California mandates use of IR reflective auto glass

How infrared reflective film can help manufacturers satisfy demand
By Matt Coda
September 11, 2009
AUTO

In June 2009, the California Air Resources Board voted to enact the Cool Car Standards and Test Procedures, an early action item under California Assembly Bill 32’s greenhouse gas emission reduction directive. This action mandates auto manufacturers to improve fuel efficiency and reduce greenhouse emissions by using infrared (IR) reflective glass in all vehicles sold in California by model year 2014. The new regulations will be phased-in beginning in 2012 and apply to cars and all medium-duty vehicles weighing up to 10,000 pounds.

According to the U.S. Department of Energy, some 230 million vehicles in the U.S. consume 7 billion gallons of gas annually to power air conditioning. By reflecting the sun’s heat and maintaining a cooler cabin temperature, IR reflective glass reduces AC power consumption up to 20 percent and increases miles-per-gallon by up to 5 percent while lowering emissions.

In a parked vehicle, the solar energy transmitted through windows represents 50 percent to 75 percent of the thermal energy entering the passenger compartment and absorbed by interior mass. IR reflective glass used in DOE-tested vehicles reduced the cabin and seat temperatures by 34 percent and 35 percent, respectively, reducing the AC usage required to reach a comfortable temperature. In a moving vehicle, IR reflective glass maintained a lower cabin temperature, similarly reducing the need for AC.

AC load reduction can decrease fuel consumption because AC systems are designed for maximum cooling capacity, not efficiency. Testing a Cadillac STS, DOE determined that by using IR reflective glass, solar-reflective paint and solar-powered ventilation, the vehicle’s AC cooling capacity of 5.7 kW could be reduced by 30 percent to 4.0 kW while maintaining the same cool-down performance of 30 minutes. Simulation showed that reducing the AC load by 30 percent also decreased AC fuel consumption by 26 percent.

Making IR reflective glass and downsized AC systems standard for all vehicle models justifies the cost premium of the glass and makes it a value-added feature with increased margin potential for car makers. IR reflective glass and smaller AC systems can benefit large trucks and buses as well.

Although the new glass is mandated only for cars sold in California, automakers might eventually decide to adopt the technology nationwide as part of a comprehensive program to meet President Obama’s federal fuel-efficiency standards. Nonetheless, in a relatively short time auto glass manufacturers will have to ramp production of IR reflective glass to satisfy new demand by auto makers. In doing so, there are two basic approaches for making automotive glass IR reflective.

The first requires the glass manufacturer to coat an IR reflective layer directly onto the glass. This process, called direct sputter coating, involves processing glass through a vacuum deposition chamber, which creates high-density plasma of various heat-reflective metals. Atoms are deposited on the glass in thin transparent layers 5 to 30 nanometers thick, or about 1/10,000 of the diameter of a human hair.

The second approach involves Southwall Technologies' XIR film consisting of an IR reflective coating that is sputtered onto a clear polyethylene terephthalate film, eliminating the need to coat glass. This XIR coated film, which consists of transparent layers of indium and tin oxides and noble metals, is available off-the-shelf to automotive glass manufacturers that can laminate it with standard, uncoated glass to create high-performance and cost-effective IR reflective glass for original equipment manufactured and aftermarket products. 

Because IR reflective film is laminated into uncoated glass to meet a range of heat-rejection and visibility transmission standards, any automotive glass manufacturer can produce IR reflective glass without the need for expensive glass coating equipment. This “coater-in-a box” solution can dramatically accelerate the adoption of IR reflective glass by making it cost-effective for high volume models and low-to-mid volume model production, and for aftermarket replacement glass that otherwise could never justify the fixed costs associated with glass coating production. It also offers auto glass manufacturers better standardization of final product performance among a variety of manufacturing sites.

IR reflective glass incorporating XIR film technology is already being used in more than 20 million cars in Europe. Since 1993, XIR has been an OEM option offered by Audi, BMW, Ford (Europe), Land Rover, Maserati, Mercedes, Peugeot, Renault, Rolls Royce, Volkswagen, Volvo and others. Given its dependability, reliability and availability, IR reflective film will play a major role in the manufacturing of IR reflective vehicle glass in the U.S. and elsewhere.

Matt Coda is director, Automotive Business Development, for Southwall Technologies, Inc., Palo Alto, Calif. Write him at mcoda@southwall.com