GCCA Board Member Ronnen Levinson just announced the publication of ASTM D7897-15, ‘Standard Practice for Laboratory Soiling and Weathering of Roofing Materials to Simulate Effects of Natural Exposure on Solar Reflectance and Thermal Emittance’.
This practice was developed and shepherded through ASTM by the LBNL Heat Island Group and by Concordia University, with support from DOE’s Building Technologies Office, and from many industrial and academic partners. It will be used to accelerate the development and deployment of cool roofing materials, and has already been accepted for interim rating of roofing products by the Cool Roof Rating Council (CRRC) and by California’s Title 24 Building Energy Efficiency Standards. The CRRC and LBNL will offer courses at LBNL next month to train and certify test laboratories. Research is underway to adapt the method for use in China, India, and Europe.
While they work with the Berkeley Lab News Center to prepare a release, you can read this earlier write-up describing the acceptance of the practice by CRRC and CA Title 24. You can also learn more about the method itself in the first half of this eight-minute Science at the Theater talk, Cool Roofs Though Time and Space, and in their 2014 SOLMAT article.
GCCA Board Member and researcher at the Lawrence Berkley National Laboratory’s Heat Island Group, Ronnen Levinson, explains how the reflectivity of cool roofing materials can change over time in this new video. He also introduces LBNL’s new California Cities Albedo Map, which estimates the reflectivity of roofs in five California cities.
Scientists at the Lawrence Berkeley National Laboratory (LBNL) have created an interactive map that displays the solar reflectance (or albedo) of individual roofs in five major California cities – Bakersfield, Long Beach, Los Angeles, San Francisco, and San Jose. This is the first time scientists have attempted to map the reflectivity of entire cities.
A white / high-albedo cool roof reflects 80% of the sun’s heat, decreasing solar heating of the building. This reduces the need for air conditioning and lowers energy bills. Cool roofs could also partially counter increased urban temperatures brought on by climate change.
This map allows users to zoom in on a specific rooftop to see how it compares to the albedo of a white roof, or other roofs in the city, and is designed to help cities develop policies that could lead to cooler cities.
Ronnen Levinson, head of LBNL’s Heat Island Group and Board Member of the Global Cool Cities Alliance says this new map can be a useful tool for cities:
To assess these potential benefits for a particular city, we need to measure the reflectance of its roofs with good spatial and spectral resolution. Our map helps bring this into focus.