For modeling window films, you first have to determine what´s the effect in the U value and Solar Heat Gain Coefficient. LBNL Window allows you to do U value and SHGC calculations for different Insulated Glass Assemblies, but does not have the built-in capability of modeling window films.
I suggest that you become familiar with LBNL Optics software. Here´s the link https://windows.lbl.gov/software/opti.... Download the software, read the manual, and make some testing for yourself. Optics has glass and films libraries and allows you to build assemblies with them. After you make a glass/film assembly in LBNL Optics you can then import it within LBNL WINDOW to model either single, double, or triple glass assemblies. In Energyplus you enter the data for either a simplified or complex fenestration object, but you need to enter accurate data that was either previously calculated or from a product manufacturer.
I hope this is useful for you. Best Regards.
Stop thinking about E+. First, think about what window films do. What property of your window do they affect? Then you should be able to answer your own question.
My interest in modeling it instead of defining an overall U value is due to the fact that my thesis is addressed to the software itself to which I must explain which objects I added or modified in order to accomplish the retrofit measures I suggest. Only if there's no way of directly modeling something in particular I may change the properties of the existing materials to simulate it.