Why does the film feel warm on hot days?
All films feel very warm, even hot, when the windows are hot. The reason why depends upon the type of film, the type of window, and the type of weather. Basically, all films obstruct the transfer of heat from the outside of the window through to the inside of the room. The heat has to work much harder to move through this obstacle, so a lot of energy is dissipated through reflection, absorption, conduction, and convection. When you put your hand on the film, you feel much of this heat energy. Reflection measures how much energy the material reflects back into the glass. The higher the reflection, the greater the “heat gain” reduction. Utility companies often measure this as “shading coefficient.” Convection measures how much energy is drawn away. The main cause of convection is air movement, such as a breeze outside or a moving fan indoors. Convection helps cool a surface by pulling heat away. Absorption measures how much heat the material absorbs. For example, the Glare Control vinyl
