Greenroofs

Ricardo Sá

Director of Sustainability

Edifícios Saudáveis Consultores (503 910 767)

LEEDuser Basic Member

79 thumbs up

November 29, 2018

Hi,

We are using the "Small Storm Hydrology Method" to calculate runoff volume and using the Rv based on impervious area. The questions are:

1) How shall a greenroof be accounted for in Rv Calculation?

2) Can we consider greenroof area as pervious area and therefore exclude it from the % of impervious area?

Thanks in advance,

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David Posada

Integrated Design & LEED Specialist

SERA Architects

LEEDuser Expert

1361 thumbs up

Thu, 11/29/2018 - 19:58

The green roof won't be considered pervious area if the run-off water doesn't infiltrate into the ground. Take a look at Joshua Radoff's blog post "The Reality of Rainwater in LEED v4" on the LEEDUser blog for a helpful explanation.

Michael DeVuono

Regional Stormwater Leader

Arcadis North America

LEEDuser Expert

144 thumbs up

Thu, 12/06/2018 - 14:11

A more beneficial approach for this is to model the site using the SCS methodology, and using a CN of lawn for the roof as opposed to a CN for impervious. The model will still predict some runoff, but not as much as a roof.

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