New Design Tool Helps Select the Right Green Roof for Specific Locations

Green roofs, also known as ecoroofs, are growing in popularity as the green building industry continues to expand. These planted rooftops use vegetation and soil over a waterproof membrane to slow stormwater runoff, filter water-borne pollutants, and save energy. Green roofs reduce the heating and cooling energy demands of a building because the vegetation and soil serve as added insulation in the winter, and offer a combination of insulation, shading, reflectivity, and evaporative cooling in summer.

But different climates and building locations require different types of green roofs. The amounts of sunlight, prevailing winds, rainfall patterns, etc. all influence the performance of a green roof. While researchers have looked at how well various green roofs perform, this work has not yet resulted in a system design tool that helps building professionals optimize ecoroofs for different climates and locations. Until now—right here in Oregon.

Professors David Sailor and Graig Spolek at Portland State University are using Oregon BEST funding to develop measuring and modeling methods of green roof performance to design an “energy savings calculator” that will help determine energy performance of a variety of green roof designs deployed in different climatic regions.

“The end result will be a simple tool that building designers and architects can use during the design process to select a green roof that will work best on a specific building,” says Spolek. “And because we’re developing this tool here in Oregon—using local architectural firms for testing—Oregon building professionals will be the first in the nation to have access to it. This will help Oregon advance its position as a national leader in the green building industry and attract related businesses to the state.”

The Oregon BEST funding is making it possible for Sailor and Spolek to invest in new laboratory equipment, including improvements to an environmental wind tunnel that allows heat transfer testing through green roofs while controlling temperature, humidity, sunlight, and rainfall. Baseline data will enable the researchers to build computer models that will result in the energy savings calculator.

“We need more test data for hot and humid climates,” Spolek says. “The funding from Oregon BEST will enable us to gather that data.”

Oregon BEST’s seed funding to this project has already helped the research team win a $150,000 grant the U.S. Green Building Council, one of only 13 projects nationwide selected for funding by the organization out of 215 proposals submitted. “Without the funding from Oregon BEST, we would not have received the grant from the U.S. Green Building Council,” Sailor says.

Deciding whether or not to add a green roof can be influenced by factors other than reducing heating and cooling costs. For example, energy savings is much higher for short, squat buildings than for tall ones, but tenants are happier knowing their tall condo building features a green roof, which could result in higher rental and occupancy rates.

“As Oregon’s reputation in green building design continues to grow, the timing of the Oregon BEST funding couldn’t be better,” says Spolek. “All of Oregon will benefit from this investment in research.”

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