By Steven W. Peck, GRP, HASLA
Published in the August 2010 issue of Today’s Facility Manager
Because green roofs have a significantly longer life expectancy than conventional roofs, maintenance is a key factor in keeping these roofs functioning at their best, and facility managers (fms) play a key role in making this happen. But when green roofs are kept at their optimal performance level, their benefits include producing energy savings by reducing air conditioning and heating costs, capturing stormwater, and providing visually appealing features on a building.
A Green Thumb
All roofs, green or conventional, require regular maintenance. One of the main causes of plant failure on green roofs is the lack of proper maintenance over the first five years.
Maintenance is crucial to a green roof’s ability to live up to the claim that it will prolong the life of a waterproofing membrane up to 40 years. Creating a detailed maintenance plan during the design of the green roof is critical to short- and long-term success.
A five year maintenance contract should be established by fms prior to the completion of the project. On very large projects, maintenance may be required on some sections prior to completion of others.
Green roofs can be categorized as intensive or extensive, depending on the depth of growing medium. An extensive roof is characterized as having a growing medium depth of 6″ or less (it is also characterized by its lower weight, lower plant diversity, cost, and maintenance). Intensive green roofs have more than 6″ of growing media and have higher plant diversity, higher weight, cost, and maintenance.
After the establishment period has ended, extensive green roofs generally require two or three inspections per year for weeding. This regularity also helps to ensure the drains are clear. Meanwhile, intensive green roofs may require weekly maintenance for irrigation scheduling, pruning, and replanting.
Irrigation systems will require periodic maintenance and may have to be emptied prior to the winter months. Similarly, the waterproofing assembly will require periodic maintenance and repair, especially around the parapet walls and any areas with roof penetrations (such as drains and shafts).
Hiring a landscape contractor with experience working on green roofs is essential for fms. Maintenance contracts often have performance measures such as maintaining healthy plants. This is something that should be requested in advance by the fm.
Repairs to a green roof are more complicated than on a traditional roof assembly. Roof replacement strategies should also be included in the maintenance plan, setting out procedures for the storage of—and care for—vegetation and growing medium during repairs to the waterproofing membrane. Space and loading capacity permitting, the displaced overburden can be moved onto other areas of the roof and then returned to the original site.
Fire Safety Guidelines
In the past, certain groups have raised concerns as to the risks of fire safety with regard to green roofs. As a result, more guidelines with an emphasis on maintenance and management to optimize performance over the long-term are being developed for the North American green roof market.
Officials from Green Roofs for Healthy Cities (GRHC), the industry association promoting green roof and wall technologies in North America, and the Single Ply Roofing Industry (SPRI) Inc., the trade association representing the manufacturers of commercial roofing systems and component suppliers, announced that, as of February, 2010, the American National Standards Institute (ANSI) has accepted the VF-1, Fire Design Standard for Vegetative Roofs as an American National Standard.
This document was created to provide a design and installation reference for roofing professionals to help eliminate the risk of fire on vegetative/green roofs. The new standard should help to open the doors to better design practices in the industry and allay overblown concerns about fire on green roofs. The main elements of the guide have now been accepted by the International Code Council.
Green Roofs And Utility Conservation
The future ability of green roofs to retain the positive benefits of vegetation in cities will hinge directly upon the wise use of water resources in an increasing number of water stressed markets. Pioneering research by Dr. Paul Mankiewicz of the Gaia Institute in New York City has already demonstrated that the energy saving potential of green roofs through evapotranspiration can significantly help to offset the water resources used to generate the electricity for mechanical cooling.
Through the daily dew and evaporation cycle, plants on vertical and horizontal surfaces are able to cool their surroundings. In the process of evapotranspiration, plants use heat energy from the environs when evaporating water, a process that reduces the urban heat island effect.
Green roofs can also cool intake air from air conditioning units, which results in further energy savings for organizations. In other words, energy equals water, and water equals energy—to varying degrees when it comes to green roofs and walls.
In many organizations, expert committees will apply integrated design and management principles and technologies to the issues of water shortage and urban greening. They will have to struggle with the fact that one size fits all solutions simply don’t work when it comes to water, and fms with a level of green roof knowledge will be valuable in finding sustainable solutions.
GRP Education Offerings
Successful green roofs require a combination of knowledge and expertise in the so-called “black arts” and “green arts.” The black arts focus on critical, non-living elements of a green roof assembly, such as waterproofing, structural engineering, and project management. The green arts deal with living architectural components, such as water management, growing media, plants, and maintenance.
Specialized training is valuable to any professional who wishes to understand the multidisciplinary field of green roof design, installation, and maintenance. Over the past seven years, GRHC has developed the Green Roof Professional (GRP) accreditation.
Until recently, few industry professionals possessed the knowledge and expertise that encompass all of these disciplines. Now there are more than 325 GRPs accredited in North America. Continuing education is vital to keeping up to speed with the evolving frontier of green roofs.
The GRP accreditation is supported by four professional development courses offered in different locations throughout North America. GRHC training was recently approved for continuing education units by the U.S. Green Building Council and is part of the American Institute of Architects continuing education requirements (as well as other regional professional associations).
Additionally, GRHC has developed a professional course on integrated water management principles and technologies in close partnership with the American Society of Irrigation Consultants.
GRHC will soon introduce its first course focusing specifically on maintenance, and fms will be the prime audience. The course will be a key component of the continuing education requirements of the GRP program.
Fms may benefit from the professional training that supports GRP accreditation by learning green roof skills alongside professionals from fields such as civil and structural engineering, architecture, horticulture, roofing, waterproofing, and landscape architecture. As green roofs become an important part in the future of sustainable building development, fms will continue to be one of the caretakers for these structures for many years to come.
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