The correct film will not cause your windows to break. Not all films can be used on all glass types however. Manufacturers have guidelines that need to be followed to ensure the glass will not break because of the film. There are some instances (about 1 in 750) where after the film is installed, glass breakage does occur. This is typically attributed to weak or defective glass that is hidden by the frame. In the event of breakage there is warranty coverage for the glass and the window will be re-filmed at no cost to the consumer.