Hi, car cabin temperature will definitely increase if you park your car in open space for more than an hour. This is due to the heat being slowly accumulated over time, but cabin temperature will cool off fast once you turn on your air-cond if you are using a high irr film like Ultra70 The main function of the film is to reduce the heat while you are driving so that you can enjoy a comfortable ride. However, there is a solution for reducing the temperature after parking the car, which is to install a very dark film to block the light from going into the car at all, but we all know that this is not comply to JPJ regulations