I'm interested in solar window film and I'm not sure which product to use. Solar Guard film (with metals) or 3M Prestige (no metals)?
I live in NJ so I have to deal with both hot and cold climate issues.
Please first read the last article I wrote on the subject to gain a basic understanding about how films work and what alternatives there are: "I am trying to research, compare and decide the most energy efficient product for all my windows: solar screens vs. solar film?"
You need to be aware that while a window film may help with your heat issues in summer, it will certainly be bad in winter as it reduces any possible heat gain. That said, if you decide film is right for you, get one that reflects the energy rather than absorbs it. At least it will do the summer job right.
Metal films are usually better at reflecting, as colored films work more by absorbing heat. The 3M webpage does not differentiate their test data between reflected energy and absorbed energy, which leaves you in the dark about how the film really works. The Solargard product has clearly published test results so you can select the percentage of reflected energy you desire (third column, R%).
However I cannot stress enough that if you want to have a greener home and a great interior temperature you need to use something else than films that differentiates between summer and winter.
Overhangs do that best because the sun angles are different but are sometimes hard to retrofit. Consider a small trellis maybe, or a large one over your attached deck, that you can cover with a shade fabric in summer. Or get exterior shades installed.
You will be much happier in the long run, although the upfront costs are higher.
For more information:
Read Andrea Foss's answer to the question "We're considering having a window film applied as a low-cost way to save energy. How effective is this?"