Lightweight Green Roof Systems

EPA Grant Number: SU834730
Title: Lightweight Green Roof Systems
Investigators: Hsuan, Grace , Zakutny, Matthew J , Hoffman, Patrick T , DiGiovanni, Kimberly , Magee, Michael , Mickute, Monika , Nakao, Yuka
Current Investigators: Mickute, Monika , Zakutny, Matthew J , Malawski, Kevin , Magee, Michael , Spatari, Sabrina
Institution: Drexel University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $9,952
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text |  Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Built Environment , P3 Challenge Area - Water , P3 Awards , Sustainability


Applying a Lightweight Green Roof System to a building can achieve in managing storm water runoff, decreasing heat gain, yielding energy savings, and mitigating the heat island effect. Currently, Most green roof systems are considerably heavy and require structural reinforcement of an existing structure. The soil in the vegetative roof system saturated with rainwater accounts for the majority of the weight. Replacing soil with a natural and/ or synthetic light-weight planting medium enriched with nutrients has the potential to eliminate the need to reinforce existing buildings and still provide the benefits of vegetated roof. This project will demonstrate that the introduction of a combination of light weight materials can grow and sustain roof vegetation while reducing the heat island effect and harmful water runoff. The team will use analytical methods to evaluate growth medium chemistry, a rain simulation apparatus to evaluate prototype water retention, accelerated weathering and tensile tests to qualify materials, and artificial metal halide lighting to grow prototypes of green roof systems. The team will integrate green roof concepts into an outreach program run by the Drexel Smart House organization which gives public educational workshops on improving residential building envelopes in the West Philadelphia community. Researchers will also advise the Philadelphia Water Department on residential runoff reduction strategies.


Develop and test a light-weight modular green roof system for retrofitting existing buildings, eliminating the need for structural reinforcement to accommodate the system. The resultant prototypes will retain storm water, decrease heat gain, insulate the underlying roof, mitigate carbon from the atmosphere, and save heating and cooling energy.


A light-weight green roof will consist of the synthetic base planting medium with characteristic high water absorption and low unit weight. It will be pre-assembled units of encapsulated growth medium and vegetation. The system will be tested for moisture and nutrient retention, its ability to discharge excess water after it had reached its full saturation point, vegetation growth rates, durability, weathering and overall performance.

Expected Results:

The team expects to reach the appropriate combination of materials to construct the planting module for a light-weight green roof system. Prototypes will be assembled using commercially available, recyclable materials. This research will be integrated into a variety of educational programs, including undergraduate design projects and public educational workshops.

Supplemental Keywords:

building envelope, insulation, water retention, Carbon reduction, carbon sequestration, heat island effect, sustainable water management, storm water management, green roof, energy conservation,

Progress and Final Reports:

  • Final Report
  • P3 Phase II:

    Lightweight Green Roof Water Retention System