Historically, while replacing large portions of the insulated building envelope with glass hurt overall efficiency, modern innovations in glazing and components mean leading sliding and bi-folding glass panel systems offer exceptional thermal performance. These modern systems use thermally broken frames and 1-inch insulating glass units which, together, can produce U-factors as low as 0.36. This effectively reduces dependency on air conditioning systems, improving the energy efficiency of single-family homes. To maintain a target of sustainable design, when architects specify demountable movable wall systems, whether sliding or bi-folding doors, specifying thermally enhanced units effectively mitigates heat transfer. Reducing heat transfer helps to keep interior temperatures cool during the summer and warm during the winter. This places less strain on HVAC systems throughout the year, which reduces energy consumption, and enhances comfort for occupants.

Movable glass panels also capture the twin benefits of daylighting and ventilation. Daylighting is the use of windows, doors, and skylights to bring sunlight into a home. Today's highly energy-efficient windows and doors can reduce the need for artificial lighting during daylight hours without causing heating or cooling problems. Not only does daylighting offset energy usage, it also aids occupant health. Relying on natural sunlight balances circadian rhythms and promotes better health and activity levels for those within the home. With documented research dating back to 1986, daylighting also has consistently been associated with improved mood, enhanced morale, less fatigue, and reduced eyestrain.²³ Bright lighting enables enhanced focus and alertness, and well-daylit spaces are generally perceived by occupants to be “better" than dim, gloomy ones.²⁴ Using glass allows people to enjoy distant, diverse, and dynamic views from the interior and establishes a link to the surrounding environment which fosters connection and creativity.²⁵

A home’s climate and design dictate the best way to incorporate daylighting. The sizes and locations of door systems and windows should be based on the cardinal directions, rather than their effect on the street-side appearance of the house. According to the U.S. Department of Energy (DOE), south-facing windows typically allow most winter sunlight into the home, but little direct sun during the summer, especially when properly shaded. North-facing windows admit relatively even, natural light, producing little glare and almost no unwanted summer heat gain. East- and west-facing windows can provide good daylight penetration in the morning and evening, respectively, but may cause glare, can admit a lot of heat during the summer, and contribute little to solar heating during the winter.²⁶

With an increased awareness of the cost and environmental impacts of energy use, natural ventilation has also become an increasingly attractive method for reducing energy use and cost and for providing acceptable indoor environmental quality. Large movable glass panel door systems are the star in any natural ventilation design. Natural ventilation, unlike fan-forced ventilation, uses the natural force of wind to deliver fresh air into buildings. Outdoor air is required in buildings to alleviate odors, provide fresh oxygen for respiration, and increase comfort. For the homeowner, bringing in fresh air maintains a healthy, comfortable, and productive indoor climate rather than relying on forced ventilation from A/C systems. According to the Whole Building Design Guide, in favorable climates and building types, natural ventilation can be used as an alternative to air-conditioning, saving 10%–30% of total energy consumption.²⁷ The amount of ventilation will depend critically on the size and placement of openings in the building, according to Andy Walker of the National Renewable Energy Laboratory.²⁸ An open floor plan and openings between rooms such as transom windows, louvers, and grills, are techniques to complete the airflow circuit through a building.

Providing Material Safety and Hardiness

Not only are high-performance products increasingly important to the savvy homebuyer, but avoiding chemicals of concern is also a growing focus. Environmentally preferable products that can provide durability equal a win-win for the design team and prospective owner.

There are many different types of pressure-treated wood available in today’s retail lumber yards. Treated lumber is no longer confined to suspicious shades of green with murky chemical labels. Leading manufacturers offer color-treated lumber products using an innovative micronized copper solution. MCA, or Micronized Copper Azole, is an effective and reliable protectant against rot, fungal decay, and termites in above-ground and ground-contact applications. Developed over years from intensive research, the MCA formula is subjected to ongoing, rigorous testing in thousands of test stakes at industry-recognized field test site locations all over the world. The finished product contains two active ingredients to stop decay and termite attack: copper and tebuconazole. Azoles are used in personal care products, such as foot creams and fungal ointments. Copper is a common metal used to build water pipes and electrical conduits, with which humans have contact every day. In MCA-treated wood, these two ingredients are applied in a mixture of water at a solution strength of less than 1% active ingredients (99% or more water). To produce the desired color during the process, the color is infused by driving pigment deep into the wood fibers.

While color-treated lumber is a new product within the market, its manufacturers stand behind the process. Horizontal applications boast a 2-year color assurance warranty; vertical applications feature a 5-year color assurance. Additionally, color-treated lumber with MCA has been independently verified as an eligible product for use in achieving points toward project certification under the ICC-700 National Green Building Standard.

The resultant treated product provides pressure-treated wood that is both an eco-friendly product and serviceable for decades. The EPA has registered the preservative process and deemed it appropriate for the protection of wood from rot and termites when used as directed. This simple formulation helps maintain the natural beauty of the wood while enhancing durability and maintenance. Color-treated lumber is also compatible with aluminum building materials, as it is less corrosive to fasteners.

Partnering for Good

Ultimately, a simple sale is not the final goal. Success in a residential project also means reduced warranty issues and call-back issues for the builder. The relationship between the design team and the builder is a true partnership, as the designer must specify materials and features to complement the builder’s goals. Acting as an important bridge between builder and architect is the manufacturer. Leading manufacturers fill a valuable role by offering trusted support, customization, and documentation to help inform the architect and provide service to the builder.

Maximizing Lifespan, Minimizing Maintenance

Guidance from a manufacturer that reaches beyond installation is critical to maximize the life of any product. For example, to forestall the impacts of the sun’s ultraviolet (UV) rays and the wet-dry cycle on color treated lumber, following routine maintenance has the biggest impact for providing long-lasting performance.

Color treated products using MCA, offer real protection from the sun’s ultraviolet (UV) rays. UV exposure is less damaging to these products than to untreated wood. Also, products containing built-in water repellent are better able to handle exposure over the first year or two. However, the more protection provided to the product, the better the long-term appearance and performance of the wood project. Therefore, re-application of a good penetrating product every year or two, particularly in demanding applications, helps keep an outdoor structure looking good for many years. High-quality penetrating products that boast water repellency and UV protection, are recommended for maintenance and should be applied to dry wood. These may be brushed or sprayed on.

Innovations that Last

Architects, quick to embrace the beauty and benefits of multiple glass panel door systems in residential settings, found themselves initially limited by size, color, or profile options. However, the latest innovations in sliding and bi-folding multiple panel systems feature a sophisticated design that makes a visual statement on a large scale, capturing the most desirable features in aesthetics and performance. For sliding systems, ultra-slim 1-5/16-inch panel rails and stiles create a minimal and uniform frame that produces uninterrupted views, while letting daylight flow freely to enliven interiors. With a maximum system height of 13 feet and panel width of 7 feet, sliding systems deliver expansive scale and elegance. Despite the large sliding panels, advances in hardware and components provide effortless operation. Panel loads are evenly distributed across the bottom rolling components resulting in a fluid, frictionless glide. A precision-engineered stainless-steel track further facilitates panel movement. Door automation is also available for hands-free operation.

Bi-folding door systems have also innovated and evolved. Distinctly slim 4-3/4-inch vertical posts and 1-7/16-inch rails reduce visible hardware and produce clean sightlines that maximize views. Panel hinges are completely concealed to deliver a minimal, streamlined look. Leading manufacturers offer superior thermal and structural performance using thermally broken framing and 1-inch insulating glass.

For sliding and bi-folding systems, those distinguished by a NAFS CW Performance Class rating are ideal for exterior applications where larger sizes, higher load requirements, limits on deflection, and heavy use are expected.

Leading manufacturers also stand behind the hardware of movable glass panel systems. Multipoint locking mechanisms, integrated stainless steel flat handles, track options, and testing of components to 40,000 cycles and beyond indicate a product that can be chosen with confidence. Color options are also expanding, with Matte Black, Bronze Anodized, Satin Anodized, Black Powder Coat, and White Powder Coat Glossed as standard.

Though the residential market faces challenges, new products are allowing home construction to capture resilience and durability. By placing high-performance design first, today's homes will exceed expectations and add value for years to come.

End Notes

¹“NAHB/Wells Fargo Housing Market Index (HMI).” National Association of Home Builders®. June 19, 2024. https://www.nahb.org/news-and-economics/housing-economics/indices/housing-market-index. Accessed July 12, 2024.
²“National Housing Survey.” Fannie Mae®. July 8, 2024. https://www.fanniemae.com/research-and-insights/surveys-indices/national-housing-survey. Accessed July 12, 2024.
³Emrath, Paul. “Housing Affordability Challenges Leads to Frustrated Buyer Price Expectations.” Eye on Housing. National Association of Home Builders®. July 5, 2024. https://eyeonhousing.org/2024/07/housing-affordability-challenges-leads-to-frustrated-buyer-price-expectations/. Accessed July 12, 2024.
⁴Quint, Rose. “Preference for New Homes Keeps Rising.” Eye on Housing. National Association of Home Builders®. May 24, 2024. https://eyeonhousing.org/2024/05/preference-for-new-homes-keeps-rising/. Accessed July 12, 2024.
⁵Quint, Rose. “Buyer Preference for a Detached Home Remains Strong.” Eye on Housing. National Association of Home Builders®. April 22, 2024. https://eyeonhousing.org/2024/04/buyer-preference-for-a-detached-home-remains-strong/. Accessed July 12, 2024.
⁶Jones, Stephen A. and Donna Laquidara-Carr. “Building Sustainably: Green & Resilient Single-Family Homes 2024.” SmartMarket Brief. Dodge Construction Network. https://www.nahb.org/-/media/NAHB/advocacy/docs/industry-issues/sustainability/green-smartmarket-brief-2024.pdf?rev=1911eead2bcd4f309ef4b69c41f85071&hash=D0CE69C60CE8A31563278683C3E8BFAF. Accessed July 12, 2024.
⁷Araullo, Kenneth. “Majority of US homeowners face resiliency barriers as climate-driven events loom.” Insurance Business. October 10, 2023. https://www.insurancebusinessmag.com/us/news/property/majority-of-us-homeowners-face-resiliency-barriers-as-climatedriven-events-loom-462570.aspx. Accessed July 12, 2024.
⁸Quint, Rose. “Top Compromises Buyers Will Make to Reach Homeownership.” National Association of Home Builders®. May 13, 2024. https://eyeonhousing.org/2024/05/top-compromises-buyers-will-make-to-reach-homeownership/. Accessed July 16, 2024.
¹⁰Tracey, Melissa Dittmann. “13 Features New-Home Buyers Say Are Essential, Desirable.” National Association of Realtors®. March 1, 2024. https://www.nar.realtor/magazine/real-estate-news/sales-marketing/13-features-new-home-buyers-say-are-essential-desirable. Accessed July 16, 2024.
¹¹Quint, Rose. “Outdoor Features & a Laundry Room Among Most Wanted Features. National Association of Home Builders®. April 3, 2024. https://eyeonhousing.org/2024/04/outdoor-features-a-laundry-room-among-most-wanted-features/. Accessed July 16, 2024.
¹²Ibid.
¹³“Study reveals American consumers crave sustainable home design, yet consumer action is limited.” America at Home Study. Kantar. April 24, 2023. https://www.kantar.com/north-america/company-news/study-reveals-american-consumers-crave-sustainable-home-design-yet-consumer-action-is-limited. Accessed July 16, 2024.
¹⁴Jones, Stephen A. and Donna Laquidara-Carr. “Building Sustainably: Green & Resilient Single-Family Homes 2024.” SmartMarket Brief. Dodge Construction Network. https://www.nahb.org/-/media/NAHB/advocacy/docs/industry-issues/sustainability/green-smartmarket-brief-2024.pdf?rev=1911eead2bcd4f309ef4b69c41f85071&hash=D0CE69C60CE8A31563278683C3E8BFAF. Accessed July 17, 2024.
¹⁵Dereski, Onnah. “Green Building: Resiliency Practices.” National Association of Realtors®. April 22, 2024. https://eyeonhousing.org/2024/04/green-building-resiliency-practices/. Accessed July 17, 2024.
¹⁶Araullo, Kenneth. “Majority of US homeowners face resiliency barriers as climate-driven events loom.” Insurance Business. October 10, 2023. https://www.insurancebusinessmag.com/us/news/property/majority-of-us-homeowners-face-resiliency-barriers-as-climatedriven-events-loom-462570.aspx. Accessed July 17, 2024.
¹⁷The American Wood Protection Association (AWPA). https://awpa.com.
¹⁸“How to Specify Treated Wood Products.” The American Wood Protection Association. https://awpa.com/images/public/How_to_Specify_Treated_Wood.pdf. Accessed July 17, 2024.
¹⁹Jaugelis, Al. “Performance Class – The Key Concept at the Heart of the NAFS.” RDH. November 18, 2014. https://www.rdh.com/blog/performance-class-the-key-concept-at-the-heart-of-nafs/#:~:text=For%20these%20reasons%2C%20I%20think,on%20the%20basis%20of%20durability. Accessed July 17, 2024.
²⁰Chao Liu, Qiuyun Zang, Jiaxin Li, Xue Pan, Haoru Dai, Weijun Gao. “The effect of the acoustic environment of learning spaces on students' learning efficiency: A review.” Journal of Building Engineering, Volume 79, 2023, 107911, ISSN 2352-7102. https://doi.org/10.1016/j.jobe.2023.107911. (https://www.sciencedirect.com/science/article/pii/S2352710223020910) Accessed July 17, 2024.
²¹H.E. Laszlo, E.S. McRobie, S.A. Stansfeld, A.L. Hansell. “Annoyance and other reaction measures to changes in noise exposure — A review.” Science of The Total Environment, Volumes 435–436, 2012, Pages 551-562, ISSN 0048-9697. https://doi.org/10.1016/j.scitotenv.2012.06.112. (https://www.sciencedirect.com/science/article/pii/S0048969712009539). Accessed July 17, 2024.
²²“Study reveals American consumers crave sustainable home design, yet consumer action is limited.” America at Home Study. Kantar. April 24, 2023. https://www.kantar.com/north-america/company-news/study-reveals-american-consumers-crave-sustainable-home-design-yet-consumer-action-is-limited. Accessed July 18, 2024.
²³Dereski, Onnah. “Green Building: Resiliency Practices.” National Association of Realtors®. April 22, 2024. https://eyeonhousing.org/2024/04/green-building-resiliency-practices/. Accessed July 17, 2024.
²⁴Robbins, C. L. (1986) Daylighting Design and Analysis, New York: Van Nostrand Reinhold Company.
²⁵Mardaljevic, J. (2012) Daylight, Indoor Illumination and Human Behavior in Encyclopedia of Sustainability Science and Technology Springer-Verlag New York Inc, New York. ISBN 978-0-387-89469-0, pp 2804-2846.
²⁶Wirz-Justice, A., Fournier, C. (2010) Light, Health and Wellbeing : Implications from chronobiology for architectural design, World Health Design, vol. 3.
²⁷“Daylighting.” U.S. Department of Energy. https://www.energy.gov/energysaver/daylighting. Accessed July 18, 2024.
²⁸Walker, Andy. “Natural ventilation.” National Renewable Energy Laboratory. Whole Building Design Guide. August 2, 2016. https://www.wbdg.org/resources/natural-ventilation. Accessed July 18, 2024.
²⁹Ibid.

Amanda Voss, MPP, is an author, editor, and policy analyst. Writing for multiple publications, she has also served as the managing editor for Energy Design Update.