By Dennis B. Carmichael, FASLA
Principal, EDAW, Inc.
dennis.carmichael@edaw.com
Landscape architects are a valuable professional to have on any development or building project seeking LEED certification. In fact, up to 18 LEED points are centered around the landscape. Most people immediately think of heat island reduction and water efficient landscaping, but those areas are a small part of a larger potential contribution of the landscape.
First and foremost, landscape architects can help with site selection. Their training in natural and cultural systems gives them the knowledge to select sites, or areas within sites, which minimize impact to soils, hydrology, vegetation, and wildlife habitat. This is a hugely valuable decision, which can contribute to the sustainability of a given development or building. Thus, landscape architects can guide strategic decisions among sites (brownfield versus greenfield) or within sites to achieve development in harmony with natural systems. Tactically, they can also work at the site scale to minimize site disturbance, preserving and enhancing the highest quality resources while developing upon the least sensitive.
This approach of designing with nature is not only environmentally sound, but can save money in the development process. Landscape areas preserved within a development project save money in three ways: eliminate the cost of clearing, eliminate the cost of re-planting, and reduce the cost of landscape maintenance. While much has been written about the cost of going green as a premium, in some areas of the landscape, it is actually less expensive to practice sustainability, through the selective preservation of natural areas.
Another area of master planning that landscape architects have a strong contribution is alternative transportation, namely bicycle and pedestrian ways. By providing safe, convenient, and comfortable sidewalks and bicycle paths in a comprehensive network, communities can reduce automobile trips. While LEED does not recognize pedestrian convenience in it New Construction tool, it is a crucial aspect of its Neighborhood Development tool. And both tools recognize the value of bicycle paths, storage areas, and employee wash rooms as a potential point. It is worth noting that these systems not only reduce vehicle emissions, improving air quality, but they also promote good health, reducing the risk of obesity, diabetes, and heart disease.
Stormwater management is often seen as the purview of civil engineers, and they perform a valuable function in designing systems for both quantity and quality of stormwater runoff. Increasingly, though, natural systems are being introduced as stormwater solutions and landscape architects are well positioned to assist in the design of these facilities. These natural solutions, including rain gardens, bioswales, and wet ponds, have the added benefit of creating wildlife habitat, as well as a more beautiful insertion into a landscape setting. What is also noteworthy of these natural solutions is that they promote infiltration of stormwater at the source, rather than piping and storing it in regional facilities. In many instances, the costs associated with a system of rain gardens, bioswales, and constructed wetlands is less expensive than the cost of a traditional engineered system of drains, pipes, and sand filters. Natural systems may utilize more land than engineered systems and therefore land costs must be factored into any cost/benefit analysis. One way to reduce those land areas is the use of porous paving to minimize stormwater runoff amounts and therefore reduce storage requirements.
The heat island effect is well documented as a contributor to poor air quality and global warming. It is also well documented that shade trees have a tremendous contribution to cooling the ground and the air. What is less known, but equally valuable, is the function of trees and shrubs as storage for carbon dioxide. Plants consume carbon dioxide and release oxygen, a double benefit for humans. As we strive to reduce our carbon emissions in buildings, we should also be increasing carbon sequestering through increased tree planting, especially in urban areas.
Another way to reduce heat island effect is by creating a green roof. Whether a thin veneer of soil and planting (extensive green roof) or a more robust garden meant for human occupation (intensive green roof), green roofs soak up stormwater, reduce roof temperature, and insulate buildings. The insulting property of a green roof offers terrific economic benefits to a facility, as it reduces annual heating and cooling costs and also increases the life of the roof membrane. While the premium for an extensive green roof can be $15 – $25 per square foot over the base cost of a roof membrane, it will pay for itself over a 10-20 year period through energy savings and elimination of one roof replacement cycle every 20 years. Facility managers should give serious consideration to green roofs as a cost-saving strategy over the life of a building.
Besides plantings, landscapes can help reduce heat island effect through the use of pavements that are light in color and porous. Light-colored walks, patios, and parking areas reflect rather than absorb heat, providing measurable reduction in heat gain. Porous pavings allow for infiltration of water, which also serves to cool a given field of paving.
All landscapes require water to flourish, and the best way to manage landscapes sustainability is to minimize the use of potable water for that purpose, preserving this most precious of resources for human consumption. Plants should be selected that are native to their region or to the available water regime. In this manner, plants can survive on available rainfall. If irrigation is required, then areas should be carefully zoned to provide appropriate water amounts in accordance with landscape types. Drip irrigation should also be considered, as it does not allow evaporation to waster water. Finally, grey water should be used for irrigation, stored in either cisterns or retention ponds, wherever possible to minimize use of potable water. Facility managers should create a water budget for a given site, so that there is a comprehensive understanding of supply and consumption required annually. In this manner, decisions can be made to balance supply and demand, essentially the definition of sustainability.
Landscape is not traditionally considered as part of an energy management plan for buildings, but there are two areas in particular where landscape can reduce energy costs. As mentioned above, green roofs are an excellent insulator of buildings and provide energy savings. Tree plantings that shade window walls are also an effective passive solar control. Especially in temperate climates, deciduous trees on the south, west, and east window walls provide for cooling shade in summer, while allowing low winter sun to provide passive heating, yielding year round energy savings.
Recycled materials are increasingly being used in buildings, but can also be considered in the landscape as a means to reduce the waste stream. Decking members made from recycled plastic are commonly used for boardwalks, decks, and marinas. Playground safety surface made from recycled rubber tires are available in a variety of colors and forms. Decorative pavers incorporating crushed recycled glass as an aggregate are now being manufactured. Each of these products offers safety, durability, and beauty, while reducing demand on landfills.
All of the above strategies in the design of landscapes can contribute to LEED certification points. While this recognition is valuable for a given building or site, of equal value is the cost savings associated with sustainable landscapes over the life of the project. Good ecology leads to good economy over time and landscape architects can make a valuable contribution to that end for buildings, sites, and facilities.
Dennis Carmichael, FASLA, is a landscape architect and principal with EDAW, Inc., in Alexandria, Virginia. He is the immediate past president of the American Society of Landscape Architects and is a member of its distinguished Council of Fellows. He may be contacted by e-mail at: dennis.carmichael@edaw.com.