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MODULAR GREENROOF TECHNOLOGY:AN OVERVIEW OF TWO SYSTEMS
By Linda S. Velazquez, ASLA Associate
Greenroofs.comPublisher & Design Consultant
Presented at the First Annual Greening Rooftops for Sustainable
CommunitiesConference, Awards & Trade Show 2003, Chicago,
IL
Modular Alternatives to Traditional Greenroofs
In order to better understand modular systems and the many
advantages they offer, we
must 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 to
the 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 .
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.
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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 installation
Time-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;
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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 IrrigationGreenTechIrrigation Lines
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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
companyshistory 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
GreenTechrepresentatives attheir Greening Rooftops for Sustainable
Communities 2003exhibitor 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 considered
an innovative green roof technology that can boost a building's
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 . 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 of
American 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 systems 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.
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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
theGreenGridhorticultural 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 shapes
are 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. GreenGridconducted 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 .
GreenGrid Modules:
Interior of Module Bottom of Module
GreenGrid Product Specifications:
ELEMENT DESCRIPTION Modules:
Standard 2 x 4 and 2 x 2; Depth of modules (two depths) 4 and 8;
Also 2x 2 x 2 depthTwo inch depth modules weigh 10 lbs. wetFour
inch depth modules weigh 15 lbs. wetEight inch depth modules weigh
28 lbs. wet
Pavers:
Length 2 ft., width 2 ft., depth 1.5 in; Paver material -
Recycled automobiletires; 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:
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Wood, composite recycled HDPE/wood (in various colors and
designs), variousothers to order
Plants:Perennials, grasses or shrubs specifically selected for
climate, hardiness zone,color and size.
Applications: Roof Gardens, Intensive and Extensive Greenroofs,
Ground LevelGardens
Case Study: GreenGrid Pilot Project, Beloit, WI, 2001 -
Installation of theGreenGrid at ABC Supply's 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 of
ABCs corporate headquarters. The north garden was designed as
the show garden
and 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.
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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,
GreenTechoffersseveral systems applications, consulting,
design/build and construction services.GreenTechhas the experience,
expertise and systems to provide solutions to the world'sturf,
horticultural and environmental needs, providing advice and
solutions from some of thepremier experts in the
world.GreenTechsystems 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. Whats more, the ITMsystem is the perfect
answer for venues that need to go from sporting event to
rockconcert overnight. A GreenTechgarden 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. GreenTechs Green Roof System
helps you construct a light weight and efficientgreen roof system
on a wide variety of roofs and structures.
GreenTechcan 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, a
non-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.
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GreenTechModule:
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GreenTechProduct 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
GreenTechIntensive Greenroof and Pond Bank Erosion Control
Applications
Case 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
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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.
References
1. www.greenroofs.com
2. www.greengridroofs.com
3. www.abcsupply.com
4. www.westonsolutions.com
5. www.greentechitm.com
