By Peter Belisle
Published in the August 2008 issue of Today’s Facility Manager
(Photo Credit: Tecta America.)
Throughout the U.S., organizations are embracing and announcing environmental sustainability goals in the hopes of reducing costs, improving productivity, gaining a competitive advantage, and enhancing their images. Green roofs, already popular in parts of Europe, are catching on as an environmentally sustainable building practice in the U.S.
Among their many eco-friendly benefits are increasing insulation to help reduce energy requirements; lessening of the urban “heat island” effect; and cutting noise, carbon dioxide, and pollutants in the surrounding atmosphere. Green roofs can also contribute to credits toward the U.S. Green Building Council’s LEED¨ (USGBC) certification.
More importantly, however, green roofs are a visible way for companies to showcase their dedication to sustainable design by protecting the environment. Green roofs have also become a way to engage employees in a work based environmental cause through voluntary planning, development, planting, and maintenance of the garden.
Costs Of Installation
Despite their many benefits, green roofs can be expensive. Currently, the up front cost of an extensive green roof in the U.S. starts at about $8 per square foot, which includes materials, preparation work, and installation.
In comparison, the cost of a traditional built up roof starts at about $1.25, while cool roof membranes start at approximately $1.50 per square foot. In exchange for the expense, green roofs can last two to three times as long as a regular tar roof.
To help cover the high costs of green roof installation, many cities, including Chicago-where one of the first major extensive systems was installed atop City Hall-Philadelphia, Washington, DC, and New York now offer property tax cuts and other incentives to buildings with green roofs.
A Readiness Checklist
Some facility managers (fms) wonder if their buildings are actually ready to incorporate the green roof concept. The checklist that follows should assist in the evaluation process.
Condition: Will structural modifications need to be made to the existing roof to support the added weight? If so, are any roof modifications set for the near future? This planned maintenance program is an ideal time to ready a roof for greening.
Access: Is the rooftop easily accessible for development and maintenance?
Pitch: Is the rooftop generally flat, with no more than a 30û pitch?
Light: Does the rooftop get enough sun to keep the vegetation thriving? Is it in the shadows of larger buildings or trees?
Cost: Does the facility’s budget allow for spending between $8 and $12 per square foot to develop a green roof?
Labor: Will employees participate and help save labor costs?
Visibility: Is the rooftop visible for everyone to enjoy?
Use: Will the green roof be designed as an additional outdoor amenity space for occupants?
What Type Of Green Roof?
Once the roof has been proved to be structurally sound and plans are ready to move forward with a green roof initiative, the fm needs to determine which type of green roof to install.
There are two types of green roof systems: intensive and extensive.
Intensive roofs, often known as roof gardens, are designed to be used by occupants. They typically contain a wide variety of aesthetically pleasing plantings, much like a park. While intensive systems may be more appealing to the eye, they generally require much more regular maintenance, such as irrigation, feeding, and trimming.
Depending on the plantings, an intensive green roof can require much deeper soil, not only contributing just to cost but also to weight and stress to the building’s structural support. For that reason, intensive green roofs are most often found in shorter buildings or at low levels, such as over a parking garage or on an office tower protrusion like an entryway or lobby.
Extensive systems make use of extremely hardy, drought resistant perennial plant species that require little maintenance beyond infrequent weeding and fertilizing. From soil composition to choice of vegetation, extensive roofs are designed to survive the local climate with minimum care. The reduced staff time required to maintain an extensive green roof usually makes it the more economical choice for fms over the long term.
Another advantage of extensive roofs is that they normally require a soil depth of about 8″, less than half of how much intensive systems typically need. Consequently, they necessitate less additional structural support and are often more practical for sloping roofs or the tops of taller buildings.
While extensive roofs can also be attractive, they are especially valued for their contributions to environmental sustainability. Many green roofs are a hybrid of intensive and extensive systems, containing areas of both.
What Benefits Shall Be Reaped?
A properly designed and installed green roof of virtually any type can generate several eco-friendly and operational advantages including:
- Increased building energy efficiency;
- Reduction of “heat island” effect;
- Rainwater retention;
- Air quality improvement;
- Noise reduction;
- Extended service life;
- Aesthetics value; and
- Illustration to the company’s dedication to sustainability.
Environmental sustainability is not a passing fad, but a trend of the future for facility management, building design, and construction. Green roofs are a way for fms to generate positive community response while providing employees a more desirable workplace.
Belisle is president of Jones Lang LaSalle‘s Project and Development Services Group for the Americas.
Garden And Photovoltaic Roofing Systems: The Ease Of Going Green
By Riaz Hasan
As the green movement grows stronger every day, facility managers (fms) are doing their part to sustain the earth’s resources. With a growing number of green roofing system and accessory product offerings available, photovoltaic (PV) and garden rooftops stand out as two of the most efficient and innovative designs for commercial use.
PV systems consist of solar cells and panels that convert sunlight to electricity- saving energy costs for the entire building. PV systems also provide high energy efficiency, which helps reduce facility heating and cooling costs.
Two types of PV roofing systems are available to fms. The first, amorphous, is installed directly over the membrane and consists of solar cells placed over a stainless steel substrate then laid directly over the rooftop. The second option, crystalline, can be installed by penetrating the rooftop membrane or by putting the cells directly over the rooftop.
Because they are durable and lightweight, non-penetrating systems are essentially waterproof and very flexible, making them easy to apply to many flat rooftops. On the other hand, crystalline systems are 34% efficient compared to amorphous systems, which are only 9%.
Generally, PV systems demand minimal maintenance in the form of occasional panel cleanings. Additionally, the federal government and some states (such as California, Connecticut, New Jersey, and Hawaii) offer rebates to those companies that invest in solar energy. For example, a $6.54 million, one megawatt PV system installed in California cost only $820,000 after rebates.
Like many countries throughout the world, the U.S. is finally learning the value of garden roofing systems. These aesthetically pleasing rooftops improve energy efficiency, protect against damaging thermal fluctuations, and can even extend the life of the roof-all important factors for today’s conservation minded fms.
Aside from reduced energy costs, garden rooftops reduce thermal and ultraviolet (UV) degradation and decrease the urban “heat island” effect. The drainage systems of garden rooftops provide immediate evaporative cooling and purification and reduction of storm water runoff by as much as 75%, preventing heat and water damage.
In addition to intensive and extensive types mentioned in the accompanying article, garden rooftop systems are available in two forms: intensive (some of which may be modular pre-vegetation systems) and extensive, which are built in place. Modular pre-vegetation systems are installed pre-assembled and provide greater resistance to wind erosion while demanding less weeding and other maintenance. Some modular systems are made with 100% recycled plastic trays that are snapped together, ensuring the stability of the rooftop garden and cutting down on installation costs and time. Once installed, modular systems require minimal maintenance. Built in place systems are grown on-site, can take several months to mature, and require regular maintenance.
Garden rooftops protect the membrane and extend the life of the roofing system. Because of the roof’s ability to absorb sound and heat, rather than deflect it, outside noises and temperature effects are significantly reduced. Garden rooftops are not only eco-friendly and easy to install, but they improve the overall look of a building. Integrated paths, bushes, and even trees create a relaxing getaway right on the roof. Fms should consult with an architect or specifier to determine which garden roofing system is right for them.
Through PV and garden rooftops, fms can earn green building credits with the LEED Green Building rating system. PV and garden rooftops make it easy for fms to generate interest in their buildings without compromising the bottom line.
Hasan is an accessories product manager for Indianapolis, IN-based Firestone Building Products.
Photo credit: Firestone.