|Infrared reflective glass is the more efficient—and costly—technology for reducing vehicle cabin temperature. Click to enlarge.|
The California Air Resources Board adopted a regulation that will require new cars sold in California starting in 2012 to have windows that reflect or absorb heat-producing rays from the sun. This will help keep cars cooler, increase their fuel efficiency and reduce greenhouse gas emissions.
Cooler cars mean less air conditioning thereby increasing fuel efficiency and preventing about 700,000 metric tons of carbon dioxide from entering the atmosphere in 2020—roughly the equivalent of taking 140,000 cars off the road for a year.
|Solar absorbing glass absorbs the sun’s energy, reflecting little. Click to enlarge.|
The scoping plan for AB32, California’s climate change legislation, originally had proposed a cool cars measure based on reflective paints. ARB dropped consideration of that “cool paint” regulation after determining that paint technology was not ready. (Earlier post.)
Among the concerns were that GHG reductions from reflective paint were much less than anticipated; black reflective paint was not commercially acceptable (the earlier regulation had prompted a flurry of incorrect speculation that ARB was about to ban black paint); durability concerns re: chipping and scratches; and lack of compatibility with emerging paint processes that reduce emissions during paint application.
ARB staff had identified glass technology as another way of reducing vehicle cabin temperature and A/C use.
This is a common-sense and cost-effective measure that will help cool the cars we drive and fight global warming. It represents the kind of innovative thinking we need to reduce greenhouse gas emissions from our vehicles and steer our economy toward a low-carbon future.—ARB Chairman Mary Nichols
Broadly, there are two types of solar control glass technology:
Infrared Reflective Glass requires the window to be laminated. It contains a reflective coating sputtered between pieces of glass, or uses a coated film placed between the two pieces of glass. This type is best for limiting solar energy going into the vehicle. The total energy which enter the vehicle is reduced to 40% Tts (total transmission of solar energy) (60% rejected).
Solar Absorbing Glass is laminated or tempered, with a solar absorbing material to limit solar energy going into the vehicle. The total solar energy entering the vehicle is higher (55-60% Tts) than with Infrared reflective glass.
Compared to cars currently in showrooms, windows that comply with the standard will block 33% more heat-producing rays from the sun. This will cool the vehicle’s interior by approximately 14 °F for a car and 12 °F for a pickup or SUV. Lower temperatures require less use of air conditioning, both upon starting a car parked in the sun and while driving in sunny conditions.
Other benefits include a cooler interior upon entering the car, less time for the air conditioning to reach a comfortable temperature, and reduced fading of upholstery and cracking of the dashboard.
The regulation has two steps:
Over a three-year period starting in 2012 windows in new cars sold in California must prevent 45% of the sun’s total heat-producing energy from entering the car, with the windshield rejecting at least 50% of the sun’s energy.
In 2016 car manufacturers will be required to install windows in new cars sold in California that prevent at least 60% of the sun’s heat-producing rays from entering the cars interior, or propose alternative technologies to achieve an equivalent result.
Costs for the windows are expected to average $70 for the 2012 standard, and about $250 for the 2016 standard, with annual savings in gas of $16 and $20 respectively. Costs would be recouped over a five to twelve year period.
This initiative follows on the heels of a series of other measures adopted by the Board under AB 32 to reduce greenhouse gas emissions from vehicles. These include a standard for cleaner lower-carbon vehicle fuels, and a regulation to ensure tire pressure is checked at smog check, oil change and other maintenance facilities.
California is also awaiting approval of a waiver from the federal government to enforce standards under its Clean Car Law that will reduce greenhouse gas emissions 30% from vehicles over the next seven years.