Allegheny County’s Monitored Green Roof

Foreground: intensive green roof and microcosm trials image: John K. Buck, Civil & Environmental Consultants, Inc.
Foreground: intensive green roof and microcosm trials
image: John K. Buck, Civil & Environmental Consultants, Inc.

To serve as an educational model demonstrating the benefits of green roofs and the technology imbedded in green roofs, Allegheny County, Pennsylvania decided to install a green roof exhibiting four types of green roof technologies:

  1. Intensive – 8-12 inches of lightweight engineered growing medium with shrubs and plants requiring that rooting depth.
  2. Semi-intensive – 6 inches of lightweight engineered growing medium with the ability to grow plants and shrubs with that depth.
  3. Roll out mat – a pre-grown sedum mat set on 4 inches of lightweight engineered growing medium, providing instant coverage.
  4. Tray system – pre-grown sedum established in lightweight engineered growing medium trays.

By exhibiting these four green roof technologies, it is noted that the substantial additional weight of the intensive and semi-intensive systems requires close examination of the structural integrity of a roof, whereas the mat and tray systems allow green roof application on roofs with less significant weight restrictions. In addition to the visual display, monitoring systems were installed to prove the benefits of green roofs. The performance of this green roof is amazing and noteworthy to share in the scheme of green technology.

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