In 2005, Temple University Ambler students, faculty, and staff, representatives from PECO Energy, state and federal officials gathered together to usher in the next phase of the University’s continued research into green roof technology.
So what is a green roof anyway?
It’s not just a color choice, a pleasant change from the typical black or gray shingling adorning the average household.
Green roofs are a choice, however, an environmental alternative to a traditional roof system.
Green roofs are alive; a living biological community of plants and microorganisms growing in a lightweight medium that provide an opportunity to revitalize urban landscapes ecologically, economically, and socially.
There are a few things you should know about green roofs and Temple’s continued cutting edge research into this technology:
Modern green roof technology was pioneered in Germany more than 30 years ago and has become a staple of design in many European countries — 12 percent of all flat roofs in Germany are green roofs. In the past few years, interest into green roof technology has begun to take root in the United States.
Nearly 50 percent of the world’s population and more than 220 million Americans live in densely developed urban environments.
This transformation of the Earth’s surface and termination of its biological processes has resulted in a deteriorating air quality, degraded water, and devastating urban “heat islands” — traditional roofs generate intense reflective heat. In warm climates, when air temperatures can reach 95°F or higher during the summer, roof surface temperatures can reach 175°F. An increase in the outside air temperature over roof surfaces contributes to and accelerates the chemical reaction that creates low atmospheric ozone, a primary component of smog.
By their nature, green roofs mimic the natural processes that buildings replace. The plant system has a positive impact on air, noise, and water pollution — atmospheric pollutants carried in rainwater are filtered through the plants and microorganisms, effectively serving as a bio-filter for improving water quality.
Green roofs provide extra insulation, helping to conserve energy in the winter and in the summer when the green roof substantially decreases roof temperatures, making it easier to cool the structure — temperature differentials between green roofs and non-greened roofs can be over 20°F on the roof surface.
Green roofs contribute to better stormwater management by trapping more water on the roof during a storm event and decreasing the speed with which stormwater makes its way into the ground systems — an important aspect of the technology, considering the attention focused on flood mitigation in the wake of an intense hurricane season.
Green roofs potentially increase the local biodiversity by providing habitat areas previously unavailable for animal life, particularly for nesting birds.
There are a few significant examples of green roof technology in use in the United States, including Atlanta City Hall; the Seattle Justice Center; the Ford Motor Company’s Rouge River Plant in Dearborn, Michigan; Chicago City Hall; Rockefeller Center in New York; the Fencing Academy of Philadelphia, and now the PECO Green Roof Garden at Temple University Ambler.
At the 2002 Philadelphia Flower Show, Temple University Ambler Landscape Architecture and Horticulture students provided the inspiration for the current green roof research taking place at the Ambler campus, bringing home a Best in Show Award in the Academic Educational category for a comprehensive green roof technology exhibit.
Three years later, Temple University Ambler remains at the forefront of green roof technology research, this week unveiling a working green roof atop the new Intercollegiate Athletics Field House, built with the assistance of a $50,000 grant from PECO, an Exelon Company.
A typical green roof may consist of several layers, from top to bottom: sedum plants, which trap dust, absorb carbon dioxide, release oxygen, and create habitat; vegetation blanket, a semi-organic material containing shale, sand, peat, compost, and dolomite; fleece, a felt-like absorbent mat of mineral wool that holds water; a drainage layer; and a root-resistant membrane, which protects the underlying roof from water and root damage.
There are two types of green roof systems currently being created in European and American cities. Intensive green roof systems utilize planting media depths greater than one foot that can support small trees and shrubs. Extensive green roof systems generally have planting media depths of less than one foot that support low-growing plants with a shallow root base. The PECO Green Roof is of the extensive variety, supporting colonies of carefully selected plants, all native to the region, in approximately six inches of a lightweight medium (shale mix). Extensive green roofs have much broader potential for replication on buildings in the United States.
The plants that make up Ambler’s PECO Green Roof Garden are made up of several species, most notably many types of sedums — a drought and humidity tolerant succulent plant, typically with thick, waxy leaves — and della spermum, another succulent that often goes by the name “freeway daisies” or “ice plants” for their hardiness and need for little maintenance.
Temple University Department of Landscape Architecture and Horticulture faculty are continuing detailed research to determine the plants that would best serve in a green roof structure in the northeastern United States, based on ease of propagation, rates of establishment, nutrient requirements, drought resistance, heat and cold tolerance, species competition, weed exclusion, and long term survival in this climate.
The potential impact of green roof technology on storm water management will be evaluated by measuring the volume of water held by the green roof system during storm events. Evaluation of the green roof runoff will include measurements of nitrates, phosphates, pollutants, and other water quality measurements.
The PECO Green Roof and related research is also providing students in the Landscape Architecture and Horticulture programs with real world, hands-on experience, a cornerstone of both programs. The green roof garden is a living laboratory — one of the many teaching gardens of the Amble Arboretum of Temple University — to instruct and inspire students and the public.