Are Moving Glass Walls Energy Efficient?
Creating a seamless indoor-outdoor living environment with moving glass walls can transform the way you live. A greater connection with nature, expanded space, and improved access to natural light, ventilation, and views are just a few of the main benefits associated with sliding and folding glass doors.
But when temperatures begin to rise and fall and the doors are closed, how do these moving glass wall systems keep interiors comfortable? More importantly, how will they affect heating or cooling costs? An assumption might be that sliding and folding glass doors offer less of a barrier between the interior and exterior, and therefore less protection from the outside elements. In the past this may have been the case, but advances in glass technology, materials, premium manufacturing, and energy certifications have changed the game.
Understanding each of these components will help you understand why insulated moving glass walls are a worthwhile investment that can sustain comfortable interiors while decreasing energy costs over time.
Getting the Gist of Glazing Options
In general, there are three terms when speaking about glazing (the layers of glass in a moving glass wall): single-glazed, which refers to one pane of glass; double-glazed, which refers to two panes; and triple-glazed, which refers to three panes. The more panes of glass, the more energy efficient the sliding or folding patio door will be.
In addition, the space between the glass panes can be filled with gas to further improve energy efficiency. The most commonly used gas is argon, a non-toxic gas that is six times denser than air, offering better thermal protection. Argon-filled, dual-pane glass prevents temperature loss to the outside while reflecting it back into a room. This helps to reduce heating and cooling costs.
The glazing can also be treated with coatings and films to improve energy efficiency. Glass with special Low Emissivity (Low-E) coating on the surface may allow up to 20 percent less solar heat to the interior, compared to a double-glazed window of similar area with standard glass.*
How does this work? Low-E glass has a transparent, thin coating that reflects heat. When the heat on the interior of the home tries to escape to the colder outside during the winter, the coating reflects the heat back to the inside. The opposite occurs during the summer, keeping it cool inside.
At Skye Walls, we use Low-E3 argon-filled dual pane glass, one of the highest performing glass packages, as our standard option.
Why Frame Materials Matter
Sliding and folding glass door frames can be manufactured from a variety of different materials, including fiberglass, vinyl, wood, and aluminum. Each material differs in terms of strength, durability, cost, aesthetics, maintenance requirements, and the level of insulation it can provide. Skye Walls uses both aluminum and vinyl frames to optimize long-term performance with a premium look and feel.
Aluminum: In addition to being a known heat and cold conductor, aluminum is a durable material that requires very little maintenance. Traditionally, aluminum has been considered less energy efficient than fiberglass, vinyl, or wood – but technological advancements have changed how aluminum conducts heat and cold. To ensure thermal performance in all kinds of climates, Skye Walls uses thermally broken aluminum frames that incorporate insulation into its aluminum sliding and folding glass door systems, “breaking” the path of conduction.
Vinyl: Vinyl frames may lack the strength benefits of aluminum, but are low-maintenance, cost-effective, and generally energy efficient. Details of the door’s construction, such as welding and internal structure, can greatly impact how energy efficient it is.
The Importance of Energy Performance Certifications
There are a few ratings, certifications, and codes to consider when selecting an energy efficient sliding glass door. These codes may vary by region. Fortunately, organizations like the National Fenestration Rating Council (NFRC) independently test and certify multiple measures of energy efficiency that can help when comparing options.
U-Value or U-Factor: The U-Value measurement rates how a product keeps heat from escaping a home or building. The lower the number, the better job it does of keeping heat inside, where you want it. The range is from 0.20- 1.20. This is a valuable measure for cooler climates and seasons, where keeping your home heated efficiently is a high priority.
Solar Heat Gain Coefficient (SHGC): SHGC is the measure of how well a product does at keeping out unwanted heat due to sunlight. Lower numbers indicate better efficiency, with a range from 0-1. SHGC is an important rating for hot, sunny climates, where keeping the heat out helps lower cooling costs.
Other terms you may come across when researching energy efficiency include Energy Star and California’s Title 24. Both look at how the NFRC ratings may be applied to reach specific standards.
ENERGY STAR certification: ENERGY STAR is a nationally recognized symbol for energy efficiency. ENERGY STAR certified products like glass doors and windows must be manufactured by an ENERGY STAR partner and be independently tested, certified, and verified by the NFRC. ENERGY STAR criteria can be different depending on the area of the country.
California’s Title 24: Part of the California Code of Regulations, Title 24 addresses energy efficiency in residential and non-residential buildings. Applying to new builds and some remodels, it requires an energy report to verify the building meets efficiency requirements as part of the permitting process.
Moving glass walls from Skye Walls undergo rigorous energy performance testing before getting certified by the NFRC and the American Architectural Manufacturers Association (AAMA). All are engineered to comply with California’s Title 24 requirements and many feature ENERGY STAR-qualified options.
A Worthy Investment
Whether you’re experiencing a heat wave or just a chill in the air, Skye Walls has a moving glass wall that can meet the energy demands of your environment. Designed to perform year-over-year, a Skye Walls sliding or folding glass wall incorporates precision engineering, material enhancements, and rigorous testing to ensure the least amount of heat and cold transfer while allowing for a broad array of sizes, configurations, and design aesthetics. This means less work for your air conditioner or heater which, in turn, helps to maintain a cozy interior and lower energy costs in the long run. Best of all, you get the added wellness benefits of an indoor-outdoor lifestyle.
*From the Consumer’s Guide to Buying Energy-Efficient Windows and Doors.