LEED-ING LANDSCAPE DESIGN™: GREENROOF DESIGN AND BENEFITS
More and more public entities, as well as private builders and developers, are designing buildings to earn the Leadership in Energy and Environmental Design (LEED) certification offered by the United States Green Building Council. Landscaping can provide a critical boost to architects, builders and developers hoping to demonstrate environmental LEEDership.
LEED credits, including those for landscaping, are earned in 5 simple categories. Categories include: Sustainable Sites, Energy and Atmosphere, Water Efficiency, Materials and Resources and Indoor Environmental Quality. An effectively designed greenroof, like the one at the Lofts & Cherokee Studios, can significantly bolster a building’s LEED rating by contributing in each of these categories.
The sustainable sites category includes management of storm water and heat island effect.
- Depending on the square footage, a roof can be one of the largest sources of storm water accumulation. In a typical year of rain in Southern California, a 1000sf roof can shed 7500 gallons of water into the storm run-off system. Multiply this by all of the cities homes and commercial buildings and we accumulate millions of gallons of storm water that is essentially “unmanaged”. Unmanaged water runs its course toward the ocean and carries known pollutants that adversely affect our air, ocean and wildlife.
- Greenroofs mitigate storm water flow, acting as a primary point of absorption for storm water. As it absorbs storm water, an effective greenroof not only collects water, it functions as a bio-filter. Depending on a roof design, a roof garden can absorb 4″ or more of rain prior to water entering a drainage system. Water not absorbed by plants and soil media, can potentially be captured and stored for other uses to eliminate runoff.
Heat Island Effect
- Heat Island Effect, the amplification of heat by hard surfaces in close proximity to one another, is especially problematic in urban areas where there are non-reflective and non-absorbent surfaces. Heat islands increase the need for air-conditioning and other energy-intensive and unhealthy strategies for mitigating the increase in temperatures.
- A greenroof can absorb sunshine, as well as amplified light and heat emanating from surrounding structures. If applied to all city roofs, greenroofs could actually lower temperatures in urban areas to be more consistent with their rural counterparts! In this way, greenroofs may be one of the more simple ways Americans can reduce overall energy consumption.
Energy and Atmosphere
Although greenroofs have been in use for centuries, the “green” movement has provided stunning data responsible for their come back in the 20th and 21st centuries. Current studies show that the protection from temperature fluctuations provided by greenroofs can result in energy cost savings up to 80 percent. With careful building performance monitoring energy savings can exceed standards set by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), one of the many standards and guides LEED applies to its Energy and Atmosphere credits.
In addition to reducing energy needs, the plant life on greenroofs can absorb greenhouse gasses. If the plant life includes edibles, the greenroof may also reduce reliance on food sources that require automobile travel for distribution or consumption, preventing atmospheric pollution at its source.
Despite studies that greenroofs do not aid in saving water, there can be synergies with improving water efficiency. The thousands of gallons that a greenroof can absorb can be captured, stored and reused for future irrigation to the greenroof or to other landscaped areas. A greenroof in Southern California does face particular challenges. Southern California greenroofs require very low water plants in order to minimize tapping into additional water resources.
Materials and Resources
There are multiple components that go into building a greenroof and all of them need to be sourced responsibly. Materials and resources applies to all LEED building practices, when it comes to installing a greenroof the largest material needs are soils and plants.
Soils typically need to be very light to qualify for roof weight thresholds. Much of the material that makes a soil media light is not environmentally friendly, for example perlite, a common additive in light soil mixes. Using organic materials is also not highly recommended since they decompose and change the level of a planting area and can cause clogging problems once decomposed. So finding a natural product, like coarse sand and keeping organic materials to less than 10 percent of the media will keep toxic materials out of your soil mixture.
Finding and buying these products locally and from companies that minimize their production and resale of other toxic products is ideal. Researching sources is important. Finding and utilizing plant material that is local, grown without chemicals in organic media is ideal.
Lastly selecting plants that are local or native to the region bolsters natural wildlife and will require less water and maintenance making the site more sustainable overall.
Indoor Air Quality
Amazingly enough, greenroofs do impact the last LEED category, indoor air quality. Indoor air quality improves when fresh, clean air is able to enter from the outside. If a greenroof is insulating and keeping indoor temperatures cooler, then forced air and HVAC systems can be reduced, increasing the use of windows that provide natural cooling. If there are fragrant plants on the roof, it’s possible a city dweller in a commercial building might benefit from some of those beautiful smells as well.
In short, whether you aim to earn a LEED rating or simply want to produce cost savings and beautiful, enjoyable space, greenroofs offer an extensive range of benefits. For More Information: