Window films have long been used for various purposes, such as solar control, privacy, and safety. However, one of the most attractive and sought-after functions of window film is its ability to save energy.
While most solar control window films offer some degree of energy savings, particularly during the winter, Low-E (low-emissivity) films are the optimal choice for improving window insulation properties year-round.
These films not only enhance heating efficiency during the winter but also provide cooling benefits during the summer.
Understanding Low-E: What Does It Mean?
The term "Low-E" refers to a window's emissivity, which measures the percentage of heat reflected back into a room versus how much radiant heat is lost to the outdoors. The lower the emissivity (or “e-value”), the better the film is at saving energy. Most solar control films have an emissivity of around 0.84 (or 84%). Low-E films, however, boast significantly lower e-values, making them far more effective for energy efficiency. These films reduce heat loss in winter and help prevent heat gain in summer, offering critical year-round energy savings.
While emissivity is an important factor in determining a Low-E film's performance, it's crucial to consider other aspects that contribute to overall efficacy. Not all manufacturers disclose the emissivity of their films, but this value alone shouldn't be the sole criterion for choosing a Low-E film. Below are some of the top Low-E window film brands, along with their emissivity values and other key features.
Top Low-E Window Film Brands
1. Enerlogic
Emissivity: 0.07 (7%)
Features: Enerlogic claims to have the lowest emissivity in the industry, promising the highest potential savings. Their patent-pending coating delivers energy efficiency in every season. Additionally, the film offers a spectacular appearance, enhancing both functionality and aesthetics.
2. Solar Gard: Silver AG
Emissivity: 0.22 (22%)
Features: Known for its low emissivity, Solar Gard Silver AG effectively prevents heat from escaping through windows in winter while providing high heat rejection in summer. This film is ideal for architectural purposes, offering incredible clarity and a fast return on investment (ROI) in dual-climate regions.
3. Llumar
Emissivity: 0.33 (33%)
Features: Llumar's Low-E film provides excellent energy conservation and robust solar control properties, protecting homes from 99% of ultraviolet rays. Its advanced solar technology reflects infrared heat while still allowing natural light to pass through, optimizing both energy efficiency and interior comfort.
What Is Low-E Film?
Low-E film, also known as sun or climate control window film, is a thin layer of plastic or metallic material applied to the inside of a window. It improves comfort, privacy, safety, and security while saving energy by blocking up to 99% of UV rays. This type of film is typically available only to professional installers in the United States, though alternatives like heat-rejection and UV protection films are available for DIY enthusiasts.
Cost and Installation of Low-E Film
In the United States, installing Low-E film costs between $4 and $19 per square foot for materials and labor. Although this may seem pricey, it is significantly more affordable than installing factory-made Low-E glass windows, which can cost between $40 and $55 per square foot. Low-E film offers a cost-effective solution for improving window energy efficiency, with potential savings on utility bills and reduced energy loss.
In countries like the United Kingdom, Low-E film can be a do-it-yourself project. However, in the U.S., these films are generally available only through professional installers, ensuring a high-quality application without bubbles or edges peeling up over time.
Considerations Before Installing Low-E Film
When considering Low-E film, it's important to assess your climate, window orientation, and existing window properties such as Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT). Low-E film is particularly effective in regions with extreme temperatures, helping reduce electric bills by maintaining a stable indoor environment.
Low-E film also offers additional benefits, such as reducing glare, increasing privacy, and protecting interior furnishings from UV damage. However, it may void the warranty on certain types of windows, particularly double-paned ones, by causing differential expansion between the interior and exterior panes.
Low-E Film vs. Window Insulation Film
It's essential to differentiate between Low-E film and window insulation film. While Low-E film enhances energy efficiency by reducing heat transfer through the glass, window insulation film is designed to reduce drafts by insulating the entire window frame. For homes experiencing drafts, window insulation film, caulking, or weather stripping are more appropriate solutions.
Conclusion
Low-E window films are a smart investment for homeowners looking to improve energy efficiency, comfort, and protection from UV rays. These films offer a lower-cost alternative to installing new energy-efficient windows, providing year-round savings and a more comfortable living environment. While there are considerations to keep in mind, such as potential warranty issues and installation requirements, the benefits of Low-E film make it a compelling option for any home.
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