The ASLA (American Society for Landscape Architects) green roof project site lets you follow this particular roof from concept through execution. (There's actually a live web cam, so you can even watch the breeze hit the grass if you're so inclined.)
Their fact sheet generalizes the specs: this roof could accomodate up to 40 lbs./SF and used a dual-wave design to hide the HVAC system. And even though the cost details are a vague sketch, at $20/SF on the high end, the cost relationship of green vs. traditional is approximately 2 times, with a corresponding expectation that the green roof will last twice as long while reducing heating and cooling costs by 10-20%.
Don't stop there if you're seriously considering green roof technology: Check out the schematics from Michael Van Valkenburgh Associates, Inc., the project's architect.
Photo credit: ASLA
