I am working on a small 2700sf visitor center project with an accessible green groof. The "system" covers 100% of the roof, but we have 2x2 pavers creating walking paths on the roof that account for approximately 730sf of the roof area. The pavers are laid directly over compacted growing media and spaced to allow vegetation to grow between. I can't find any language in the reference guide specifically stating that the green roof system has to be 100% vegetative, only that the system cover 100% of the roof to achieve exemplary performance. Will this installation meet the criteria for exemplary performance, or are the walking paths working against us?
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Mara Baum
Partner, Architecture & SustainabilityDIALOG
674 thumbs up
September 15, 2010 - 11:59 am
It's not reasonable from a maintenance standpoint to have literally a 100% green roof; it's not good for the plants to be walking on them. The exemplary performance requirement says "vegetated roof system" -- I would consider a vegetated roof system to also potentially include a limited amount of non-vegetated material. The system you describe would provide most of the stormwater benefits of a vegetated roof. If your pavers meet the SRI requirements, that would also provide most of the heat island benefits.
I haven't pursued this exemplary performance point myself, so others may have better insight.