I am trying to sift through sales propaganda to see if this window film would be economical for me. This film is in contact with the window and blocks light energy from passing. In the summer, radiant heat from outside is cut down and the house is kept cool. In the winter, heat is kept in the house because it is not allowed to radiate out.
This seems like they're not telling the whole story. Sunlight radiates in during the winter as well and I think this is greater than the heat radiating out.
So cooling costs in the summer would be lower, while heating costs in the winter would actually be a little higher. The reason I think this might not be economical is that I have no air conditioner in the summer and I heat my home with electric heaters in the winter.
Is my reasoning correct?