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Retrofit Low-E Window Films
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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

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

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:

Q&A: Low-e Retrofit Products - Window Films - PDF version; use your browser's back button to return to this page. Original article, Solar Age Magazine, September 1986, adapted and updated for InspectAPedia.com in 2011.
Q&A: Low-e Retrofit Products - Window Films-page2 - PDF version; use your browser's back button to return to this page. Original article, Solar Age Magazine, September 1986, adapted and updated for InspectAPedia.com in 2011.

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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  LOW-E WINDOW GLAZING
  LOW-E VS QUAD-GLAZING
  LOW-E RETROFIT ADD-ON FILMS

Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
3M Corporation, 3M Energy Control Products Project, Building 224-5S, St. Paul MN 55144 [1980's]
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the InspectAPedia Bookstore
"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
"Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
"Heat Exchangers for Solar Water Heating Systems", U.S. DOE describes the types of solar water heater heat exchange methods between the sun and the building's hot water supply
"Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
"Solar Water Heating System Maintenance and Repair", U.S. DOE
"Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
"Scaling and Corrosion in Solar Water Heating Systems", U.S. DOE
www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these articles
"Active Solar Heating Systems", U.S. Department of Energy, including
"Radiant Heating Systems" U.S. DOE
"Absorption Heat Pumps & Coolers", U.S. DOE
"Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building
"Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.

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Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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Comparing Energy Efficiency of Low-E Glass vs Quad Glazing

Low-e Window Retrofit Film Products

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

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

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair