Steven W. Peck, Bill Browning and Catherine O. Ryan
Interview, Q/A, Green Roofs, Regenerative Design, Net Positive, Energy, Architecture
A leader in regenerative and netpositive design, Kirstin works with owners, cities and integrated teams to create living, resilient built environments where people and ecosystems thrive together. She has led some of the most cited studies on green roof performance and cost-effectiveness for clients such as the US GSA, Walmart and City and County of San Francisco.
After over a decade at Arup delivering sustainable office, mixed-use, civic and education projects, Kirstin launched Bio Studio, an ecological design consultancy based in the San Francisco Bay Area. Kirstin knows more about the economics of green roofs than just about anyone, and I was fortunate to catch her at her home office for this edition of On The Roof With.
Steven W. Peck (SWP): Kirstin, you've been involved in a number of very important economic studies about green roofs for both public and private sector clients over the past decade? Many of the benefits of green roofs are context specific, both in terms of the objectives for the green roof on the building and the policy context of the jurisdiction. Generally speaking from a private sector perspective, where does the business case for green roof investment principally lie - in savings, revenue generation or both?
Kirstin Weeks (KW): I would say that the business case depends heavily on context. All green roofs will tend to produce returns like building energy savings and protection and life extension of the roof membrane, saving money on reroofing over time. But some of the biggest potential returns come from human experience. In an average office, for example, the investment made in peopleâ€™s salaries and benefits might be 100x the cost of utility bills. Studies have repeatedly shown increased satisfaction and productivity when people have views of nature. Taking a short break in a natural setting can reduce stress levels for hours afterward. So if a green roof is visible or accessible, weâ€™ve seen that the small uptick in productivity has the potential to pay back the entire investment in the green roof in a year or less, whereas the utility savings would tend to take decades. Another scenario where green roofs can pay back quickly is in new buildings that are subject to stormwater management or open space regulations. In some policy environments and on certain sites, it is actually cheaper to build a building with a green roof than to meet the regulations without one.