Recently the California Energy Commission (CEC) put window film on the fast track to get it into the new building code—to be effective in 2014. As the first state in the nation to place window film in the next building code, California has officially recognized window film as a legitimate, cost-effective energy saver.

This change in thinking is due to recent reports and studies that show just how effective window film, a thin polymer adhered to the inside of glass, is. One such study is the “Energy Analysis for Window Films Applications in New and Existing Homes and Offices,” which was completed by the International Window Film Association (IWFA) and Consol Energy Solutions. (IWFA is a nonprofit industry body that facilitates the growth of the industry by providing unbiased research, influencing policy and promoting awareness of window film.) Their research used similar processes that are also used by the California Energy Commission to analyze alternative measures for energy-savings.

The home modeled in their study was a 2,123 ft2, two-story, single family detached unit, representative of the new construction housing in California. One finding of the study was that for existing homes with single pane glass, window film can have more impact than putting R-38 ceiling insulation in an attic.  

Intrigued by the study and its results, we decided to speak with Darrell Smith, executive director of IWFA.

Q&A with Darrell Smith, IWFA

Home Energy: Can you give me some background on the study you completed?

Darrell Smith: ConSol was contracted to help the IWFA ascertain the steps needed to be taken for window film to be included in a California “retrofit” code being developed for the future. One of the obstacles they found was that window film use had not been analyzed using the same specific software and methodology which the California Energy Commission uses to assess different energy saving measures. ConSol was then asked to perform such an analysis both for residential and commercial buildings. The study did not require physical testing of any windows; instead, it utilized required software programs for the analysis.

HE: Why do you think it's taken so long for window film to be a recognized energy saving measure? 

DS: Although many persons, both inside and external to the window film industry, knew energy control window film was a great retrofit option to save energy, most evidence was either “anecdotal” or applied only to a single installation. Only after the National Fenestration Rating Council (NFRC), working with representatives and manufacturer members of the IWFA, established a method for certifying and labeling the energy performance specifications of window film as installed on a window did the industry have credible third-party certification of its claims of energy performance.

HE: How has window film evolved over the years - both physically and in price (if it has)?

DS: The product offerings have moved from just colored (tinted) products or very reflective (shiny) products to a full line of products which can be ranked for its glare control, UV protection, decorative ability, safety or security enhancement, and degree of energy control-both solar energy and room heat retention.  Today’s technology allows a homeowner to prioritize his/her needs and then simply select from a multitude of products which best meet those needs at the value level acceptable to the consumer.

HE: What do you think readers of Home Energy would be most surprised to learn about window film? 

DS: That the darker or shinier window films of the past offer no more energy control than many of the almost “clear” films of today.

HE: What is the most common misconception of window film? 

DS: That it is the dark or bubbly product either from a very old installation or installed improperly by a lay person rather than a trained installation expert.  Modern window films are warranted by the film manufacturer for periods of 10 or 20 years, dependent on type of film chosen and its end use, and many of the newest products have limited lifetime warranties. So today’s window film is a long-lasting building material especially designed for retrofit to an existing window.

HE: Are there certain geographic areas that benefit more, or less, from window film installation? 

DS: In the past, energy control films were primarily only solar control films—that is, they controlled the sun’s energy coming through a window. Therefore the best use of those products was in areas where the length and energy cost of the “cooling season” (need for air conditioning) was greater than that of the “heating season.” Many of the new window film products today also are “low-e” type products and can offer added energy savings during the heating season.

For more information on the IWFA and window film, visit their website.

To download the entire study completed by IWFA and Consol, click here.

This blog originally appeared at HomeEnergy.org.

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