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Volume 41,   Issue 2       February 2006


Keep it Together
    
Incorporating Window Film into Insulating Glass Units 

by Craig Duncan

he art of applying window film onto glass has been with us for many years and has grown into a multimillion-dollar business. Among the many desirable benefits that window films provide to the end user are increased privacy, ultraviolet light protection, solar heat rejection and impact resistance. While these benefits have been available to the aftermarket industry for many years, the past couple of years have seen these benefits introduced to OEM markets.

The transition of this technology took place through the development of an application process called dry lamination. Unlike the conventional methods of applying film, which involve water-based application solutions, dry lamination is done with specialized equipment in a clean room environment.

Benefits for IG Manufacturers 

Dry lamination is being used today by several companies to mass-produce dry-laminated impact windows. Many years of testing and engineering have resulted in a process that allows the useful properties of film to be incorporated into an insulating glass unit (IGU), while still meeting the demanding quality requirements of the fabricators.

The whole dry lamination process is designed to be added easily into a conventional IGU assembly line. The cleanroom and laminator are added after the glass washer. As glass exits the washer it immediately goes into a laminator that applies the film precisely. After the film is applied the fabricator can begin assembling the IGU or save the glass-film composite for later use.

Unlike traditional window films, films used in an IGU do not have any scratch-resistant coatings. They are designed to be laminated on the second and third surfaces of the unit, making a scratch-resistant coating unnecessary. This also eliminates any potential for out-gassing. 

The film forms an instant bond to the glass upon lamination and eliminates the need to wait for the film to cure. Retrofit films often require several weeks to several months for the application solution used to mount the film to fully evaporate. Until this curing is complete, any impact performance is minimal. With dry lamination, the bond occurs as soon as the film is laminated to the glass. 

Meeting the Needs

Impact performance is by far the biggest reason fabricators consider incorporating dry lamination into their process. The need for windows that protect people and houses during inclement weather has grown exponentially over the last few years. This has been fueled by the recent increased numbers and intensity of hurricanes hitting the United States.

In response to the damage these storms create, many states and counties have adopted stringent requirements for the impact performance of all windows installed in new constructions in costal counties. One way to meet the requirements is to dry laminate an impact-resistant window film composite into an IGU on the second and third surface. This combination has been proven through multiple independent certified testing labs to withstand the 2X4 impact test.

Unlike other methods of meeting these requirements, adding film to the IGU increases the weight of the window by only a small percentage. This weight reduction is the biggest reason that window fabricators are turning to dry lamination. Other methods can add tremendous weight to the window so that only partial shipments can be sent due to highway weight restrictions.

These lighter weight windows are easier to install. The sashes and counter can also be reduced since they do not have to support the additional weight of traditional laminated glass. All of these savings have driven the push to bring dry lamination technology to where it is today.

Aside from just impact performance, dry lamination also provides the fabricator with increased flexibility. By laminating film onto standard annealed glass, the performance properties of tempered glass can be obtained. This has been proven by certified ANSI Z97.1 and CPSC 1201 Cat II (unlimited) testing. 

Opportunities Abound

Fabricators arenít the only ones taking advantage of some of the new developments that dry lamination has brought fourth. Architects are discovering the array of possibilities that can be created when silver spandrel films, for example, are laminated onto different types of glass. By using different shades of silver spandrel with colored glass, architects are able to add color and texture to buildings that are different from anything seen before. These products also carry the ASTM C-1048 standard. 

The future for using films in IGUs has never been better. A recent Ducker research study estimated that 22-million square feet of hurricane-resistant impact products will be produced in 2007. Windows produced using film will make up a growing percentage of this number.

Whatís Next? 

Looking further into the future, the next big jump for window film will be in development of films that block almost all IR-waves without reducing the amount of visible light let in. This technology already exists, but it continues to improve as new materials are discovered and better methods are found for depositing these materials onto film.


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