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Abstract
Experience shows that reflectance of reflective roofing materials can be significantly reduced overtime as the materials are exposed to varying environmental conditions. Reflectance degradation is undesirable aesthetically as well as for cool-roof performance, and has been difficult to predict. We have conducted a series of experimental and theoretical works since the early 2000s to improve our understandings of reflectance degradation. Roof samples from several field sites in the State of California were exposed for 1.6 and 4 years, and chemically analyzed to obtain the elemental composition of the accumulated materials on the roof samples. The chemical profiles were analyzed to identify variables contributing to reflectance degradation and to develop a predictive model that was used to explain the degradation. Combinations of iron, chromium, and elemental carbons are found to predict the reflectance degradation reasonably well. However, organic carbon (OC) and biomass were found to increase on the samples over time, but OC was not identified by the model as a predictor. It is commonly known that reflectance degradation is a serious problem in humid climates such as the state of Florida, and the reflectance degradation has been linked to the accumulation of biomass on the roof surface. However, the lack of correlation in the California data set suggests that the reflectance degradation caused by microbes is much more complicated than degradation from dust soiling. Some microbial species might not be as detrimental to reflectance as commonly thought. The importance of climatic condition and diversity of microbial community thus needs to be examined systematically. To this day, we have performed metagenomics investigations to reveal the commonality and difference of microbial communities on samples from various climatic regions of the US forming the backbone of the microbial-accelerated test protocol.
Experience shows that reflectance of reflective roofing materials can be significantly reduced overtime as the materials are exposed to varying environmental conditions. Reflectance degradation is undesirable aesthetically as well as for cool-roof performance, and has been difficult to predict. We have conducted a series of experimental and theoretical works since the early 2000s to improve our understandings of reflectance degradation. Roof samples from several field sites in the State of California were exposed for 1.6 and 4 years, and chemically analyzed to obtain the elemental composition of the accumulated materials on the roof samples. The chemical profiles were analyzed to identify variables contributing to reflectance degradation and to develop a predictive model that was used to explain the degradation. Combinations of iron, chromium, and elemental carbons are found to predict the reflectance degradation reasonably well. However, organic carbon (OC) and biomass were found to increase on the samples over time, but OC was not identified by the model as a predictor. It is commonly known that reflectance degradation is a serious problem in humid climates such as the state of Florida, and the reflectance degradation has been linked to the accumulation of biomass on the roof surface. However, the lack of correlation in the California data set suggests that the reflectance degradation caused by microbes is much more complicated than degradation from dust soiling. Some microbial species might not be as detrimental to reflectance as commonly thought. The importance of climatic condition and diversity of microbial community thus needs to be examined systematically. To this day, we have performed metagenomics investigations to reveal the commonality and difference of microbial communities on samples from various climatic regions of the US forming the backbone of the microbial-accelerated test protocol.
Date
7/2012
7/2012
Author(s)
Meng-Dawn Cheng; Karen Cheng; Susan Pfiffner; Joshua New; William Miller; Paul Berdahl; Andre Desjarlais
Meng-Dawn Cheng; Karen Cheng; Susan Pfiffner; Joshua New; William Miller; Paul Berdahl; Andre Desjarlais
Page(s)
1-11
1-11
Keyword(s)
reflectance; reduction; contamination; degredation; microbial
reflectance; reduction; contamination; degredation; microbial