Final Report: Regionally Appropriate Sustainable Design: Urban Green Roof Applications for Temperate Continental Climates

EPA Grant Number: SU833194
Title: Regionally Appropriate Sustainable Design: Urban Green Roof Applications for Temperate Continental Climates
Investigators: Hornbach, Dan , Dosch, Jerald , Dickinson, Mark
Institution: Macalester College
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 30, 2006 through May 30, 2007
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2006) RFA Text |  Recipients Lists
Research Category: P3 Challenge Area - Built Environment , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability


The Macalester green roof was installed in September 2006, ahead of the original project schedule, and will be completed with the seeding of native prairie plants in April 2007. A dedication ceremony will occur April 26 which will include an unveiling of an on-site, informational plaque for the green roof and speeches by Mayor Chris Coleman of St. Paul as well as Corrie Zoll, a local green roofing activist. The green roof covers one of nine 1600 square foot pods on the roof of Kagin Commons, a centrally located building on our campus. The Minnesota Building Code requires that 35 pounds per square foot of the structural support of the building be reserved for snow support. This left us only 15 pounds per square foot with which to work. Instead of opting for shallow soil depth, which wouldn’t allow native prairie species to grow, we decided to leave a 10 x 10 foot section in the middle without vegetation. This allowed us to work with 4 inches of growing medium instead of 2 inches. Working with our community partners and facilities management at Macalester, we tore off the existing roof to the deck surface, and retarred/water proofed the surface to insure no holes. Then, with the help of Macalester student volunteers in the final steps, we installed the root barrier, drainage cups, filter fabric, and soil of our green roof.

Our completed and continuing research covers three areas: social implications and community involvement in green roofing and other local sustainability projects, economic benefit to Macalester College, and environmental costs and benefits on a local and global scale. Tours of the green roof are available to community members interested in the project and project leaders remain involved in community organizations and green roof conferences. Students continue to work closely with Macalester facilities management to obtain data for heating and cooling in the Kagin Commons building where the green roof was installed. The control section and the greened section are monitored for ambient temperature. A water quantity measurement device was specially designed for our project needs and a procedure for water quality testing was developed. However, due to our climate and factors of snow and ice, some scientific research involving water data was limited.

Summary/Accomplishments (Outputs/Outcomes):

First of all, we found that a well-established institution like Macalester College is an ideal place for conducting sustainability pilot projects. Community donors are willing and enthusiastic to help because they trust a college institution and know their product will be showcase for years to come. Connections within the community also create an atmosphere condusive to outreach, allowing our research findings and contact information to be very accessible. Our project was both an inspiration and a learning tool for others interested in green roofing.

We recognize that our project was feasible economically, but perhaps only because we were able to obtain EPA grant funding through the college, supplemented by money from our student government and community labor and material donations from our community partners worth thousands of dollars. Funding sources like these are not available to everyone, and the long-term pay off is not necessarily economical.

Temperature monitoring on the roof shows the green roof has effective insulation particularly when there are temperature extremes. The green roof evens out temperature extremes so the heat escaping the building does not vary as drastically as it would on a conventional roof. Monitoring below the surface of the green roof has given us a better idea of the insulation factor while monitoring on the surface has measured impact on urban heat island effect. We predict that during the summer months we will see both better insulation and a reduction in ambient air temperature. Limitations in our research included the ice and snow during winter months that required the removal of our water monitoring systems. Research on water quality and quantity will continue once the ground has thawed and the risk of frost passes.


Though some research currently available does not account for the resource input in green roofing materials and process, we consider the movement and momentum that was built up around the project to be a success.

Green roofs are valuable especially in an urban setting because increased green space is healthy for citizens and has aesthetic appeal as shown by previous urban research.1 In general, colleges and universities serve as great laboratories for sustainability projects. Concentrated resources and community networks create a stable, welcoming environment for donors and provide opportunities for continuous long-term research and project enhancement. Since the current technologies in green roof materials are so new to the Midwest, they are also relatively expensive. For green roofs to be economical, they should be included in building plans of new structures, or retrofitted when a building is due for a new roof membrane. Additional year-round research is needed before any conclusions can be made about the environmental impact of our roof. Important correlations are observable but we are unable to draw any conclusions until plants are growing on the roof and year round monitoring is completed. Water quality, quantity, insulation efficiency, and effect on urban heat island effect must be meta-analyzed. The emissions in tearing up and re-tarring the roof should be considered in addition to the petroleum required to create the materials we used.

The success of our project can be seen throughout the process and in the involvement of so many community partners. It was inspiring for us to see so many people interested in our project, going on to initiate projects on their own campuses because of Macalester’s successful living roof.

Proposed Phase II Objectives and Strategies: Because we would like to have a wealth of research before we can draw real conclusions about the costs and benefits of green roofing, our Phase II project would be to extend this research for another calendar year and further into the future. We would like to green roof six more 1600 square roof pods on Kagin Commons, leaving only the pods with skylights and the penthouse unchanged. Kagin Commons will be almost entirely green roofed if we can reproduce the project we created on our first pod this year. With Kagin Commons almost entirely re-roofed, we can then continue our research with the equipment we have already secured and learned to use to test water quality, run-off quantity, ambient air temperature, and insulation benefits. Our main objective in continuing research is to have concrete data available to the public about the benefits of green roofs here in Minnesota. We want to fuel the green roofing revolution not only on campus but in our community.


Sullivan, William C. “The Fruit of Urban Nature.” Environment and Behavior, Vol. 36, No. 5, 678-700 (2004). Wells, Nancy. “Nearby Nature.” Environment and Behavior Vol. 35, No. 3, 311-330 (2003). Frumkin, Howard. “Beyond Toxicity: Human Health and the Natural Environment.” American Journal of Preventive Medicine. Vol 20, No. 3, 234-240 (2001).

Supplemental Keywords:

green roof, urban heat island, global climate, regionally appropriate design, emissions reduction, community-based, urban habitat, precipitation, college campus, green building design, ecological design, sustainable design, sustainable development, energy conservation, energy efficiency,pollution prevention, smog, nitrogen oxides, sulfates, carbon dioxide, cost-benefit, non-market valuation, monitoring, analytical, measurement methods, environmental chemistry, Great Lakes, Midwest, Minnesota, MN, EPA Region 5, RFA,, RFA, Scientific Discipline, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Technology for Sustainable Environment, Environmental Engineering, energy conservation, sustainable housing, green design, sustainable development, alternative building technology, environmental conscious construction, environmental sustainability, green building design, green roof, architecture

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