Growing Green
A green roof is good for the environment and good for your pocket book.
By Robert Bajarunas
It was once thought that weeds and twigs growing in your old leaking roof was a bad sign. Well, maybe that is still the case but controlled vegetation on the roof is becoming more of the norm. The growing of plants on a roof is intended to replace the vegetative footprint that was lost when the building was constructed, and they come in all shapes and sizes. From a simple bed of sedums, to a living outdoor space with shrubs and trees or possibly a vegetative wall, the designs and benefits are only limited to your imagination. This article will focus on different types of green roof solutions.
There are two ways of classifying green roof systems: “extensive” or “intensive” based on required maintenance. Intensive green systems consist of thick substrates, which support a wide assortment of plant types including shrubs, perennials, annuals and grasses. Due to the depth of the system — 8 to 36 inches — this specific type of system requires the structural ability to support the additional weight. In other words, it is intended to be an outdoor living space. Keep in mind, due to the nature of this growth, considerable maintenance is required such as watering, weeding, pruning, cutting and fertilization.
The other type of green roof system is extensive. Extensive roof systems have enjoyed the most popularity as of recently. Typically these systems range from 3 to 8 inches deep. This system is made up of lightweight layers that bear a drought-resistant ground cover type of vegetation. Because they are lightweight there are numerous possibilities when it comes to application choices. Extensive roof systems are tolerant of extreme weather such as wind, drought and temperature effects. Thus, there is little needed when it comes to maintenance, fertilization or irrigation.
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Extensive roof systems are tolerant of wind, drought and temperature effects. Thus, there is little needed when it comes to maintenance, fertilization or irrigation.
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Vegetative systems contribute greatly to savings on energy consumption. They supply a natural layer of insulation to the building, providing warmth in the winter and a cooler interior space in the summer. Installation of a green roof system helps alleviate damage caused by the common occurrence of expansion and contraction due to daily temperature swings from day to night. It will protect the roof membrane from ultraviolet radiation, extreme temperature fluctuations and physical damage such as punctures. Depending on the building location, design of structure and the material used in the construction of the waterproofing membrane and green system, the savings can be anywhere from 15% to 75%. This is because the plants absorb and temporarily retain the heat. Green roofs could even help alleviate global warming by reducing the urban-heat island effect. Heat islands are essentially where dark colored, impermeable surfaces absorb heat energy and radiate it back into the air. The result is an increase in temperature 2% to 10%, which affects energy use and may cause health problems because the quality of the air diminishes.
Another benefit is that growing media, vegetation and layers of trapped air in the system serve as great sound insulators. Vegetative roof systems have the ability to reduce indoor noise pollution as it relates to outside contributors by approximately 10 decibels. In addition, every major city has a growing problem with storm water, and until more permeable surfaces are created, our drainage systems will be constantly tested and risk flooding. Vegetative roofs collect and utilize storm water and discharge the same water moderately over an extended time period. For example, a 4-inch-thick extensive green roof will retain a half-gallon of water per square foot, or 60% of an average 2-inch rainfall.
Finally, green roofs aid in providing a more natural habitat for insects and birds, which typically have limited space in large cities. Studies have shown that green roofs as high as 20 stories attract butterflies, bees and birds. They could even support up to 40 different insect species as well as nesting bird species.
The green roof concept is becoming more prevalent and widespread throughout the U.S. The general public and elected officials see the positive impact and benefits gained from vegetated systems. In fact, green roof growers and roofing manufacturers are teaming up to offer complete system warranties. As it takes time to watch a plant reach maturity, so does the mindset of a nation to take a proactive approach to turn our cities into a verdant urban area.
Robert Bajarunas has over 12 years of experience in the roofing industry and is vice president/operations of R. Commercial Roofing Solutions, a Rabine Group Company. Headquartered in Chicago, R. Commercial Roofing Solutions provides consulting, maintenance and construction for all commercial roof types. For more information, call 888-ROOF131 or visit www.CommercialRoofPros.net. |
