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.



9 Responses to “CP Films Releases a Re-Calulation of the Solar Energy Spectrum”

  1. 1 Mike Feldman August 2, 2008 at 3:28 pm

    We are both too wisened and cynical to believe that 3M (and more recent copy cats will “cease and desist” in their spurious marketing claims concerning infrared rejection %.

    The LIE has long ago jumped out of the bag.

    The BTU test and IR meters are ubiquitous.
    Dealers claim their prestige fims out-perform silver 20 and darker. They advise consumers that their film works better when it’s hotter.

    I spell lies like this: L I E S .

    Thanks for sending out this warning flare to alert fair and ethical competitors that they have to be fluent in these matters so that they might hope to educate their prospective customers!

  2. 2 vclimber August 2, 2008 at 3:43 pm

    I’m just hoping that the article will get published somewhere more mainstream than just across their dealer network so that more people will have access to this information. WF Magazine would be a good start but it is a trade publication and not everyone subscribes to it.

    I will probably write a few more detailed observations when I can but it would be hard to do any kind of justice to the actual article complete with very informative graphs and so forth.


  3. 4 vclimber August 4, 2008 at 9:19 am

    Is CP ok with you publishing that link?

  4. 5 Film-r August 5, 2008 at 11:57 am

    Very good read. I noticed a TV commercial the other day. It was sponsored by the government, it mentioned getting the windows tinted in your home to save energy. I live in Ontario Canada, we have winters.. I was happy to see this ad thats for sure. This information is needed to be seen by the public. Perhaps one of you two could get CP to publish this in a HOME IMPROVEMENT or HOME AND GARDEN MAgazine..

    Good luck, keep up the great work!!!

  5. 6 windowfilmonline August 5, 2008 at 12:23 pm

    Appreciate your suggestion Film-r. I know that CP Films advertises their Vista Window Film line in several publications. As for publishing this particular article, I think that it would fly over the heads of most consumers which is not the best way to spend your marketing dollars but as vc said, the information needs to get out into the mainstream. All that we can do here is use this channel to bring the most up to date and accurate information that we can find to the public. I doubt that we could influence what CP Films or any other manufacture decides to do in this matter.


  6. 7 Leonard August 19, 2008 at 7:52 am

    Our industry try to advertise in Famous Sugar Water Style – “Our sugar water kill thurst” – tell they. We all know that NO. THURST WILL WIN. But we all buy! The difference is that window film sellers want to show specific scientific data’s to people who anycase understand nothing. And …yes, got result. That’s easy – to declare “Our films cut this one, this one and this one!” Just my 2 cl 🙂
    Sorry for my English and good lick to blog, really nice and so sad that my english is not so good to understand all that!

  7. 8 Steve Charlson September 28, 2008 at 9:32 am

    You all are close, but still far off. SHGC is as deceptive as what you decry – NFRC shgc rating procedures are selective source / selective measure, also.
    Lumens per watt and adjusted lumens per watt are the only objective lighting efficiency metrics. (Selkowitz, LBNL, 1984)

    Aluminum windows provide twice the lumens per watt as wood windows. (Selkowitz, 1984)

    White acrylic domes provide a minimum of 150 lumens per watt. (HMG for PIER, 1998)

    Low E windows with spectrally selective coatings are less efficient than candles and kerosene lamps. Test for yourself using the only objective, scientific metrics for rating lighting devices.

  8. 9 vclimber September 29, 2008 at 11:09 am

    Glad to have you on as a reader Steve.

    I think there may be a misunderstanding, perhaps you could explain the context in which you are applying LPW to window film performance.

    We use SHGC as a total performance measurement to compare the total performance of one window film to the next in its ability to regulate energy coming from the solar spectrum roughly between 330nm-2500nm. The SHGC helps us to see how much energy is transmitted through window film and the glass and can be used to model the performance of an entire window system. It is not being used to determine lighting or overall building performance which is a much more complex equation that involves many other factors besides the SHGC of the windows.

    Glass is the largest energy loser in a building’s envelope and while coatings such as low E can be used to reduce far IR loss, it is like you mentioned still very insignificant. There are window technologies that work very well and have achieved R values of up to R-20. However, in typical situations studies have shown that heat gain control is much more of an issue when it comes to windows than heat loss.


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