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Fast Method to Mimic Soiling and Weathering of Cool Roofing and Other Building Materials





Berkeley Lab scientists led by Mohamad Sleiman, Thomas Kirchstetter, Hugo Destaillats, and Ronnen Levinson have developed an innovative technology that can mimic, in just a matter of days, the effect on new building materials of years of outdoor exposure to atmospheric dirt and variable weather conditions. This technology is of particular benefit to cool roof materials, which reflect a high proportion of sunlight into the atmosphere to reduce the energy and expense of air conditioning while lowering ambient air temperature in urban areas. Currently, the natural deposition of soot, salt, dust and organic matter conspire to degrade the reflectance of surface materials. Manufacturers can design soil-resistant roofing materials, but standards require three years of outdoor testing to gauge how effective a new product may be. This impedes development and investment in these innovative roofing materials.

The Berkeley Lab team addressed this problem by formulating a spray containing the agents that soil roofs. Roof surface soiling is typically a consequence of exposure to soot (black carbon), dust, salts, and decomposed organic debris. The mix in the spray can be tailored to match the environmental conditions of different locales. For example, Arizona roofs are affected mostly by dust; Florida roofs, by organics; and Ohio roofs, by soot.

The technology includes protocols for exposing the surface of roofing samples to ultraviolet light, water vapor, and simulated rain in a commercial “weatherometer” system; spraying the formulated soil mixture onto the surface; and finally subjecting the surface to a final cycle of weathering. Tests using roofing samples exposed to natural outdoor conditions show that the Berkeley Lab technique can accurately mimic the effects of multiyear exposure in as few as three days. The system works on roofing materials such as tiles, asphalt shingles, polymer membranes, metal, and modified bitumen. The technique can also be used to test coatings and other materials designed to reduce the effect of soiling on cool roofs, siding, glass, photovoltaic panels, or automobile exteriors.

DEVELOPMENT STAGE:  Bench-scale prototype

STATUS: Patent pending. Available for licensing or collaborative research.


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