Of all the low-impact-development techniques and green infrastructure strategies in the toolbox, the one that gets put to use least often, at least in the US, is perhaps the green roof.
There are reasons for this. Green roofs usually cost more than other measures like bioswales or rain gardens, and not every building can be retrofitted for one. In addition, although a green roof can help reduce peak flows, it doesn’t infiltrate water as other LID techniques do, instead holding only what it can in the growing medium and reducing stormwater through evapotranspiration.
As this 2008 Stormwater article describes, there are different types of green roofs, and more and less expensive ways to construct them. Intensive green roofs have a thicker layer of growing medium, can support a variety of plants—sometimes even trees—and better lend themselves to public access, while extensive green roofs have a shallower growing medium but are lighter in weight, usually cost much less, and require less maintenance.
A website dedicated to green roofs highlights outstanding projects, such as this one atop Mercy Medical Center in Baltimore. For each project, details of the construction—size, whether the green roof is intensive or extensive, slope of the roof, cost—are included, and the architects, designers, contractors, and materials suppliers are listed. The site also carries advertising and links to various suppliers.
Green roofs provide benefits beyond stormwater, including helping to insulate buildings and reducing the urban heat island effect. And they look good. Have you incorporated a green roof as part of a larger project, or is there a particularly good example in your area?
Upcoming Forester University Webinars
April 5th, 2012
for Surface Water Quality (new date added)
Constantly influenced by natural eutrophication, direct human impact, and a changing climate, surface water is a scarce natural resource needing effective protection. Join Shahram (Shane) Missaghi to explore the function and benefits of BMPs in protecting surface water, and examine three key criteria to insure their successful implementation: water, soil, and climate Read more...
April 12th, 2012
Water Auditing 101
Reduce your water waste and cost! Join Troy Aichele, LEED AP (O+M) of Aichele and Associates LLC to explore the key attributes, uses, and efficiency/cost opportunities of water audits. Aichele will lead a discussion of what a water audit includes, who performs the audit, where and when they should and can be performed, and the opportunities that exist in performing a water audit. Join us and gain an understanding of the potential savings possible, rebates available, and how quickly this unobtrusive work can be implemented from audit to installation to optimize your water use and minimize your cost. Read more...
April 18th, - May 25th, 2012
Sediment and Erosion Control
Master Class Series
Join industry expert and bestselling author Jerald S. Fifield, Ph.D., CISEC, CPESC and Tina R. Evans, PE, CISEC for a comprehensive 6-part online master class and workshop series (0.9 CEUs / 9 PDHs) exploring the ins and outs of effective sediment and erosion control plan design and review based on Fifield’s recently released 3rd edition of the bestselling manual Designing and Reviewing Effective Sediment and Erosion Control Plans (included in your Master Class Series package).