I just don't see it lasting too long. Theres been lots of "eco-phases" Plastic Bags, "Earth Ships", the list goes on... I just feel that some buildings will take advantage of having a lawn on the roof, but its adoption will be short lived. Why? while a green roof might not need to be replaced but once every 50 years, it does have to be maintained. So the whole Idea of moving into the city to avoid lawn care has just been thrown out the window. Is the cost of not replacing the roof as often save more money compared to just keeping roofs the way they are, and not having to pay for lawn care, even if theres an eventual replacement in 50 years?
I have a feeling that green roofs might be adopted by a few buildings now, and they will be around till the day I die since they last 50 years, and by that time I'll be in my late 70s early 80s. you will see fewer and fewer of them as the reality of keeping a green roof from becoming a jungle roof mount up. I'm all for finding ways to reduce a building's impact on the environment, but green roofs aren't the #1 solution.
And what about the added weight of the storm water? green roofs can eliminate store water runoff? that means the weight of that water is added to the roof... while some structures might be able to handle the weight, I'd say a good chunk of structures WON'T.