Advanced lightweight insulation and window technologies can contribute significantly to achieving industry and government goals of substantially improving fuel economy without loss of vehicle performance or passenger comfort. Two conventional passenger automobiles, a 2001 sport-utility vehicle (SUV) and a 1999 mid-size sedan, were retrofitted with lightweight insulation; the sedan was also fitted with specially designed windows. The body insulation and windows reduce heating and cooling loads, which allows downsizing of heating, ventilation, and air conditioning (HVAC) equipment. Benefits derived from the use of advanced insulation and window technologies include: Demonstrated reductions in cooling loads; Fuel savings for conventional and hybrid vehicles; Extended range for electric vehicles; Greatly improved passenger comfort; Reduced degradation of interior surfaces; and Improved safety. The research vehicles were retrofitted with Lawrence Berkeley National Laboratory's (LBNL) patented gas-filled panel (GFP) insulation. GFPs are multi-layer baffle constructions made from lightweight films and filled with a low-conductivity gas. These lightweight panels can be up to three times as effective as conventional foam insulations depending on the type of gas used. The GFPs used in the automobile retrofits had a krypton or xenon gas fill, which provides an effective thermal resistance of R-12 per inch and R-20 per inch, respectively. By comparison, expanded polystyrene has a thermal resistance of R-5 per inch.The solar-control glazings used in the sedan retrofit consist of special coatings, which create a narrow-band-pass filter that rejects ultra-violet and infrared (IR) wavelengths. The result is much less heat gain into the interior of the car and less degradation of interior surfaces. The retrofitted cars were tested under driving conditions in a wind tunnel and in an outdoor setting. Test results show that vehicle warm up under soak conditions (vehicle parked in the sun) was delayed compared to a factory vehicle.