True, under certain circumstances. Standard sun control films that only impact a window’s SHGC will reduce the amount of visible light entering a building. That visible light is typically used to help heat the building in the winter. Therefore, heating costs may rise. However, insulating window films that not only reduce a window’s SHGC but also its U value help to reduce winter heat loss. Consequently, those films provide savings year round and should not cause heating costs to rise.