For several years, desert-like plants have been growing on the roof of the Broadway Housing Building to reduce storm run-off that carries chemicals, metals and oil into the water system. Researchers at Portland State are monitoring the performance of these ecoroofs in hopes that the research will culminate in the design of a computer program that would allow building companies to create a model ecoroof and determine the benefits it will provide.
Studying a rooftop environment
For several years, desert-like plants have been growing on the roof of the Broadway Housing Building to reduce storm run-off that carries chemicals, metals and oil into the water system.
Researchers at Portland State are monitoring the performance of these ecoroofs in hopes that the research will culminate in the design of a computer program that would allow building companies to create a model ecoroof and determine the benefits it will provide.
Ecoroofs are used in place of conventional roofing materials and are constructed using a synthetic waterproof membrane covered with soil and a layer of vegetation. Ecoroofs may lower energy usage by creating natural insulation for buildings, and create more vegetation within the city.
The Broadway building at PSU was built with the largest ecoroof in Portland in the fall of 2004.
“The building has become our laboratory,” said Graig Spolek, chair of the Department of Mechanical and Materials Engineering.
Spolek has been monitoring the performance and development of the Broadway Housing Building’s ecoroof for several years through sensors placed beneath the roof when it was built. The research is separated into three sections: evaluation of the roof’s performance, a detailed analysis of the economic benefits provided by the ecoroof, and a determination of how it will reduce energy costs.
Finally, the results of the research will be integrated into software designed by Professor David Sailor, project director and associate professor in mechanical and materials engineering. The software will simulate the ecoroof for potential builders, aiding them in deciding which ecoroof will function ideally for their building. Factors to be considered will be the type of soil used, the type of vegetation planted and the size of the roof, according to Sailor.
According to Spolek, his research is focused on two major points: how much the ecoroof reduces storm water run-off, and how it will lower the energy costs of the building. The energy costs are affected by how much heat is lost or gained through each part of the building, Spolek said. Costs have been lowered about 10 percent for the roof of the Broadway building. Storm water run-off has been reduced about 25 percent, Spolek said.
In a phenomenon called the heat island effect, large cities tend to give off large amounts of heat due to little vegetation and large areas of asphalt, requiring more energy to be used for cooling. Scientists think ecoroofs may help create more vegetation and absorb heat as they became more widely used throughout the city.
Researching the ecoroof directly has some disadvantages, Spolek said, because researchers cannot control the environment in which the roof exists. Weather and temperature cannot be controlled outdoors, so Spolek hopes to create a controlled environment inside a laboratory in which he can study the ecoroof materials further.
Dave Ervin, professor of environmental science at PSU, is researching the economic implications of the ecoroof’s design. This information will help potential builders design ecoroofs in the most cost-effective way.
“We think this is very important because there are more and more ecoroofs being built,” Ervin said.
Ervin said he feels that there is not enough literature on the subject of ecoroof cost effectiveness and aims to build a base of solid economic analysis. This information will be valuable to both academics studying ecoroofs, he said, and those in the building industry interested in converting to green building.
Professor Sailor will bring all of the research together in simulation software, which he has been working on for about two years. The program will model the monthly energy costs of the building depending on factors such as soil depth and vegetation density, and will allow the user to assess their potential ecoroof.
The research includes several collaborating organizations, according to Ervin. These organizations are the Portland Office of Sustainable Development, the EcoWorks foundation, and the Gerding-Elden Development Company. According to Ervin, these companies will aid the researchers by providing external support and allowing them access to their data on ecoroofs.
