Introduction
Leadership in Energy and Environmental Design (LEED) refers to a rating system created by the United States Building Council (USGBC) to provide certification to green buildings. The certification enhances human and environmental health in five key areas. On the other hand, a rooftop garden is an artificial garden created on the top of a building for aesthetic purposes, food production, temperature control, and architectural enhancement. Rooftop gardens have become more popular because of increased demand for green buildings, resource efficiency, and high quality of indoor air. LEED enhances sustainability in urban development and encourages innovation. It awards points that lead to certification. Assessments for the awarding of LEED points focus on nine major areas that include energy, location, regional priority, education and awareness, indoor environment quality, sustainable sites, design innovation, and utilization of materials and resources.
The Origin of Rooftop Gardens
The history of rooftop gardens dates back to ancient civilizations. The famous Hanging Gardens of Babylon are examples of the earliest examples of rooftop gardens recorded in history (Tsarouhas, 2014). The ancient ziggurats of Mesopotamia were the first known examples of roof gardens. The ziggurats were massive stone structures that provided access to various building tiers. The structures did not have interior rooms, and so, trees and flowers were planted on terraces of the ziggurats and provided relaxing places to shelter from the scorching sun. The Villa of the Mysteries is an example of a roof garden during ancient Roman times (Tsarouhas, 2014).
It was comprised of elevated terraces on which plants were grown. The medieval Egyptian city of Fustat also had several roof gardens. They are usually described as a series of tiered gardens that contained trees, vines, and shrubs, and are the best example of roof gardens from ancient civilization (Tsarouhas, 2014). Historians argue that the Hanging Gardens were created by King Nebuchadnezzar as a gift to his wife Amytis. The design included a series of arcades that supported the weight of the gardens and an elaborate irrigation system that pumped water from the Euphrates (Tsarouhas, 2014). Several species of plants and animals were found on the ancient structure. Other roof gardens were located in Palazzo Piccolomini, Italy, and Norwegian sod roofs.
Rooftop Gardens and the Award of LEED Credits
The Green Building Council’s LEED system awards credit to developers based on their level of performance in certain areas. All rooftop gardens are unique and earn credits in different ways. However, the procedure of awarding credits is the same. On sustainable sites, developers earn credits on-site development (protection and restoration of habitat and maximization of space), stormwater design, and heat island effect (Kubba, 2012). Regarding water efficiency, LEED credits are awarded for water-efficient landscaping. Energy and optimization credits are awarded for minimum energy performance and optimization (Nichols, 2017). Credits for materials and resources are awarded for material reuse and recycled content. A rooftop garden that has been installed on more than half of the rooftop surface earns 2 mandatory LEED points that contributed toward full certification.
Benefits of LEED
LEED certification enhances resource efficiency, energy conservation, and the productivity of communities. Other merits that are attributed to LEED accreditation include high return on investment, tax incentives, environmental conservation, and increased marketability of developments (Kubba, 2012). LEED promotes healthy and sustainable communities (Nichols, 2017). Green homes have become a trend in the construction company and many organizations’ main concern is to attain LEED certification. Surveys have shown that this certification boosts the value of buildings and their profitability even during harsh economic times (Kubba, 2012). For construction companies, LEED accreditation increases their credibility. On the other hand, it saves buyers money and provides an ethical system for enhancing sustainability in the construction industry (Nichols, 2017). In the international construction market, the demand for sustainable building options is on the rise. Green construction has become an industry standard that aims to meet that demand.
Impact on Facilities and the Environment
Rooftop gardens provide shade, improve energy efficiency, cool the air through evapotranspiration, and reduce the temperatures of roof surfaces. Other benefits include reduced air pollution and greenhouse emissions, improved human health and comfort, enhanced stormwater management, improved life quality, and enhanced water quality (Tsarouhas, 2014). These benefits are some of the reasons why rooftop gardens have become a trending topic in the construction industry. Many urban developers are putting up buildings in line with the requirements of LEED certification.
Impact on Facilities
Rooftop gardens reduce energy use and improve human health and comfort by lowering temperatures inside buildings. They regulate the amount of heat that infiltrates buildings through the roofs, and as a result, enhance human comfort (Kubba, 2012). Moreover, they lower the amount of energy used for cooling during the summer, and as a result, leads to significant cost savings. Research has shown that covering the outer surface of a building is more efficient for temperature regulation than internal insulation. Roof gardens have extra layers that serve as heat insulators. In that regard, the layers reduce the amount of heat entering or exiting the building. This is beneficial, especially during winter and summer seasons. During the summer season, rooftop gardens protect buildings from direct solar heat that increases the internal temperatures that create discomfort (Kubba, 2012). During the winter season, rooftop gardens provide additional roof insulation that minimizes heat loss, thus maintain optimal temperatures inside buildings. In that regard, it lowers the energy used for heating. The leaves of plants on roof gardens trap dust particles and lower ambient temperatures through the process of evapotranspiration.
Roof gardens also improve the efficiency of mechanical equipment. The air on top of buildings with gardens is cooler than that on buildings without gardens. Therefore, mechanical machines perform better. Heat, Ventilation, and air conditioning (HVAC) equipment perform optimally by cooling outside air to the desired temperature. Roof gardens enhance the process of cooling, and therefore, conserve energy and make the HVAC equipment run smoothly. In that regard, low temperatures on rooftops enhance the efficiency of mechanical equipment and lower greenhouse emissions.
Rooftop gardens also increase the longevity of roofs by protecting them from direct ultraviolet radiation from sunlight. Moreover, it protects roofs from extreme temperatures, especially during the summer. Roof gardens lower maintenance requirements because roofing materials are rarely replaced or renewed. Rooftop gardens that are well maintained extend roof life and save the costs of replacement. Roof gardens also impact buildings by providing amenities that enhance the comfort of occupants. Accessible gardens in urban buildings increase green space, provide aesthetic views, and create recreation sites. Some gardens incorporate urban agriculture, which supplies food that can be used by the occupants of buildings.
Environmental Impact
Rooftop gardens improve the environment by enhancing stormwater management and lowering greenhouse emissions. In developed countries, approximately 30 percent of carbon dioxide emissions originate from the processes of heating and cooling buildings. Rooftop gardens lower greenhouse emissions by conserving energy. As mentioned earlier, the insulation provided during winter lowers the energy used for heating and the insulation provided during summer lowers the amount of energy used for cooling. HVAC machines mainly use fossil fuels to run, and as a result, release greenhouse gases into the atmosphere (Kubba, 2012). LEED-certified buildings address the problem of greenhouse emissions because they have 34 percent lower carbon dioxide emissions than non-certified buildings. Also, the consumption of energy is 25 percent lower. The process of photosynthesis lowers the amount of carbon dioxide in the atmosphere. Plants manufacture energy using carbon dioxide as one of the key components and release oxygen as a byproduct.
During seasons of heavy rains, roof gardens protect stormwater infrastructure from damage by retaining rainwater. The water is absorbed by plants and later returned to the atmosphere through the processes of evaporation and transpiration. It also conserves fish habitats because the stormwater that flows from roof gardens is cleaner and contains fewer toxic substances than water from conventional roofs. During heavy rains, too much stormwater causes sewer damages and overflows. This causes the discharge of sewage waste into water bodies, thus impacting aquatic habitats negatively. Roof gardens address this problem by retaining water in the growing medium and vegetation.
This retention lowers the amount of water that flows into the ecosystem. A study conducted by researchers at the Center for Green Roof Research at the University of Pennsylvania revealed that rooftop gardens retained approximately 80 percent of rainwater. On the contrary, conventional rooftops retained only 24 percent of the rainwater. The water-retention capacity of roof gardens increases as vegetation grows and root systems expand. In certain cities, buildings with rooftop gardens pay relatively low stormwater management fees because most of it is retained by plants. Another benefit of roof gardens is the filtration of water. The high amounts of carbon dioxide and greenhouse gases in the atmosphere cause acid rain that has adverse effects on plants, aquatic animals, and infrastructure.
The Success of Rooftop Gardens
Rooftop gardens are highly successful primarily because of their economic and environmental benefits and have become a trend in the building and construction industry. The trend has been promoted by government agencies and adopted by developers of hotels, corporate buildings, and housing estates. Increasing calls for sustainable living and environmental conservation have promoted the development of rooftop gardens. Besides, the trend has been augmented by the need to lower the carbon footprints of companies. Rooftop gardens have become key components of urban planning because they increase the marketability and the capital value of buildings. LEED certification is another reason for the success of rooftop gardens. Certification is done through the awarding of credits and occurs at four levels.
Certified buildings accrue between 40-49 credits while silver buildings accrue between 50-59 credits (Nichols, 2017). Buildings certified at the gold level have between 60-79 credits, and buildings with more than 80 credits are classified as platinum. In that regard, if any developer wants to be a leader in the construction industry, then LEED certification is a must because it promotes green building and enhances a company’s public image (Nichols, 2017). Companies that adhere to the requirements of LEED certification enjoy several incentives. For instance, according to the US Green Building Council, LEED-certified buildings have higher lease-up rates. Also, they sometimes qualify for tax rebates and exemption from stringent zoning restrictions (Nichols, 2017). Certified residential buildings sell faster and at higher prices than non-certified buildings. The US government offers a $2,000 tax credit for constructors who develop green homes, which also attract lower insurance premiums.
Conclusion
Rooftop gardens have become a beneficial trend in green construction. The protection of the environment is a major concern in the construction industry. LEED certification is a building rating system that allows companies and contractors to embrace green building and enhance the value of their developments. The certification process involves the allocation of credits based on a building’s adherence to certain design requirements. The credits are calculated and the building is placed in any of the four certification levels, namely, certified, silver, gold, or platinum.
Rooftop gardens contribute immensely to LEED certification because of the environmental value they offer. The lower greenhouse emissions, enhance the management of stormwater and reduce energy consumption in buildings. Moreover, they earn credits in several areas including sustainable sites, water efficiency, energy and optimization, and the utilization of material and resources. Rooftop gardens that cover more than half of the roof surface receive more than seven points that are necessary for LEED certification. These gardens earn LEED credits for maximizing open space, protecting or restoring habitat, effective stormwater design, water-efficient landscaping, and the optimization of energy performance.
References
Kubba, S. (2012). Handbook of green building design and construction: LEED, BREEAM, and green globes. New York, NY: Butterworth-Heinemann.
Nichols, M. R. (2017). Understanding the benefits of LEED certification. Web.
Tsarouhas, G. (2014). Green walls green roofs: Designing sustainable architecture. New York, NY: Image Publishing.