extensive green roof systems. Native perennials, with their inherent characteristics of being adapted to their local environment, thereby require minimal care. This category of plants, with their more extensive root system, was typically selected for the semi-intensive and intensive green roof systems. .gif) | Semi-intensive 8" deep Columbia University System with natives. |
The green roof systems installed at 5-Boro consist of varying soil depths and plant varieties; however, another way they differ is the selection of growing medium used. Various types of mineral soil (such as rooflite™), Gaia Soil™, a container growing mix (MetroMix 510), as well as custom growing mediums formulated by 5-Boro, are used. The green roofs constructed at 5-Boro can be placed into two main categories: layered systems and modular systems. A layered green roof is a continuous monolithic system with loose materials that are spread in place or carpet-like materials that are rolled in place. The resulting effect is a seamless fixed green roof installation.  | Layered system at NYC's 5-Boro Complex. |
A modular green roof system consists of self-contained individual units which collectively comprise a complete system. This category provides the additional flexibility of being able to be moved after construction without having to completely dismantle the green roof.  | Modular & alternative systems. |
There are also other non-traditional green roof systems that were installed at 5-Boro including a green wall, container systems, a “walkable” atrium system, as well as planters on top of parapet walls. Layered Systems Gaia™ Soil System The first system installed at 5-Boro (July 2007) was an intensive layered system that is composed of Gaia™ Soil, a low density mixture of compost and recycled expanded polystyrene foam coated with pectin to make it water absorptive. At 12" deep, it is 5-Boro’s most intensive green roof system installed to date. This 20' x 40' system, totaling 800 sf, contains nine native perennial species planted in groupings. With the ability to absorb much water, the system has a wet weight of 25 lbs/sf and a dry weight of 14 lbs/sf. This system was not only the first green roof system installed at 5-Boro but also has the distinction of being the first installed throughout the New York City Parks Department:  | .gif) | 12" GaiaSoil Layered System I at NYC's 5-Boro Complex. |
5-Boro Technical Services Custom Design: "Container Growing Medium System" In June 2008 5-Boro Technical Services experimented with a simplified inexpensive system of its own concoction. A series of five 10' x 12' x 5" deep plots were installed, framed by 6" x 6" wood timber, and consisting only of an EPDM roof protection layer and a growing medium typically reserved for container gardening (Metro-Mix 510). Unlike every other standard extensive green roof Technical Services installed, this monolithic system does not have a drainage layer. Planted in a continuous wave of 3 hardy species of native plants, this "Container Growing Medium System" should provide an indication of how well a green roof can function void of a drainage layer and whether one can flourish in a growing medium not specifically designed for green roofs. Totaling 600 sf, this system was found to have a dry weight of 11 lbs/sf and a saturated weight of 19 lbs/sf. Gaia™ Soil System In July 2008, a second Gaia™ Soil system was installed at a depth of 6" rather than the 12", classifying it as a semi-intensive system. Having all other variables maintained, except for the depth of the soil, 5-Boro was able to analyze and compare the overall performance between the two:  | .gif) | 6" GaiaSoil Layered System II at NYC's 5-Boro Complex. |
5-Boro Technical Services Custom Design: Northeast Wildflower Seed Mix
Another unique layered system, installed in June 2009, was a bed utilizing an economical native U.S. Northeast wildflower seed mix. In an effort to further devise a low cost green roof system, Robilotti developed his own custom growing medium comprised of 80% container growing medium and 20% perlite by volume. In addition to being very economical, it also provides a lighter weight soil with enhanced drainage properties. The dry weight of this system is 15 lbs/sf and a saturated weight is 29 lbs/sf:  |  | U.S. natives at 5-Boro with 20% perlite volume growing media
planted with a Northeast Wildflower Mix System. |
Xero Flor™ System I
In the summer of 2009, the Parks Department received grant money to install one of its largest green roof systems to date (6,250 sf). The system, known as Xero Flor™ from a German based company, is an ultra-extensive (2" deep) monolithic system, which is extremely light weight and has a shallow profile. Among the Xero Flor system's unique characteristics is the pre-vegetated sedum mat along with two lightweight water retentive fleece layers that are used instead of additional growing medium. Parks wanted to examine if a green roof system utilizing sedum could flourish with relatively no growing medium. Robilotti states that this is a tribute to just how hardy sedum are. The sedum mat is comprised of several varieties of sedum primarily selected for their hardiness and drought tolerance. At 8 lbs/sf dry weight and 14 lbs/sf wet weight, this Xero Flor™ system is 5-Boro’s lightest system to date: .gif) | .gif) | Xero Flor System I. |
5-Boro Technical Services Custom Design: “Multi Depth Mineral Soil System” October of 2009 brought on another layered green roof referred to as our “Multi Depth Mineral Soil System.” Although only 400 sf in area, the mineral soil growing medium undulates in depth from 3" to 8". Planted with a combination of sedum plugs and cuttings of several species, this system exhibits the different growth rates at the varying depths of mineral soil. The rolling topography also provides a visual departure and a treat from the far more common flat plane green roof. One can also observe how well the sedum perform as a groundcover in the prevention of soil erosion by keeping the higher ridges from self leveling from the onslaught of rainstorms. The weight per square foot for this system varies considerably.  | The “Multi Depth Mineral Soil System” at 5- Boro. |
Xero Flor™ System II During the summer of 2010, Parks experimented with yet another version of the Xero Flor™ system, the only variable being the addition of a 1" layer of mineral soil. A second grant enabled Parks to install this 6,250 sf system: .gif) | Xero Flor System II. |
This second Xero Flor™ system allowed for the observation of any significant increase in drought tolerance as well as the amount of biomass supported through the addition of the 1" of growing medium. .gif) | A view of both Xero Flor System I and II. |
Vegetable Garden
In the spring of 2010, a 4,000 sf vegetable garden designed by Senior Project Manager Rick Gordon, RLA was installed with collaborative efforts from the Agency’s Weatherization group, Million Trees volunteering, Green Apple Corps, and FedEx’s Energy Smart Outreach program. The soil used for the garden is a custom mix comprised of mineral soil, sterile compost, and perlite. With the intention of maximizing space for planting while maintaining easy access for gardening, the garden was designed and installed with 10 rows of growing soil, 6' wide x 50' long, separated by 2.5' mulch walkways. The garden contains a wide variety of vegetables including tomatoes, peppers, zucchini, yellow squash, string beans, broccoli, corn, lettuce, cucumbers, eggplant and mixed herbs. This year all of our produced vegetables will be graciously donated to a soup kitchen located in the East Harlem section of Manhattan.  | Vegetable farming atop NYC's 5-Boro Complex. |
 | The vegetable farm at dusk on NYC's 5-Boro Complex. |
Columbia University System Later that spring, Columbia University students designed and installed their very own unique 8" layered system atop 5-Boro. With minimal help from the Park’s Department, the students were responsible for all phases of the project from developing the layout of the system and the types of planting and soil to be used, to physically installing all the components into the finished product:  | Columbia University system using 8" deep GaiaSoil™ with natives. |
The Columbia University system consists of GaiaSoil™ and is planted with a species mix from two native plant communities, the Hempstead Plains (Long Island) and Rocky Summit Grasslands (e.g. Bear Mountain) of the New York City region:  | Columbia University System with raised sprinkler. |
Bioroof™
In the fall of 2010, two 250 sf Bioroof™ system test plots were installed. Based out of Ontario, Canada, both Bioroof™ systems are said to be designed to meet the weather conditions of the northeast. Bioroof™ EcoSystem The first type is their high performance green roof system called EcoSystem which has a total height of 10", a saturated load weight of 25 lbs/sf, and a storm water capacity of 1.5 gallons/sf. Because of the late season installation, planting was performed in the spring of 2011 with a seeded application of Bioroof™'s Northern Meadow mix:  | Bioroof™ EcoSystem at NYC's 5-Boro Complex. |
Bioroof™ BioLite System The second system is known as BioLite. At a total height of 4.25" it has a saturated load weight of only 14.25 lbs/sf and a total storm water retention of .65 gal/ft². Also installed during late in the season, a pre-vegetated sedum for the BioLite System: .gif) | Bioroof™ Biolite System at NYC's 5-Boro Complex. |
5-Boro Technical Services Custom Design: Perlite and Metro-Mix 510
In the winter of 2010, Parks experimented with another growing medium of its own design. The soil make up for this system is 80% perlite and 10% Metro-Mix 510 made by SunGro™ of which it contains 15-20% peat moss, 25-35% vermiculite, 40-45% pine bark, and 10-20% bark ash. This 800 sf system, mostly comprised of perlite, is very light yet is able to retain 5-8 times more water than that of untreated garden soil. Wildflowers seeds were planted this past May:  | 80% perlite and 20% Metro-Mix 510, pre-planting. |
Modular Systems
There are five modular green roof systems installed at 5-Boro. All systems are different from one another, with the only similarity being that they were all installed in self-contained units.
In July 2008, there were two tray systems constructed at 5-Boro. Trays for both of these systems were fabricated by 5-Boro's own tradesmen. Planted side-by-side, each 800 sf in overall size, they differ only in the depth of the growing media used accommodated by 4" trays and 6" trays. Both systems use a wide pallet of sedum plants and are planted with approximately 1,520 sedum plugs. 5-Boro Technical Services Custom Design: Tray System I The 4" Tray System I has a dry weight of 14 lbs/sf and saturated weight of 21 lbs/sf:  | .gif) | 4" deep Tray System I at NYC's 5-Boro Complex. |
5-Boro Technical Services Custom Design: Tray System II And the Tray System II has a deeper 6" tray system having a 22 lbs/sf dry weight and 34 lbs/sf saturated weight:
| .gif) | 6" deep Tray System II. |
Green Paks™
Also planted in July 2008, another 20’ x 40’ (800 sf) semi-intensive modular system utilizing bags, instead of trays, was installed known as Green Paks™ by Green Roof Blocks. This modular system is made up of 80-pound prefilled bags of mineral soil. The bag system consists of black woven sacks made of high density polyethylene, prefilled with a proprietary growing medium consisting of 80% expanded shale and 20% composted pine bark. Set atop a root barrier and drainage mat, six slits were cut into each bag where different varieties of sedum plugs were inserted. The dry weight of the system is 16 lbs/sf and the wet weight is 30 lbs/sf:  | .gif) | Green Paks System at NYC's 5-Boro Complex. |
BioTray™ Most modular systems are flexible in that they can be moved after installation if necessary. As an exception to the rule, a BioTray™ biodegradable tray system by Tremco is installed as modular units, but will later turn into a monolithic system as the trays begin to break down as designed. The biodegradable trays made of coconut husk fibers will provide additional organic matter to nourish the mineral soil as they decompose. This system was planted in August, 2008 with three selected varieties of sedum plugs, four per each 17" x 17" x 3" modular tray. The dry weight is 12 lbs/sf and the wet weight is 19 lbs/sf:  | .gif) | Close-up of BioTray biodegradable modular system at
NYC's 5-Boro Complex. |
Green Grid™ In July 2009, another modular system known as the Green Grid™ system as manufactured by Weston Solutions Inc., was installed. This pre-vegetated extensive modular system is unique in that it is preassembled as per the customer’s design specifications and then held at their nursery until it has matured to the point that the customer is ready to take receipt. We specified tray dimension, depth and plant palette for their assembly. The final product results in a mature green roof providing an instant effect. In this design a 4" deep, 2' x 2' modular unit was selected coupled with a colorful pallet and varying textures of sedum, along with the addition of chives which introduced a vertical element:  | Installing the GreenGrid trays are left to right: Summer intern,
John Robilotti, 2 summer interns, 2 NYC Parks Weatherization
Crews and summer intern (in orange). |  | Installing the GreenGrid system at NYC's 5-Boro Complex
and how it looks later more in bloom. |
Robilotti also introduced 2' x 2' salvaged rubber safety surfacing mats here that he painted a tranquil green, which served as another design element while providing a pathway to enter and service the modular system. Other Green Roof Systems
Layered and modular green roof systems are the two main types of green roofs constructed, however, there are many different non-traditional systems installed at the 5-Boro Complex. Some of these systems include: a green wall system, container box planters, and an atrium with existing precast pavers remodeled to accept a green roof.  | Container box planters at NYC's 5-Boro Complex with
Mugo Pine, Sedum sieboldiana and Sedum acre. |
Other atypical systems include a wood and metal parapet wall and an overhead trellis with a surface area of 650 sf, but a roof foot print of only 90 sf. Also, elevated planters were installed which are used to store extra plants material for fill–ins and are being utilized for a community garden for the office staff. Parapet Wall Planters
Our perimeter parapet wall planter surrounds the entire west wing of the roof. The box was fabricated in 2007 out of aluminum sheets by 5-Boro's own sheet metal workers. At 5" deep and 18" wide, this planter is a formidable 530' long ribbon framing the many green roofs it engulfs. Robilotti selected two perennials - blue rug juniper and tufted fescue for their hardiness. The prostrate juniper will cascade over the wall and the fescue adds a vertical element and movement as the long stemmed seed pods sway in the summer breeze. Each spring ornamental sweet potato vines are evenly spaced between these perennials. With their broad lime green leaves and rapid growth rate they add a stark contrast as they flow several feet down the parapet wall. Metro-Mix 510 was chosen here as the growing medium:  | Metal planters on top of parapet walls at NYC's 5-Boro Complex. |
Also, a wood framed parapet atop the atrium parapet wall serves as an ideal location to highlight colorful perennials and annuals:  | Planters on top of wood parapet wall at NYC's 5-Boro Complex. |
Overhead Wood Trellis During the spring of 2008 5-Boro's carpenters were put to work building two overhead cedar trellises. The larger comprises 650 sf and is anchored by 6 - 3' x 3' planter boxes. The second trellis provides an overhead canopy of 220 sf and is anchored by 4 - 3' x 3' cedar planter boxes. The boxes of each trellis were planted with wisteria and trumpet vine which we hope will soon provide an overhead shade canopy for the picnic tables that were strategically placed below. Metro-Mix 510 was also used here as the growing medium of choice:  | Cedar trellises will provide a cool respite for breaks. |
Elevated Planter Boxes 5-Boro carpenters were also put to work in June 2008 building 12 – 2' x 8' raised cedar planter boxes. They have been utilized for multiple purposes including providing community garden space for office staff and as smaller test gardens. They primarily serve, however, as holding areas for extra plants from our various green roof systems as well as for propagating our own sedum plants from cuttings:  | Elevated Planter Boxes hold a variety of plants. |
Green Wall The vertically installed green wall, below, in June 2009 was another first for NYC Parks. Although it is not a true green roof system, it still has many of the same environmental and economical benefits. An ELT Easy Green® wall modular system composed of 20" x 20" plastic grid trays of 2" depth was planted with a patch work of three selected varieties of sedum. These wall panels were constructed in Van Cortlandt Parks’ Bronx Green House during the preceding winter. After taking root the grid trays were mounted on the exterior staircase bulkhead wall of the green roof.  | ELT's Easy Green® System on the staircase wall. |
Atrium Green Roof System Installed in July 2009, the atrium system is Five Borough’s first attempt at a “walkable” green roof. It was installed 4" deep (extensive) with nearly 500 sf of planted area. The plants were carefully selected to tolerate fluctuating amounts of sun and shade caused by the seasonal changes and the angle of the sun coupled with the high atrium walls. Creeping myrtle, red wing phlox, and candy stripe phlox were placed in the non-walkable area, while tall fescue was selected for the high traffic area:  | Atrium “walkable” Green Roof System at NYC's 5-Boro Complex. |
Hydroponics In the spring of 2011, one of our newest additions to the 5-Boro Complex was Hydroponics. This basic system can hold 20 plants, and we have 15 units. The entire system weighs about 125 lbs (without vegetables):  | The new hydroponics system. |
Animal Biodiversity  | Praying Mantis enjoying the Sedum. |
In terms of biodiversity, our green roofs have attracted a wide assortment of wildlife. Included are many species of bees, birds, butterflies and other insects, including the praying mantis on the sedum above, and the butterfly on the walkable atrium greenroof below:  | Butterfly among the flowers of the Northeastern Wild Flower Seed Mix
Green Roof at NYC's 5-Boro Complex. |
And bees also grace our rooftop:  | Overlooking the Atrium Green Roof
from the parapet planters. |
Particularly noteworthy are a pair of red tailed hawks that frequent our green rooftop oasis, occasionally with their breakfast in hand. Presently we have a nesting mocking bird which has laid claim to its own section of our green roof by aggressively fending off all creatures that venture too close, including the two-legged variety.  | Mockingbirds aggressively defend their nest and surrounding area against other birds and animals. They are absolutely unafraid and will attack much larger birds, even hawks. |
Bee Hives In March 2010, the NYC Department of Health and Mental Hygiene lifted a 1999 ban on keeping bees in the five boroughs. We decided to seize this opportunity by installing bee hives the following spring as a complement to our green roof. We now have both solitary bees and honeybees taking up residency on Randall's Island. By welcoming honeybees into our community gardens and neighborhoods, we can increase the yield of what we grow, help secure the sustainability of the world’s greatest pollinators, as well as offer an opportunity to educate adults and school children alike who visit our garden in the sky. The fact that honeybees pollinate nearly 1/3 of our food crops as well as trees, shrubs, flowers, and other flora, coupled with problems that have drastically reduced the honeybee population in the United States only underscores the need for active sustainability practices.  | Honeybees Hives on the roof in NYC. |
Educational Components Many of 5-Boros green roof systems feature informative display boards beside them. The content includes the season and year the system was installed, overall dimensions, type of system, cost/sf, a cross section showing the different layers, descriptive text, as well as a layout plan depicting the planting design complete with pictures and accompanying botanical names of each plant incorporated.  | Display board showing the planting plan for Layered System II. |
These display boards further facilitate the educational attributes of our green roofs. And, presentations and tours are gladly provided by appointment.  | Interpretive signage amongst the plants at NYC's 5-Boro Complex. |
Conclusion
The 5-Boro building rooftop serves as a working laboratory for green roof design and construction, providing the opportunity to share information and knowledge gained with students from schools and universities, interested community groups, trade groups, and governmental agencies in and outside New York City.  | Weather station at NYC's 5-Boro Complex. |
In addition to garnering national interest, these installations have also gained international attention, attracting visitors from England, France, Germany, the Ukraine, and the Netherlands. The New York City Department of Parks and Recreation are expanding their green roof efforts on to other facilities, furthering their understanding and dedication in this field.  | Vegetables, Sedums, and wildflowers. |
Initiated by Chief of Technical Services Artie Rollins, Senior Project Manager John Robilotti has overseen the planning and installation of the green roofs at the Randall’s Island facility. “I’ve witnessed our green roof transform an otherwise inhospitable roof top into a green oasis attracting passive recreation while providing many economic and ecological benefits,” quotes Robilotti.
He further states, “I am convinced that if our Green Roof efforts were carried out on a grander scale throughout NYC Parks and the city, it would go far in reducing the city’s heat island effect while improving water quality by keeping our combined storm/sewer water treatment plants from being over taxed.”  | The beautiful, productive, and educational NYC 5-Boro Complex. |
Artie Rollins and John Robilotti
 | Artie Rollins |
Artie Rollins is Chief of Technical Service, NYC Parks and Recreation. He has a Bachelor in Mechanical Engineering, NYIT 1986 and started in the Parks Department in 1995. Currently, he supervises the Technical Service division which oversees NYC Pools, Trades Shops, Stationary Engineers and Capital Requirements Contracts. Artie started the installation of the Parks Department Green Roof program in 2007.
 | John Robilotti |
John Robilotti is a Senior Project Manager at the NYC Department of Parks and Recreation, where he has held various Design and Construction positions over his 32 years. He holds college degrees in Landscape Architecture, Environmental Science, and Civil Engineering and was responsible for implementing the Parks Department Green Roof Systems at 5-Boro Complex as well as overseeing the installation of “Cool” roofs and conventional roofs citywide. NYC Parks & Recreation
Green Roofs completed (to date June 2011):
29,000 square feet on Randall’s Island, NYC
10,000 square feet at 10 Recreation Centers, NYC. White Roofs completed (to date June 2011): 2010 – 200,000 square feet;
2011 – 50,000 square feet.
For further information, you may contact Senior Project Manager John Robilotti at: John.Robilotti@parks.nyc.gov or Chief Artie Rollins at: Artie.Rollins@parks.nyc.gov.
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