COMPARATIVE EMBODIED ENERGY ANALYSIS TO ASSESS GREEN ROOF SUSTAIN ABILITY

摘要

Ironically, while we struggle to consistently value ecosystem goods and services within our current economic metrics, green engineering initiatives harness these same goods and services for sustainable but often quantifiably unknown benefits. New ecologically engineered living ecosystems, such as planted roofs and raingardens, have become a common strategy to earn green building certification through the United States Green Building Council's Leadership in Energy and Environmental Design (LEED) program. LEED promotes integration of these living systems into the built environment because they presumably increase environmental sustainability by reducing energy consumption, mitigating greenhouse gas emissions, reducing storm flows, improving water quality, conserving natural resources, and providing wildlife habitats. Although the economic costs for such projects are easily calculated, the environmental impact (or cost) of constructing these technologies is not readily apparent. To begin addressing this concern, we conducted a comparative embodied energy analysis (for this study we use emergy analysis) of two green engineered roofs (planted and cool/reflective) and a traditional modified bituman roof. We show the energy embodied in highly processed materials such as engineered soils can greatly impact a product's total sustainability despite its operational sustainability. We provide insight into the challenges of quantifying the level of "greenness" or sustainability of different sustainable or green engineered technologies. The results of our data collection and analysis for each roof are compared and contrasted from a practical perspective, considering the green roof industry's short term needs and subsequent long term viability.