Rerun: Cool surfaces: Reflecting heat and reducing emissions, with Ronnen Levinson

Two women sit on a patch of white-painted parking lot. One looks at a notebook while another manipulates technology. A technology carrying case is seen off to the left.

Image caption: Sharon Chen and Ana Paula Werle of the Berkeley Lab Heat Island Group use a reflectometer to take measurements of cool pavement solar-reflective coatings. Image Credit: Roy Kaltschmidt/Berkeley Lab.

Script by: Sophie Wenzlau Audio by: Wangyuxuan Xu Blurb by: Elizabeth Shertinsky

What is a cool surface?

Cool surfaces are roofs, walls, or pavements that are generally light-colored and highly reflective. When sunlight hits a white surface, its rays bounce off the surface rather than being absorbed, and are reflected back into space. Darker surfaces tend to absorb sunlight, trapping heat. Cool surfaces release this heat back into the atmosphere and space. 

What are the benefits of switching to a cool surface?

Something as simple as painting the roof white has the potential to create major benefits for our planet and its people: 

Climate changeCool surfaces reflect heat in a warming planet. Every 1000 square feet of dark roof replaced with a cool roof cancels out the warming effect of 10 tons of greenhouse gasses. In addition, reducing the need for electricity to cool buildings reduces fossil fuel emissions. 
Heat wavesClimate change increases the number and strength of global heat waves. Cool surfaces can help mitigate this heat, especially in low-income urban communities disproportionately affected by heat waves due to living in dark city infrastructure. One study found that just a 10% reflectivity increase could reduce heat wave deaths by 6%. 
Energy savingsCool surfaces reduce the need for electricity to cool down a building. One analysis concludes that if all commercial buildings in US cities switched to cool surfaces, the US could save nearly $1 billion per year. Energy cost savings could especially help low-income families. 
Strengthens electric gridLess energy use for cooling means less strain on the grid. This means less blackouts on very hot days, and more energy left to charge electric vehicles and other appliances running on renewable energy. 
Air qualityCooler air contributes to less smog pollution in cities. This makes cities even more resilient against heat waves and their health impacts.

Potential cons of cool surfaces

  • Sun reflecting off of cool surfaces could cause uncomfortable glare and brightness.
  • Because they are white, cool surfaces can have a dirtier appearance, requiring greater upkeep.
  • Some research indicates that reflected sunlight from cool pavements could increase heat levels for pedestrians.

Despite these issues, cool surfaces have a large set of potential benefits overall. 

About our Guest

Dr. Ronnen Levinson is leader of the Heat Island Group at Lawrence Berkeley National Laboratory (LBNL). The Heat Island Group develops cooling strategies for roofs, pavements, and cars to cool buildings, cities, and the planet. This work involves developing cool roof, wall, and pavement materials, improving methods for the measurement of solar reflectance, and quantifying the energy and environmental benefits of cool surfaces. Levinson advises policymakers, code officials, utilities, and building rating programs about cool surfaces. He earned a B.S. in engineering physics from Cornell University, and an M.S. and Ph.D. in mechanical engineering from UC Berkeley. 

Further Reading

Cool Roofs and Cool Pavements Toolkit from the Global Cool Cities Alliance 
Shickman: US Perspectives on Cool Surfaces
Hot Enough For You? Cooling The Worsening Urban Heat Island
On-the-ground guidance for L.A.’s far-reaching climate strategy | UCLA


Transcript

Ethan: I’m Ethan Elkind, and you’re listening to Climate Break: Climate solutions in a hurry.  Today’s proposal? Using reflective building surfaces to cool urban areas by redirecting sunlight back into space. We spoke to Ronnen Levinson, a staff scientist at Lawrence Berkeley National Laboratory, about how reflective, or “cool,” surfaces can combat climate change by reducing heat and lowering energy consumption in buildings.

Dr. Levinson: If your goal is to slow the rate at which the earth is getting warmer, then surfaces that reflect more sunlight than usual—for example: white roofs, light colored pavements, light colored walls—by rejecting some of that incoming solar energy back out to space, they reduce the heating of the atmosphere. So, you can get a global cooling.

A cool surface can lower the air temperature outside in a city and inside your home or office by simply reducing how hot the outside of the building is, which will keep your building cooler.

Ethan: By lowering building temperatures, reflective surfaces can reduce the need for energy-intensive air conditioning, resulting in lower energy consumption, fewer emissions, and cost savings for building owners.

Dr. Levinson: So, if you’re thinking ahead to how to futureproof your home to the terrible trifecta that we have of heat wave, power outage, and wildfire smoke, then a cool surface is a no-brainer.

Ethan:  To learn more about reflective building materials and how to add them to your building, visit climatebreak.org.

Rerun: Cool surfaces: Reflecting heat and reducing emissions, with Ronnen Levinson