Green Roof Technologies
Without question, 2007 gave green roofs and green roof technology an
accepted place and a permanent and prominent role in the greening of American
cities and architecture. As to actual sales, the year was so significant that
one manufacturer of green roofing systems installed more vegetative roofs in
one month in 2007 than in all of 2006.
A big turning point in green roof acceptance occurred in 2001 when, with
great fanfare, Chicago installed one of the
largest green roofs in North America atop its
City Hall. Spurred on by the city’s enthusiastic mayor, who was eager to make
Chicago the greenest city in the United States, the rooftop garden was designed
to test different types of green roof systems and to determine their heating
and cooling benefits, success rates of native and nonnative vegetation, and
reductions in rainwater runoff.
Monitoring of the roof began in 2002, and the roof still serves as a
living laboratory to study green roof technology and its benefits. Results have
been encouraging. For instance, studies indicate that the temperature of the
existing roof below the green roof has been as much as 78 degrees cooler than
the temperature on the traditional black tar roof membrane that still exists on
half of the building. This has translated into lower energy costs, especially
in the heat of summer, to cool the half of the building with the green roof.
The Chicago
City Hall green roof was
a turning point for another reason as well. The green roof installed on the
building was a conventional built-in-place system, with workers placing soil
and planting vegetation directly on top of the building, similar to building a
garden. Several challenges were encountered with the installation atop the
nearly 100-year-old structure, resulting in the development of a new
technology, modular systems, that helped streamline the installation process
and make it more cost-effective. With this system, the soil and vegetation are
pre-planted in recycled plastic modules off-site, and then the modules are
installed directly atop the roof. The system allows for more flexibility and
for faster installation, helping to reduce labor costs.
Another advancement in green roof technology that has driven its
acceptance addresses the problem of the brutal rooftop environment. In the past
10 years, we have seen the development of engineered soil — soil that is
specially prepared with the proper macro- and micronutrients, air spacing, and
irrigation capabilities — to help the vegetation on a green roof not only
survive but also thrive. Additionally, green roof engineers have been better
able to pinpoint specific vegetation native to individual climates — such as
sedums, delosperma, sempervivum, and grasses — that can also thrive in these
brutal environments.
With positive early environmental and energy results, new technologies
in place to help lower installation costs as well as speed up the process, and
engineered soil and proper plant selection, it is estimated that nearly 90
percent of the total green roof square footage installed in the United States
has occurred from 2004 to 2006. Today, the cities with the most green roofs in
North America are Chicago; Washington,
DC; and Toronto,
Canada.
Another turning point leading to further acceptance of and interest in
green roofs has been the result of more and more studies from a variety of
independent organizations promoting green roofs’ virtues. For instance:
- Research from around the world
indicates that green roofs reduce annual storm-water runoff from roofs by at
least 50 percent, and often by 60 to 70 percent. Moreover, the rate of release
following heavy rainfall is slowed, reducing the problems associated with storm
surges on local water-treatment facilities.
- Green
roofs have helped reduce the need for air conditioning in many facilities in
the summer and therefore reduced CO2 emissions.
- Green
roofs can contribute to biodiversity and address local biodiversity action
plans.
- Green
roofs help mitigate urban heat island effect, keeping these areas cooler during
the heat of summer.
- The
life of an existing roof is at least doubled with the addition of a green roof,
thereby reducing costs for roof
replacement and repair.
There are many more reasons why green roofs have finally grown in
popularity. What we see happening now and expect to see in the future is even
greater acceptance of this technology. With some architects, developers, and
campus planners, installing a green roof atop a new facility is already
considered mandatory. Green roofs are seen as one way of minimizing a
facility’s footprint and impact on the environment as well as a way to give
back to the environment.
Jim Lindell is national
marketing manager for GreenGrid Green Roofs, a leading manufacturer of Green
Roof systems. GreenGrid is a business of Weston Solutions, Inc. Lindell can be
reached at
[email protected].