EERE Success Story—Energy-Efficient Windows are Saving Americans Billions of Dollars

April 19, 2017

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Low-E windows – featuring an energy-saving technology developed in partnership with Berkeley Lab – are now found in 80% of windows sold each year to homes and 50% of sales to commercial buildings in the United States.

Low-E windows – featuring an energy-saving technology developed in partnership with Berkeley Lab – are now found in 80% of windows sold each year to homes and 50% of sales to commercial buildings in the United States.

For the past 40 years, Lawrence Berkeley National Lab (LBNL) has been partnered with the window industry to help save American consumers money in energy costs by pioneering new energy-efficient windows, design tools, and window-rating systems. The lab worked closely with window manufacturers and the building industry to develop, produce, validate, and deploy energy-saving low-emissivity or "low-E" coatings. Today more than 50% of window sales in the commercial market and 80% of the sales in the residential market incorporate low-E coatings, which can reduce window energy use by 30-40%.

The Opportunity: Moving Theory into Practice

LBNL’s involvement with window innovation started with a brainstorming session during the energy crisis of the 1970s. Physicist Steve Selkowitz and LBNL’s building energy efficiency team realized a huge amount of energy was being lost through conventional inefficient windows. They identified a possible fix: the military had explored the concept of using “low-E” coatings, made of metal and metal oxide layers, to reduce heat transfer through glass surfaces. Could low-E coatings applied to windows help to insulate buildings?  

“The concept and some of the materials and patents were already out there,” Selkowitz said. “But the theory had to be turned into practice – moving from a good idea to viable products and production processes that could be deployed at scale to save large amounts of energy at affordable costs.”

The Pathway: Lab Expertise Shows Windows Industry the Potential

With U.S. Department of Energy (DOE) funding, LBNL initially worked with start-up companies who were developing the low-E coatings and the low-cost, thin-film deposition processes needed to scale up production. But these in-the-lab research efforts paled in comparison to the real-world business and market challenges the Berkeley Lab team faced.

“There was a marketplace problem,” Selkowitz says. “The low-E glass manufacturers didn’t make windows. The window manufacturers didn’t do coatings. And potential customers did not yet understand how much energy and money you could save by simply installing better windows with low-E coatings, nor were they confident that an “invisible” coating could deliver those big energy savings.”  

The scientists crafted simple measuring tools that showed how well low-E glass insulates buildings and demonstrated the technology to window manufacturers, selling companies on its importance. As Selkowitz puts it, his team became “the evangelists of low-E windows.”

The Breakthrough: Sales Go Up, Costs Come Down

Early on, only a few innovative firms began making low-E windows designed to save energy. Then one leading manufacturer, and eventually most large window manufacturers got in the game. As energy-efficient window sales went up, costs came down, and low-E windows grew more popular. By the mid-1980s, almost every U.S. window manufacturer offered some low-E, energy-saving window product lines. Coating and glass manufacturers developed different low-E coatings, some targeted for northern, heating-dominated climates and others optimized for southern, cooling-dominated climates. 

To accelerate market uptake of low-E windows and other efficient window products, LBNL has worked with the windows industry and DOE to create better tools, metrics and standards.  LBNL provides the tools used by the National Fenestration Rating Council to rate and label windows, supported the DOE/Environmental Protection Agency’s Energy Star Windows program, and partnered with numerous windows manufacturers to encourage further innovation. Through these initiatives and partnerships, LBNL has used its research, software, engineering, testbeds, and simulation tools to, inform building codes, and accelerate the development of new products.

In a past partnership, Silicon Valley-based View® worked with scientists, engineers and organizations, including LBNL, on a next generation of glass. The work contributed to the development of View Dynamic Glass® by View that the company now manufactures in Olive Branch, Mississippi. View Dynamic Glass® tints either automatically, in response to changes in sunlight; or on-demand, in response to preferences programmed through interfaces such as tablets or smartphone apps.

“View Dynamic Glass enables unmatched control over the amount of sunlight that enters a building, providing people with comfort and enhanced productivity without the intrusion of glare and unwanted heat, while helping tenants and building owners reduce energy costs,” said Robert Rozbicki, Chief Technology Officer at View. “We’re proud and fortunate to have collaborated with LBNL and others on a technology that is vital to the health of people, buildings and the environment.”

The Impact: 1.5 Quads of Energy Saved Annually

Window innovations developed in collaboration with LBNL save American families, businesses, institutions, and governments money, year after year. Low-E coatings alone reduce the energy lost through typical windows by 35%, resulting in an estimated 1.5 quads US annual energy savings. Andersen Corporation, one of the nation’s leading manufacturers of windows, has partnered with LBNL again and again to create and improve their low-E product line.

“Performance and innovation are central to the Andersen windows brand, and low-E windows are a key part of that,” said Mark Mikkelson, Director of Corporate Regulatory Affairs at Andersen Corporation. “We offer a variety of energy-saving, low-E glass options that are popular with customers because they offer greater control over heating and cooling costs, and improve comfort, in every climate.  We’ve partnered with Berkeley Lab since the 1980s to make low-E windows a reality, and we plan to continue that collaboration on innovation going forward.”