MODULAR GREENROOF TECHNOLOGY: AN OVERVIEW OF TWO SYSTEMS
MODULAR GREENROOF TECHNOLOGY: AN OVERVIEW OF TWO SYSTEMS By Linda S. Velazquez, ASLA Associate Greenroofs.com Publisher & Design Consultant Presented at the First Annual Greening Rooftops for Sustainable Communities Conference, Awards & Trade Show 2003, Chicago, ILModular Alternatives to Traditional GreenroofsIn order to better understand modular systems and the many advantages they offer, wemust address definition, application opportunities, and other reasons to considermodular greenroofs. Depending on whether the greenroof is designed as either anextensive or intensive one, we know greenroofs in general employ either a single-ply ormulti-ply waterproof roofing membrane, with a root barrier if the type of membrane isorganic in nature. A single or multi-layer drainage material follows, with a non-woven,non-biodegradable filter fabric on top of the drainage layer to retain the soil media (Note:Some drainage components include root barrier material in their filter fabric). Insulationis optional although most often recommended, and may be located either 1) above (mostcommon) or below the roof deck; 2) above the roofing membrane (protected membrane,common in Europe) or 3) below the roofing membrane (conventional), as determined bythe architect or contractor. Finally, the engineered substrate/soil media or plantingmedium is determined and placed along with appropriate greenroof plants, according tothe landscape architect/greenroof designer.So, many greenroof assembly designs are possible and available, ultimately determinedby the roof function. Of course, each greenroof location, building, and intended use isunique, and should be designed specifically for the site and project at hand. But in anycase, the greenroofing system is applied on top of the entire roof deck surface, allowingunimpeded drainage and a more even weight distribution over the whole roof. Modularsystems offer the same environmental, cost and energy saving benefits as a traditionalnon-modular greenroof system, while also providing the soothing ecological beauty ofgreenspace on otherwise forgotten and unused impervious rooftops ¹.How is a Modular System Different?With a modular system, the drainage, soil substrate or media, and the plants are self-contained within a lightweight high-density polyethylene (HDPE) module, of varyingdimensions. In effect, these three main components of a greenroof are replaced by afully planted module. When interlocked, they offer continuous roof drainage andcoverage.
Why Consider Choosing a Modular System Over a Standard Multi-LayeredGreenroof?Modular systems offer more overall flexibility for the designer and building owner interms of:Simplicity of Design – the modules are engineered to contain the major elements of agreenroof – drainage, soil media, and plants;Easy Installation - modules can be brought up to the roof via service elevator or crane; GreenGrid™ Module in elevator and during installationTime-Saving Installation – the greenroof plantings can be grown off-sitesimultaneously while the roof is being built or retrofitted until ready for deployment, anddue to the “instant” modular nature of the units, the overall actual roof installation time isgreatly reduced as the drainage layer, soil substrate and vegetative plantings are readyto go and in most cases can be placed directly over the waterproofing membrane;
Off Site Planting - can be grown at any time of the year, and as such, can be placed ona roof at any time of the year because the plants and root systems are alreadyestablished (Note: Most greenroofs are planted/seeded in the Spring or Fall);Instant Roofscapes – fully pre-grown modules provide immediate aesthetic,psychological, economic and ecological benefits for occupants and neighbors; GreenGrid™ GreenTech®Different Substrate/Soil Mix Types – each can be uniquely designed and filled forspecific plant needs to allow a greater diversity of vegetation;Different Soil Depths – each module can vary according to the Master Plan and thedesired plant selection in a given module can reflect pertinent weight load restrictions,e.g. deeper modules can accommodate woody plants and trees over load bearingstructures such as columns and beams;Air and Water Flow – capacity to move air and water is increased, offering greater root-zone airflow and drainage;Irrigation – always optional, yet possible through traditional irrigation lines, drip irrigationand/or rain capture with cisterns at roof or ground level; GreenGrid™ Drip Irrigation GreenTech® Irrigation Lines
Adjustment and Rearrangement after Installation – perhaps the greatest feature ofmodular systems lies in the ability to allow for seasonal design changes and/or roofmembrane repairs or other roof maintenance issues. Physical flexibility is possible forany reason with minimal disruption of other modular plantings or roof membranes.What are the Unique Attributes of the Two Profiled Greenroof Modular Systems,GreenGrid™ and GreenTech®?Each company is certainly unique, offering both similar and different products andservices, to be evaluated as appropriate by the design professional. I will present anunbiased look at both modular systems, with an overview of each of the two company’shistory and philosophy; product specifications; applications and case studies; and futureplans for the greenroof market (Note: All company and product information has beentaken directly from company promotional material and respective websites). Forcomplete information, please contact GreenGrid™ and GreenTech® representatives attheir Greening Rooftops for Sustainable Communities 2003 exhibitor trade show boothsor at their respective websites, listed below under References.Profile #1: GreenGrid™ - “The Natural Choice for Your Roof”Weston Solutions, Inc. (WESTON®), and ABC Supply Co., Inc. (ABC Supply) introducedthe GreenGrid™ System in August, 2001, and, according to their website, is consideredan innovative green roof technology that can boost a buildings bottom line and value.ABC Supply is the largest wholesale distributor of roofing and siding materials, tools, andsupplies in the United States. Founded in 1982, ABC Supply currently has over 200locations in 41 states. Specializing in select product lines, they offer the professionalcontractor (large or small) competitive pricing, superior pick-up and delivery service, andthe highest quality building materials available ³. WESTON® is a leading environmentand redevelopment firm, delivering comprehensive solutions to complex problems forindustry and government worldwide, with an emphasis on creating lasting economicsolutions for its clients 4. GreenGrid and ABC Supply Co., Inc. are trademarks ofAmerican Builders & Contractors Supply Co., Inc., and GreenGrid System is aproprietary technology of ABC Supply with U.S. and international patents pending.WESTON is the sole licensee of the GreenGrid™ System in the U.S.Simplicity of design and flexibility are the hallmarks of the GreenGrid™ roof system. Thesystem was designed by engineering, roofing and horticultural experts, and is theproduct of years of research and testing. Testing of the system’s structural componentsand lightweight recycled plastic materials has been underway since 1997. The result is acomplete green roof solution that is easy-to-install and maintain.
All the components of GreenGrid™ are engineered and provided through their system,including the modules, soil media, plants, irrigation system, edge treatments, pavers,water features and furniture. After the property owner and/or designer consults with theGreenGrid® horticultural experts to select appropriate greenroof plants for the site, themodules arrive fully planted and ready for installation. Modules are available in threedepths: 2”, 4” and 8” and standard sizes of 2’ x 2’ and 2’ x 4’. Various custom shapesare also possible.In a 2000 study conducted for the City of Chicago, WESTON estimated that greening therooftops of all city buildings in Chicago would result in nearly $100 million of annualenergy savings. Peak demand would be cut by 720 megawatts – the equivalent ofseveral coal-fired generating units or one small nuclear power plant. GreenGrid™conducted temperature studies on their 4” and 8” Modules in August 2002, showinghighly reduced roof readings when greened – stormwater performance evaluations havealso been studied and analyses are available on the GreenGrid™ website ².GreenGrid™ Modules: Interior of Module Bottom of ModuleGreenGrid™ Product Specifications:ELEMENT DESCRIPTION • Modules: Standard – 2’ x 4’ and 2’ x 2’; Depth of modules (two depths) – 4” and 8”; Also 2’ x 2’ x 2” depth Two inch depth modules weigh 10 lbs. wet Four inch depth modules weigh 15 lbs. wet Eight inch depth modules weigh 28 lbs. wet • Pavers: Length – 2 ft., width – 2 ft., depth – 1.5 in; Paver material - Recycled automobile tires; Paver Colors - Forest green, black, brick • Drainage/root barrier medium: Geotextile • Soil media: Proprietary mixture consisting of organic and inorganic material • Drip irrigation system: Black polystyrene tubing • Edge treatments:
Wood, composite recycled HDPE/wood (in various colors and designs), various others to order • Plants: Perennials, grasses or shrubs specifically selected for climate, hardiness zone, color and size.Applications: Roof Gardens, Intensive and Extensive Greenroofs, Ground LevelGardensCase Study: GreenGrid™ Pilot Project, Beloit, WI, 2001 - Installation of theGreenGrid™ at ABC Supplys corporate headquarters in August, 2001 gave ABC theopportunity to turn undeveloped and unattractive roof space into useable and strikinggardens. The rooftop gardens are enjoyed daily by the employees of ABC Supply andthe ongoing research capability provided by the green roof will aid in offering all clientsproven rooftop plant selections, concrete energy savings data, and stormwater retentiondata. The project was planned as a ‘showcase green roof’ and both intensive andextensive GreenGrid™ modules were installed on the north and south roof portions ofABC’s corporate headquarters. The north garden was designed as the “show” gardenand the south designed as both a show and research green roof. The research area isused to experiment with the hardiness tolerances of potential rooftop plant species; toquantify the GreenGrid™ insulating characteristics and stormwater managementfeatures; and to test other potential system components. GreenGrid™ applied at the ABC Headquarters in Wisconsin.
Profile #2: GreenTech® - “Roof Garden System”GreenTech® has offices in the United States and the U.K. and introduced the ITMmodules to the sports market in 1995. The Roof Garden System had been sinceresearched and became available in 2002. Company philosophy seeks to produce roofgarden products that encourage the management of stormwater runoff, erosion controland general environmental well being. According to their website, GreenTech® offersseveral systems applications, consulting, design/build and construction services.GreenTech® has the experience, expertise and systems to provide solutions to the worldsturf, horticultural and environmental needs, providing advice and solutions from some of thepremier experts in the world. GreenTech® systems are equally at home in college footballstadiums, championship golf courses and city rooftop gardens.The modular design offers an infinite variety of configurations - from raised plots thatenable handicapped gardeners to gently undulating green spaces. What’s more, the ITMsystem is the perfect answer for venues that need to go from sporting event to rockconcert overnight. A GreenTech® garden is tremendously flexible -- it can be placed ona patio, raised off the ground for easy access or for gardeners with limited mobility, andcan support a wide variety of plants, even if they require different types of soils.Healthy roof gardens and intensive greenroofs are possible without the load or drainageissues. GreenTech’s Green Roof System helps you construct a light weight and efficientgreen roof system on a wide variety of roofs and structures.GreenTech® can work hand in hand with the property owner and greenroof designer torecommend appropriate soil mixes and plants, but ultimately the client is free to selectand purchase both as desirable. GreenTech offers the flexibility of selecting either pre-planting their modules off-site or assembling on-site at the discretion of the client. Built-in drainage channels allow water to flow through the soil into the open channels anddirectly to roof drain outlets. The contained environment and excellent drainage developand maintain healthier plants.At the same time, high-density polyethylene module protects the roof surface from rootinfiltration and damage to the roof membrane. Modules have a minimum 8” depth, butcan be planted to any depth. Fold up or custom height fences are attached and canincrease or vary soil substrate depths. Depending on the type of soil mix selected, anon-woven filter fabric may or may not be required.Modules measure 46” square, yet the trays can be cut on site to accommodate odd roofcontours. Modules interlock on plastic foot-locator pads that have knobs on each of thecorners, so four modules are joined by one foot-locator pad 5.
GreenTech® Product Specifications:Applications: Roof Gardens, Intensive Greenroofs, Accents on Extensive Greenroofs,Athletic Field Systems – Multi-use Venue and Permanent Fields, Erosion Control, GolfSystems – Tee, Green and Portable Turf Nursery GreenTech® Intensive Greenroof and Pond Bank Erosion Control ApplicationsCase Study: Residential Intensive Greenroof over condo garage in Chicago, IL,2002 - Dan and Naomi Sachs were looking to create green and garden space on theirback patio for their young children. Living in downtown Chicago, green space is at apremium in the city, so they decided to bring the park home. Because the Sachs wantedan accessible and useable roof garden, the GreenTech System was a perfect fit. Thesystem was able to comply with strict weight requirements imposed by the condo
association, and the Sachs like the fact that their back yard could move with them if theyever moved. Native and drought tolerant plantings, including flowering perennials, willsoon be added to enhance the bluegrass sod play area. From start to finish, this projectwas completed in two days.References1. www.greenroofs.com2. www.greengridroofs.com3. www.abcsupply.com4. www.westonsolutions.com5. www.greentechitm.com