The afternoon sessions on Friday, March 12th will feature a number of local experts and topics.
Ecoroof Research and Monitoring
Friday, March 12th, 2:30 - 4:00 pm
Greenroof Soil and Water Quality - Changes in Runoff Water Quality When Biochar is Mixed into a Greenroof Soil
Debbie Beck, Portland State University
Greenroof growing media needs to be designed to insure low concentrations of nutrients in the stormwater runoff. One soil amendment, biochar, was evaluated for its ability to retain nutrients in greenroof soils. The biochar used in this study was made from the pyrolysis of tires, a carbon-net-negative process, and resulted in improved water quality of the runoff.
Runoff from prototype greenroofs was collected and evaluated for water quality. Greenroofs containing biochar showed significant increases in retention of nitrogen, phosphorus and organic carbon. The addition of biochar to greenroof soil appears to be a sustainable way to retain nutrients in the soil and improve water quality by reducing nitrogen, phosphorus and organic carbon concentrations in the runoff water.
Stormwater Monitoring of Three Ecoroofs in Portland, Oregon
Tim Kurtz, PE, City of Portland BES
The City of Portland, Bureau of Environmental Services (BES) has become increasingly committed to using Green Solutions, also known as Low Impact Development (LID), to manage urban stormwater runoff. Ecoroofs have become a primary option for reducing roof runoff into sewers and streams. Currently, all ecoroofs are considered equal in their ability to manage stormwater. But differences in soil media type, soil media thickness, and irrigation are thought to play a significant role in ecoroof performance. In an effort to ensure ecoroofs provide a reliable benefit, data is being gathered from several ecoroofs to determine which design and maintenance variables are most important to maximize stormwater retention. Monitoring data is available for three Portland ecoroofs with unique designs in terms of soil media, thickness, and maintenance practices.
Energy Performance of Ecoroofs - the Role of the Roof in Affecting Building Energy and the Urban Atmospheric Environment - David J. Sailor, Ph. D, Portland State University
Ecoroof systems can have wide-ranging impacts on the urban environment. One of the most fundamental impacts of ecoroofs is the way in which they modify the rooftop energy balance. Specifically, ecoroofs impact every aspect of the surface energy balance. This includes shading of both long and shortwave radiative exchange, modification of convective heat transfer, evaporative cooling associated with evapotranspiration, and conduction/storage of heat in the growing media. This impact of the ecoroof on the surface energy balance changes over the course of the day and across seasons, and as a result is far more complex than the effect of any typical construction material. Thus, energy analysis of ecoroof performance requires sophisticated techniques, and sometimes leads to unanticipated results that impact the optimal design of such systems.
This presentation will offer an overview of the complexities of the energy balance of ecoroof systems. It will explore impacts of roof design characteristics on building energy consumption for both heating in winter and cooling in summer. It will also discuss the broader implications of the rooftop in affecting the urban thermal climate (urban heat island). The presentation will conclude with an example of a current research project in which the combination of ecoroof systems and rooftop photovoltaic power generation is being explored with a focus on potential system interactions and synergies.
Portland's Shift to a Sustainable Future: The Role of Ecoroofs
Friday, March 12th, 4:00 - 5:30 pm
Dan Vizzini, City of Portland Environmental Services
Tom Puttman, David Evans and Associates
Tom Liptan, City of Portland Environmental Services
While ecoroof and greenroofs are not new ideas, implementation in the U.S. and, even more so, Portland, is relatively short-lived. Tom Liptan, Ecoroof Technical Program Manager with BES, installed the first ecoroof in Portland in 1996. Fourteen years later, the City of Portland is boosting implementation of green infrastructure practices, including a target of 43 acres of ecoroofs by 2013. This session will provide an overview of how the City of Portland has made this shift, why it makes sense economically to incorporate ecoroofs, and how these changes will influence the form of our city.