Window film is the poor man’s version of energy efficient windows. It’s often called heat control window film, and it acts much like this expensive low-E coating that the window companies are always trying to shove down your throat. Except this is a whole lot cheaper.
Window film isn’t bad stuff at all. But applying window film is a bitch. Have you ever seen some idiot who has self-installed window film on his car? Seen those bubbles and creases? Well, that’s the kind of thing that may happen when applying window film on your house’s windows.
The only saving grace is that your house’s windows are flat. The idiot’s car windows are curved, which makes the install much harder. And makes him less of an idiot than previously thought.
Trying to get two pieces of window film to meet side by side is nearly impossible. You’ve got enough problems trying to get the film to meet up with the glass’ perimeter, much less trying to mate up two pieces of window film in the middle.
But the easy way to do this is to simply overlap the two pieces of window film. Then use a straight edge (i.e., your metal ruler) and X-Acto knife or very sharp utility and cut right down the middle of the overlap. Then you can easily remove the two waste pieces of window film. Voila—two pieces of window film that meet up perfectly.