What will the future of green roofs look like? Will it be some variation on the “starchitect” green roof at the California Academy of Sciences (CAS), above, multiplied many times over?
Probably not. Sure, it’s stunning, but the CAS roof is also relatively high maintenance. Correct me if I’m wrong, but I always thought the point of green roofs was that they would be mostly self-sustaining—not needing any irrigation beyond plant establishment, nor weeding, mowing, or fertilizing. The CAS roof, however, has a pop-up sprinkler system that, given San Francisco’s dry seasons, will probably have to be used in perpetuity. And partly because of the plant choices, the roof must be frequently hand weeded and fertilized.
No question, green-roof “starchitecture” has its place in today’s building environment, because the green-roof movement is still just gaining a foothold in this country. Doubtless many Americans are unaware that such systems even exist. So it’s important that these early “demonstration” green roofs be eye-catching. But we should also understand that demonstration projects are mainly there to promote the genre, not to serve as prototypes for what will be built in the future.
Take the Chicago City Hall green roof as another famous example. I have personally visited it. It is stunning and inspiring—like a patch of Midwestern prairie perched above the city, abloom with wildflowers and buzzing with dragonflies and other insects amid the tall, waving grasses. The exposure it has garnered has done a great deal to bring attention to the genre, but its $2.5 million price tag disqualifies it, too, as a model to be emulated.
How can we progress beyond a few high-profile green roofs sprinkled here and there in a few of our cities? Scale is what will make green roofs work as an ecosystem service. If they are really to ameliorate stormwater runoff and the heat island effect, we need whole city blocks that are green roofed corner to corner. We need lots of multiacre green roofs on big-box stores on the urban fringe. What will it take for these to happen?
A few local governments are offering incentives for buildings with roofs that soak up rain and keep it from overloading the city sewer system. That’s part of the solution. We also need low-cost, foolproof systems put in by experienced installers who know green roofs because that is the core of their business. But if green roofs become a streamlined, mass-production enterprise dedicated to greening America’s rooftops, will designers then have a role?
Landscape architects who continue to have a role in the future will be those who have proved they are up to the job. With green roofs, a lot seems to fall through the cracks between the drawing board and the final product. Landscape architects who get serious about this project type will have to learn about the technology, test their products, and pay attention to what happens on the job site—and afterward. Do green roofs present enough of an opportunity for landscape architects to make that kind of learning curve worth the time and effort?
J. William “Bill” Thompson, FASLA
Editor, Landscape Architecture magazine
Send in your ideas. Use the comments to post examples of good, low-cost green roofs.