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Retrofit Low-E Window Films

  • Compare Energy Efficiency of Low-E Glass vs Quad Glazing
  • Add-on films for low-e energy-efficient window glazing
  • Low-e window films for upgrading existing windows
  • Winter films and all-weather films retain indoor heat in cold weather
  • Low-e coated films for inside storm windows
    Questions & answers about using add-on or retrofit films to improve window energy efficiency
  • Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
  • POST a QUESTION or READ FAQs about low-E window films

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Adding low-Emissivity film coatings to windows: this article describes low-e window films that can be added to existing windows to improve window efficiency and improve solar gain in cold weather.

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Comparing Energy Efficiency of Low-E Glass vs Quad Glazing

The text below is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Readers should also see SUNGAIN, FILMS, LOW-E GLASS for details about use of Sungain film on windows and window film selection and installation, and see WINDOWS & DOORS our home page for window and door information. A wide range of energy conservation and solar energy topics is found at SOLAR ENERGY SYSTEMS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Low-e Window Retrofit Film Products

Question: are there any low-e coated products for window retrofits?

Are there any low-e coated products available for retrofitting existing windows? - Ed Swiderski, Pawtuckett RI

Answer: Yes several low-e window films and an inside storm window

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Two low-e window films and one inside storm window were available in the mid 1980's and more such products are currently provided by several manufacturers.

The add-on or "retrofit" low-e window films are applied to the inside of the window glass with a squeegee, using water as the adhesive. These "winter films" or "all-weather" films are tuned to retain winter heat and reject some outside heat gain.

They probably make the most sense as window energy improving retrofits in houses located north of the Mason-Dixon line.

Scotch-tint Plus All Season claims to reduce heat gain by 60 percent and wintertime heat loss through the window by 40 percent. it also blocks 98 percent of UV light that fades indoor furnishings. Scotch-tint is available from 3-M Co., St. Paul MN.

The second low-e retrofit window film is Gila River Products' [Chandler AZ] PWD-5 with roughly similar characteristics to the 3-M Scotch-tint film.

With a winter U-value of .85, this film ups the R-value of a single pane 1/8-inch thick window [glass] from around .90 to 1.18, a 31 percent improvement in window efficiency.

What is lost when a low-e film like these is applied to a window is some useful solar gain and light in winter, due to the film's low transmittance (0.55).

To our knowledge, the only low-e retrofit storm window is the Windo-Tite unit. It is an aluminum-framed single window that attaches to the inside of the primary window via swivel clips or sash locks. It has a tested U-value of .408 (r-2.45 for storm plus primary window). Amesbury Industries, [Amesbury MA] supplies the glazing frames and accessories to local distributors who make up the window units.

For more up to date information about the performance of films to increase solar collector efficiency, see SOLAR COLLECTOR FILMS

As we discuss in more detail at SUNGAIN, FILMS, LOW-E GLASS, here is a quick comparison of window types and their efficiencies:

The question-and-answer article above paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

This article is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.


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