A Difference of Opinion
There is currently a significant controversy in the roofing industry regarding the proper design methods for resisting wind uplift for vegetative roof systems. It seems that the various organizations looking at this matter cannot come up with a standard that everyone can agree is technically correct and sound. Hopefully, continued discussions will end with an agreement but right now there is a wide difference of opinion regarding the approach and even the appropriate conclusions that can be made from various testing programs and data related to this issue.
If you have or are considering the installation of a vegetative roof, get good technical guidance and advise!