Tag Archives: albedo

A Standard is Born

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.

Video Explains How Reflectivity Can Change Over Time

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.

You can find more great videos at GCCA’s new YouTube Channel.

Climate Change and Geoengineering

There has been a lot of press coverage of the decision by the National Academy of Science to study the feasibility and safety of large-scale geoengineering as a means to address climate change. It is hard to believe that we are at a stage where we must consider such drastic strategies.

Much of the conversation has revolved around the idea of albedo modification — that is, increasing the amount of solar energy reflected into space rather than absorbed by earth. Conceptually, this is the same process that keeps light colored roofs and pavements cooler. However, the scale of the geoengineering being considered is staggering — we are talking huge swaths of the earth brightened by man-made clouds. Since only 1% of earth’s surface is urban, even a wildly successful global cool roofs and pavements campaign would be nearly 70 times smaller in scale than what is under study now. There really is no comparison.

And yet, focusing efforts of deploying more cool roofs and pavements would have a tremendously positive impact on the planet. They help cut cooling energy and peak electricity demand, improve heat resiliency of people living in unconditioned buildings, and cool down communities and help reduce air pollution; all while safely offsetting the warming effect of atmospheric greenhouse gases.

The scientific debate is on about whether we have reached a point where we must consider drastic measures to combat climate change. Either way, we should be taking the simple and affordable first steps to improve our buildings, communities, and planet by installing cool roofs and pavements anywhere it makes sense to do so.

LBNL Develops New Interactive Rooftop Reflectance Map

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.

You can explore LBNL’s new interactive map HERE.

Cool Roofs Studies are in the News

New reports from GCCA & ACEEE, and the Georgia Institute of Technology find that many cities are developing strategies to reduce excess urban heat, and that states, neighboring jurisdictions, utilities, and building owners are helping to mainstream these practices.

The first study comes from the Global Cool Cities Alliance (GCCA), and the American Council for an Energy Efficient Economy (ACEEE), in which they surveyed the policies of 26 North American cities.   E & E Publishing’s ClimateWire raised a few points we thought were worth noting, in Cities Take Steps to Address Extreme Heat

Several cities across the United States and Canada are now taking steps to mitigate local heat and prevent future warming, according to a new survey by the American Council for an Energy-Efficient Economy (ACEEE) and the Global Cool Cities Alliance (GCCA).  Of 26 medium and large cities, two-thirds cited extreme heat events and an increased number of high-heat days as the trigger for adopting policies to address the heat island effect.

. . .

Installing reflective and light-colored surfaces on walkways, roads and roofs is one of the most effective ways to address the heat island effect.  For instance, U.S. EPA research shows that conventional asphalt can reach 120-150 F in the summer, while reflective pavement stays 50-70 degrees cooler.

. . .

More than half of the 26 cities surveyed said they have requirements in place for reflective and vegetated roofing on private-sector buildings.  And nearly every city had policies to increase tree canopy and improve stormwater management.

ClimateWire also reported on a new study out of the Georgia Institute of Technology in which researchers looked at Phoenix, AZ, Philadelphia, PA and Atlanta, GA, and found that white roofs, reflective pavement and trees can counteract temperature increases in cities and save lives.   From Rising Temperatures Are Deadly, But Urban Cooling Fixes Can Counter Threats

[T]he researchers modeled how the three cities would respond to a minimum green space ratio on land parcels, setting a floor for areas covered with grass, gardens or trees. Vegetation tends to have a cooling effect by circulating moisture in the air that draws away heat during evaporation. Tree canopies also provide cooling shade.

The team also modeled how Phoenix, Philadelphia and Atlanta would behave with more reflective streets, sidewalks, parking lots and rooftops. Higher reflectivity, or albedo, means the area absorbs less sunlight, thereby lowering the temperature.

Stone and his collaborators then overlaid a health impact model. They found that combinations of increased vegetation and albedo could cut into projected increases in heat deaths, reducing them between 40 and 99 percent. “On average, we reduced the rate of increase by about 60 percent,” Stone said.

. . .

Groups like the Global Cool Cities Alliance are now trying to get cities to adopt these adaptation strategies, pitching them as a way to protect public health. However, it’s slow going, given that cities around the country address heat vulnerability differently, if at all.

You can find the full study HERE.

This report parallels a recent GCCA report, which looks at Baltimore MD, New York, NY, and Los Angeles, CA, and shows how reflective roofs and vegetation can cool air temperatures and save lives.

Note: Access to the ClimateWire articles is limited to subscribers.

cool urban initiatives and synoptic climatology

We at the University of Miami’s Synoptic Climatology Laboratory have just completed a study to determine how an increase in albedo and vegetation within an urban area will contribute to a healthier city. We used a novel approach: determining whether cooling associated with these urban changes will alter the air mass type over a city from one that historically leads to negative health outcomes to one that is more benign. We did determine some important improvements. To see the manuscript, please go to this site:https://www.coolrooftoolkit.org/wp-content/uploads/2014/07/Three-City-Heat-Health-Report-FINAL.pdf

Any comments are welcome!

Thank you, Larry Kalkstein