Car cabin cooling tricks lower interior temperature by up to 10 °C

Two recent studies investigated how to cool a parked car quickly. A Stanford experiment found that repeatedly opening and closing the driver’s door while the window is slightly lowered creates a low‑pressure zone that expels hot air, dropping cabin temperature by up to 3.6 °C per minute. After this “Japanese method” the car, driven with the air‑conditioning on, reached a comfortable 30 °C within 20 minutes.

The German auto club ADAC tested seven identical Dacia Dusters under strong sun. Covering the vehicle with a tarp reduced the driver‑seat temperature by about 10 °C, making it the most effective shield. A protective film lowered the temperature by 8 °C, while tinted rear windows saved only 2 °C. Light‑colored cars stayed 20 °C cooler inside than dark ones.

Both studies suggest simple, low‑cost measures—window‑flapping, external covers, and lighter paint—can substantially mitigate the greenhouse‑effect inside vehicles on hot days.