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,
David Posada
Integrated Design & LEED SpecialistSERA Architects
LEEDuser Expert
1976 thumbs up
November 29, 2018 - 2:58 pm
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 LeaderArcadis North America
LEEDuser Expert
186 thumbs up
December 6, 2018 - 9:11 am
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.