More ways to cut car emissions: reflective glass and paint

Most of the effort to reduce greenhouse gases from cars has focused on improved fuel efficiency, low-carbon fuels, and alternative engine types like hybrids and plug-in vehicles. These approaches will be critical to meeting GHG targets established in California’s landmark global warming solutions law, as well as similar goals proposed in federal legislation.

California is taking this work a step further with a little known initiative called Cool Cars. The program is studying subtle ways to reduce car emissions by rejecting solar heat gain through improved auto glass and paint. In hot weather, these techniques will cause car interiors to heat up less and thus require less air-conditioning. The savings are significant as a car running with the air conditioning off can be 20% more efficient than a car with it on. If the improvements are built into the glass and paint, drivers won’t experience any loss of comfort.

California’s first step is a draft regulation that would require automakers to start using solar management glass for windshields, side and rear windows in the 2012 model year. New glazing technology can bounce solar rays away from the car without causing glare for other drivers on the road, or can absorb energy and release most of it away from the car. State regulators estimate that the new glass could save over 500,000 metric tons of carbon dioxide per year by 2020, and over one million metric tons per year by 2040.

The state is moving at a slightly slower pace to require new cars to be painted with new reflective pigments. Chemists at various car-related companies are improving paint formulas so that they can reflect the non-visible solar energy more than standard car paints now in use. Once certain technical issues about paint durability are worked out, California could eventually mandate that such reflective paints be standard on a new generation of cars. In the future, the ideal black paint could perform nearly as well as today’s common white paints.

The state doesn’t want to get into the business of telling citizens what color car they can or can’t buy. Last month, the right-wing blogosphere (Limbaugh, et. al.) erupted when some commentators mistakenly alleged that California was about to ban black cars. Beyond correcting the record here, I am curious to know how consumers would respond to an education campaign to steer car buyers towards lighter paint colors. Do you think that in the interests of fighting climate change people would shift their preferences to lighter hues?

For reference, here’s Dupont’s latest market data on automotive colors:

Full disclosure: I own a black car. Among the things I like about my 17-year-old Honda is that the black color hides dirt. When the air conditioning stopped working ten years ago, I chose not to fix it. Do I get enviro-points for this personal sacrifice?

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  1. Greg Grothaus - April 14, 2009

    Instead of legislating that you must buy a white car, why not just incorporate the color of the car into the credit that a car company receives in CAFE fleet standards. This way, the car company can maybe choose to price white cars a little lower to encourage adoption or simply make a few more of them to make the other colors more scarce. Would be a subtle consumer clue.

  2. Adam Stein - April 14, 2009

    By the way, Stern is lying about driving a Honda. He gets around in a solid gold Chevy Impala. The reason it doesn’t have air conditioning is that he ripped it out to make room for the speakers.

  3. Amy - April 15, 2009

    I think that more reflective (bouncing) glazing & paint are an excellent idea.
    My car is black and in the winter it abosorbs the heat wonderfully. In the summer, it is beyond an oven, but I love to drive with the windows open and hardly ever put the a/c on.
    Awhile ago, I thought it would be great to put a light color (white) cover on the car for reflecting the sun in the summer, that could be used while driving, or when the car is parked.
    Another idea similar to color changing straws or those toys that change color when exposed to a different temperature would be a color changing car. If the paint could change color to dark in the winter for warmth, and white for summer or warm climates it would be a great innovative idea. Possibly by stimulating the car exterior with a slight electric grid (like heated radiant floors) it could produce enough cooling power to change the color of the car. It could be powered by a curved solar panel on the roof of the car, or simply run off the car battery.

  4. Paul S. - April 15, 2009

    Yes, you get points for not turning the AC on, but you are a rare case.
    Tho’ I live in New England, I’ve always owned white or off-white cars specifically because they are cooler in the summer.
    I agree with Greg: white or light colored cars should be cheaper to buy, encouraging dealers to push them and buyers to buy them.

  5. triffel - April 15, 2009

    I’m glad I’m not a cop!

  6. Mike - April 15, 2009

    As someone who works for an ink and pigment manufacturer, I can tell you that the cost for thermochromatic pigments is through the roof. Extremely expensive, thus you only see it used in rare occasions or in very small coverage.

  7. Albert - April 15, 2009

    Painting just the roof portion of the car a reflective white color would cut down on 90% of heat absorption into the cabin. Minis and Toyota FJ Land Cruisers make it hip to have white roofs.
    I bought a silver Insight (currently at 66.2mpg), thinking that silver reflects almost as effectively as white (Insights didn’t come in white). Additionally, the windscreen, side windows and glass hatch on an Insight are made of a heat-reflective material. It makes a big difference in the sun. Why aren’t other manufacturers adopting Honda’s technology?

  8. Liz - April 15, 2009

    I remember reading something about solar paint–why can’t we harness the power of the sun to help run our cars instead of just deflecting it away?
    Just a question–does rolling down the windows make your car less aerodynamic and cut down on efficiency (mpg) or is that just an urban myth?

  9. Adam Stein - April 15, 2009

    Not a myth, although the actual effect is highly dependent on the type of car you drive and the speed. In general, it is probably better to use the A/C at highway speeds than to roll down the windows. At lower speeds, windows down might be better.

  10. Albert - April 15, 2009

    Above a certain speed (around 35-40 mph) wind drag becomes a factor. It’s not a myth. The higher the speed, the more wind resistance the vehicle has to overcome, thus, more energy needed. Rolling up the windows on the highway raises efficiency because the closed body creates a more slippery shape.

  11. antfaber - April 15, 2009

    If car manufacturers buy a lot of it, wouldn’t the price come down, due to economies of scale?

  12. Mike O'Brien - April 15, 2009

    In my world of green buildings there is a similar discussion going on about the merits of “cool roofs”. A cool roof reflects more of the infra-red wavelengths, or heat gain, in sunlight. It also has higher thermal emissivity, that is, it re-radiates the heat it absorbs more quickly.
    The most effective cool roofs combine improved solar reflectance and thermal emissivity. Surprisingly, color isn’t as big a factor as might be expected. Cool roof products are available in a fairly wide range of colors.
    In buildings, one of the variables in glazing is its “Solar Heat Gain Coefficent” or SGHC. By law this rating is included on all residential window labels. Manufacturers can tune the low-emissivity coatings on double-pane windows to control how much solar infra-red passes through the glass. Usually, windows that have a low SGHC are sold in hot climates to help reduce unwanted solar gain and reduce AC loads.
    Since these ideas already work in buildings it seems like they make sense for cars too.

  13. joumell - April 15, 2009

    A friend of mine owns a honda, and it really gets hot at noon that the a/c system cannot cope up. But when i retrofilled his a/c with hydrocarbon instead of r134, his car get supercool even at noon. And to boot, the operating pressure , high side, went down from 215-225 to just 150-175psi. You get a colder car with less gas consumption.

  14. Airport Taxi Phoenix - April 16, 2009

    Personally, I don’t think the color of one’s car can contribute in any way to stop the worsening climate. Using renewable energy will.

  15. Peter H - April 27, 2009

    so ho hum really…………I’m Australian and about 70% of cars are white and of the remaining 30% about 10% [ from memory] is metallic silver or very close to that hue, the remining 20% is a mishmash of seasonal colours.
    In our warmer to hot weather why would you want a dark coloured car??? When you return to a white car in summer it is hot but NEVER as hot as a dark colour!!
    As for reflective type paints…..add some nano technology into the mix for a dirt shedding finish. THAT is a real plus; think of the water not required for washing…..what an environmental bonus. Already available for building paint finishes.

  16. Sandy - April 30, 2009

    I have my car in metallic silver colour which heats up in summer and makes it impossible to drive w/o AC.
    I am thinking of painting the roof of the car in either of the two – pure white or reflective shiny silver (like chrome) colour.
    My question is which one would act as a better reflector of heat – white or shiny silver like chrome ?
    Kind regards.
    fitsandy@gmail.com