The economics of land development
sometimes dictate constructing structures and spaces that are unnatural or
they are cheaper to build. We should reverse this philosophy and invest in
the future of our environment by initially expending more financial capital to
produce buildings that will reap biological and financial savings later.
The initial extra short-term capital
costs of greenroof construction can be offset through long-term energy and
maintenance savings. The economic
benefits represent real reasons for local municipalities, developers and private
residence owners to consider opting for a greenroof although first costs may be
higher. And in fact, the U.S. Green Building Council and others say that
new advances in green design have shown that a green building doesn't
necessarily have to cost any more than a conventional one.
Quality control in terms
of diligent installation and maintenance procedures are essential for all roofs.
National Laboratory (ORNL), most roofing systems fail from leaks, and the
average roof needs to be replaced four times. In addition to replacement
cost savings and construction waste reduction, ORNL estimates that if low-slope
roofing systems could be kept dry, more than three-fourths of a quadrillion BTUs
of energy could be saved each year in the United States (Kennedy,
PlantServices.com, August 15, 2006).
impervious coverage restrictions may be reduced for developers who incorporate
greenroofs into their site plan.
Depending on local ordinances, greenroofs may be installed in lieu of
conventional stormwater practices. They can significantly reduce the size, or
even completely eliminate, the necessity for unsightly, space-wasting, and
expensive detention ponds or underground galleries (Roofscapes, Inc., 1998). Although hard to quantify, there is also potential for downstream stormwater
treatment savings. See Industry Support
for more info.
life of the underlying roof waterproofing membranes can be extended by using
greenroofs to shield the roof from the effects of ultraviolet radiation,
temperature extremes and mechanical damage.
areas heat up much less than exposed surfaces of asphalt or bitumen.
According to literature of Erisco-Bauder Limited of England, “During
the summer at high times of solar radiation, roof surface temperatures are much
higher than the air temperatures, up to 80 degrees C (176 degrees F).
On clear winter nights, when there are high levels of heat radiation
directed upwards, the temperature of roofs can drop below that of air and reach
–20 degrees C (-4 degrees F).” In
winter erosion damage and fracture of most roof surfaces by frost and ice can be
lessened or even eradicated (The London Ecology Unit, 1993).
Reduced stresses on
roofing materials typically double the service life, prolonging the practical
life by 20 years. Other estimates say a
greenroof can actually triple the life of its roof. Therefore, the
costs for rehabilitation or replacement of roofs can be delayed.
building energy costs can be reduced due to the greenroofs’ natural thermal
insulation properties – vegetated roofs reduce building heat-gain, so structures are cooler in summer and warmer in winter.
The urban “heat island” effect can also be greatly reduced since
vegetative roofs reduce ambient air temperatures.
Therefore, less electricity costs are expected from lower a/c and heat
According to an article from the
Environmental News Network, "a 3- to 7-degree temperature drop translates
to a 10% reduction in air conditioning requirements. For a one-story
structure with a green rooftop, cooling costs can be cut by 20 to 30%."
The Weston Design Consultants recently conducted an energy study for the city of
Chicago which estimated that it would be possible to save $100,000,000 in saved
energy annually with the greening of all of the city's rooftops. The
bottom line is that "Peak demand would be cut by 720 megawatts - the
equivalent energy consumption of several coal-fired generating stations or one
small nuclear power plant." (www.enn.com/news/enn-stories/2000/12/12302000/rooftops_40979.asp).
insulation properties also exist with greenroofs, and many have been placed near
airports yielding great results in noise reduction.
Due to the soft plant level of extensive greenroofs, sound insulation can be
reduced up to 8 dB (www.zinco.de/evorteile.htm).
According to Erisco Bauder Ltd. of England, “Noise protection can be as
much as 25% for the extensive roofs and more for the intensive alternative.” The
exact amount of noise reduction is hard to quantify and depends mostly on the
thickness of the soil substrate and additional factors, i.e., leakage from
skylights, but overall, up to a 50 decibel noise reduction
can be realized (McMarlin, May/June, 1996).
greenroofs are applied, previously wasted rooftop space is turned into usable space.
The high price of land
may inhibit creating green areas at ground levels, and property values could
rise as a result of utilizing the roof space. Extensive greenroofs
may simply beautify the building; with
intensive greenroofs, open space for human interaction, such as terraces or
plazas, is provided on an otherwise neglected area. In turn, value is added for
building occupants, clients and guests.
of the greenroofing companies utilize at least some recycled materials in their various
Disposal sites and landfills are thereby saved, and recycling just makes good economic sense.
A new market for greenroofs and
services could create jobs for many people. Green Roofs
For Healthy Cities makes a correct observation that states that the demand for greenroof installations would require
and therefore help create a business market for manufacturers and
suppliers of all the required physical components, i.e., all the greenroof
layers as well as specialized garden nurseries, in addition to the services of architecture, landscape and
ecological design and engineering
professionals, as well as a work force of laborers, and maintenance personnel.
green can increase brand value and company profits! Additional
financial benefits through goodwill may be harder to quantify, but still have the potential for
company or institution desiring to promote itself as being pro-environment would
greatly benefit from incorporating a greenroof into any sustainable design plan. Positive public relations and
goodwill can be created for businesses that use eco-friendly greenroofs.
Perhaps public anger towards traditional “unecological” industries
can be mitigated somewhat by the green architecture.
The uniqueness of the environmentally
forward-thinking owner who incorporates a greenroof could offer a competitive advantage to
that individual merchant or community development. Free advertising may result from increased public
interest in the newness of the concept. Recognition
could also be garnished from design awards or the active promotion of the environment.
Hopefully, future tax breaks for building greenroofs will establish
financial incentives for businesses and private individuals alike.
When coupled with
financial incentives from municipalities, savings attributable to the extended
service life of roofs, reduced energy consumption, and avoided costs associated
with compliance with local stormwater regulations greenroofs may generate a
positive return on investment. (Charlie Miller,
2009). Aside from being
unobtrusive, low maintenance, and reliable storm water management systems,
greenroofs can add natural beauty and aesthetic relief to a wide variety of
(Charlie Miller, 2009). "Stormwater
regulations differ widely among states and municipalities. Furthermore,
ordinances in metropolitan areas often are unrelated to regulations that may
apply in neighboring suburban areas. Typically, stormwater management
regulations in urban areas are more favorable toward green roofs and other best
management practices (BMPs). In many cities green roofs are recognized as an
option for satisfying stormwater requirements. Where compliance with the Clean
Water Act is decisive factor, some cities offer financial incentives (e.g, tax
credits, subsidies, relief from utility fees) for green roofs. (Charlie Miller,
2009). Greenroofing solutions extend the insulating
properties and life cycles of underlying membranes for reduced energy
consumption, exhibit low environmental impact, and increase building
sustainability (The Garland Company, 1999).
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