Archive for August, 2008



CP Films Releases a Re-Calulation of the Solar Energy Spectrum

If you do not have CP Films’ July 2008 Technical Updates Newsletter then you had better figure out how to get your hands on a copy. The article features and in-depth look at false and misleading claims about infrared transmission and rejection. Sound scientifically based reasoning is used to help readers understand what these numbers “mean and DO NOT mean” and the value and accuracy of using infrared measurements is reasoned upon very well. The most notorious infrared rejection claim in our industry is challenged and exposed so thoroughly as erroneous, inaccurate, manufactured, and misleading that it leaves one to reconsider whether they should even be using such information to sell and market window film. The accuracy of IR lamp demonstrations and measurement readings by common metering devices is put into question because of the selective broadcasting of energy by an IR lamp and the selective measuring of that energy by a metering device not to mention the possible calibration issues. A call to cease and desist these claims was made in order to preserve the good reputation of our industry and a recommendation to use the TSER and SHGC values to asses the true solar performance of films was issued once again. Hopefully, this call to action does not fall on deaf ears.

Most noteworthy to me was the re-calculations of the solar spectrum. Traditionally, our industry has always published the belief that 44% of the sun’s energy is from Visible Light, 3% from UV, and 53% from Infrared regions of the solar spectrum. Making good use of their $80,000.00+ spectrophotometer, LBNL’s Window 5.0, good mathematics and physics, CP Films’ Technical Services was able to recalculate the energy distribution and discover that the energy content of solar UV is 1.81%, Visible is 49.26%, and IR is 48.93%. “No one ever bothered to check the facts”, they say!

The newly recalculated energy distribution across the solar spectrum.

The newly recalculated energy distribution across the solar spectrum.

The article states that these calculations were “made in good faith” and that independent corroboration is welcome. I would urge any companies with the capacity to verify this information to do so for it changes not only our understanding of energy distribution but more importantly, the way we should specify, design, rate, and advertise the performance of window films. It underscores the importance using of total performance measurements like TSER and SHGC to asses the true solar performance of window films rather than regional measurements such as IR rejection or transmission. It will also change the way that manufactures market their products to window film dealers and hopefully it will change the way dealers are trained to sell window film to the general public.

Lastly, whether you love them or hate them there is no denying the incredible contribution that CP Films has made to our industry. This article is another good example of that fact. The need for total solar performance measurements that are accurately verified by independent third party organizations has become clear, and a foundation for a movement to window film certification by the NFRC has been well-layed. If our industry is to gain and maintain any kind of credibility with various organizations and the general public we need studies like this one to help us all see that accurate and relevant data is essential to the marketing and sales of window film.

-vc

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