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The economics of land development sometimes dictate constructing structures and spaces that are unnatural or "anti-nature" because 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.   According to Oak Ridge 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).

Possible 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.

The 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. Vegetated 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).

Temperature fluctuations are modified with a vegetated cover.

Courtesy and Copyright Roofscapes, Inc.

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.

Temperature differences between ambient, roof membrane, and 4" and 8"deep  modules.

Courtesy and Copyright GreenGrid.

Overall 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 usage.

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).

Acoustic 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).

When 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. 

Most of the greenroofing companies utilize at least some recycled materials in their various product components. 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.

Being green can increase brand value and company profits!  Additional financial benefits through goodwill may be harder to quantify, but still have the potential for value.  Any 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 settings.

(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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