We're considering having a window film applied as a low-cost way to save energy. How effective is this?
We live in Annapolis, Maryland. Most of our windows are south and east-facing. I think they are low-e, but I am not positive.
If your windows are already low-e, then adding an additional film is not going to make that much of a difference. You can tell if they are low-e by taking a piece of white paper outside and looking at the reflection in the windows. If it looks white, then it's not low-e. If the reflection looks yellow or pink, it is most likely a low-e window.
By and large, messing with your windows will not significantly lower your energy bills. Improving your insulation, air sealing, and HVAC will give you the biggest bang for your buck.
That being said, the only way to truly know the most effective steps to save on your home's energy costs is to get a home energy audit.
The Maryland Energy Administration maintains a list of certified energy auditors and retrofit contractors at mdhomeperformance.org.
For more information:
Find an energy auditor in GreenHomeGuide's nationwide directory of green professionals.