The Sustainability of Green Design

A few weeks ago I attended the sixth annual Green Roofs for Healthy Cities Conference in Minneapolis. It was very well organized and in a great location. Minneapolis is really pushing the envelope to become a Green City and a leader in sustainable urban design: their new Public Library was designed with a Green Roof and they are offering rebates on utility bills for stormwater retention on-site. While at the conference, I met a ton of folks from around the US as well as around the world, such as Dr. Nigel Dunnett (UK), Sidone Carpenter (Australia),  Paul Kephart (of Rana Creek),  folks from EarthPledge, Rosalind Haselbeck, the list could go on and on.

A small green roof along Main Street Park, a developing area along the Mississippi River in Minneapolis.

One of my main goals in going to the conference was to bring back some Green Roof inspiration and motivation to add to our interdisciplinary practice at Sasaki Associates. As a mix of architects, landscape architects, urban designers, and planners, we have a responsibility to be be a model for what is possible for sustainable and green design. To me, this means maximizing the sustainability of our projects while minimizing their impacts; and Green Roofs have the potential to play an enormous role in this.

When I returned from the conference, I stated to some co-workers that "I wanted to have a green roof project in the office within the year." Well, the old cliche of you'd better be careful for what you wish for certainly came into play: Low and behold a project has materialized. Thanks to the great job that a Sasaki architectural team had with Montior Group in San Francisco, The Federal Reserve Bank has asked Sasaki to come up with a design proposal for their mature roof garden. Constructed in the 1970's, the roughly 12K sq.ft. open space is lush with a diverse palette of plant material and wildlife, such as birds.

The facilities and design group at the Fed Res Bank is concerned about the aging waterproofing and has decided to replace the membrane. When they do this, it will envolve removing all of the soil and plant material from the roof, re-waterproofing the topping slab, and then replanting the entire roof. What they have asked of us (Project Team: Richard Tepp (Architect), Francesco Francesco Mozzati (Architect), and myself) is to create a space on the roof that will allow for evening and daytime events during inclement weather. Downtown San Francisco can become quite foggy, windy and cold. It is fantastic that the Federal Reserve is interested in maintaining and improving the usability if its green space.

This raises the question of how sustainable is "being green?" I attended a discussion session during the GRHC Conference that focused entirely on this topic. While the Federal Reserve Bank is being green in maintaining its roof garden and improving it as an amenity for the workforce in the building, having to pull everything up in order to re-waterproof is certainly not sustainable. Their concern about the waterproofing is certainly valid. I can't blame their concern about the potential for water intrusion into the floor below; especially given that the current membrane was installed over 30 years ago (when green roof projects were pretty new in this country). By replacing the membrane now, they are doing preventative maintenance - a wiser and less expensive solution than waiting until the membrane fails.

But there are trade offs for this: removal of the mature trees and shrubs on the roof (some of which are more than 20' tall), the labor involved in having to pull everything out and off of the roof to create a clean slate on which to install the new membrane, etc. Removing and replacing large quantities of material on a fourth floor roof is no easy feat, and can not be done using the service elevator (a crane will most likely be needed). It seems the staff at the Reserve Bank are very interested in doing what is possible to increase the sustainability of this renovation project, and I'd like to propose a series of strategies to help with this (such as recycling materials, boxing up some of the plant material to re-use, chipping other existing plant material to use as mulch, the potential for rainwater harvesting and storage for irrigation, bringing more passive heating/cooling strategies to the space, etc.).

The focus of our sustainable discussion during the GRHC conference revolved around more specific points about the green roof industry and the amount of new products that are appearing on the market: How sustainable are the liquid applied membranes (many of which are PVC based products), or the plastic drainage composites, the intensive irrigation regimes needed to keep things physically green during our dry summer climate, the chemical fertilizers used to keep the plants healthy in small soil volumes, or the fuel burning cranes, pressure washers, leaf blowers, lawn mowers, etc. that are needed for installation and maintenance of these roof gardens?

I think that a big part of the answer to this lies in the hands of designers. We must be prudent about the products we specify and the spaces we create. By specifying "greener" products (such as recycled plastic drainage composites or non-pvc-based membranes), we can influence product manufacturers to create sustainable products. Additionally, we must be aware of the long-term efforts that are involved in keeping these spaces going by creating designs that don't need a weekly "mow-and-blow." Also, consider the long-term inevitable implications maintenance, repairs, or even the replacement of things as time goes on. One can't expect plants or certain materials to last forever.

"Sustainability" and "green design" don't necessarily go hand in hand. You can build green without being sustainable, and vice-versa. What are the benefits and drawbacks for implementing a particular design? The goal should be to achieve a net positive result in order to maximize the environmental benefits. It is great to imagine a project without any environmental implications, however this is most likely rare if possible at all. By creating spaces that result in a net positive effect, we hope that the collective total of such projects will amount to something bigger and more impactful - a synergistic overlay - that will truly change cities and the way in which we live in them.

Comments

[jim jacobs]

I certainly understand, and agree, with your concerns for what's really "sustainable". However, your approach and early conceptual thinking for material reuse, etc. deserve serious discussion and review with the client.

[Leigh]

What a great concept. It's good to know there are cities and individuals with an eye on the environment.

[john biggs]

sounds like a great project, even with the ethical/technical questions. There are many buildings here in Bucharest that could potentially have green roofs. Sounds like Bucharest could use Sasaki.