Energy Efficient Windows to Reach Market Quicker with New Tool

April 5, 2016

About 10% of the energy used in U.S. buildings—approximately 4 quads a year—compensates for energy lost through windows. To address this inefficiency, architects, engineers, and home-builders are advocating the use of high-performance windows, which are composed of insulated glass units (IGUs) that combine multiple panes, thin film coatings, and special gas fills between the panes, and insulating frames to lessen unwanted heat transfer while selecting for other properties, such as transmittance of visible light and solar heat gain. The optimal IGU properties vary widely, depending on factors such as climate zone, orientation of the building, and building use.

In the past, calculating IGU performance—including the amount of heat transmitted through the unit, solar heat gain, and transmittance of visible light—was a cumbersome and complicated process. To address this information barrier and accelerate the uptake of high performance IGUs, PPG Industries, in partnership with the Lawrence Berkeley National Laboratory (LBNL) and the U.S. Department of Energy's Building Technologies Office, released an enhanced, user-friendly, online tool that helps architects and builders select and specify IGUs that suit their needs within seconds. PPG eView Construct incorporates LBNL's WINDOW 7 software engine and is backed by North America's largest repository of glass-product performance data which was developed by LBNL with the cooperation of PPG and other glass manufacturers. Construct allows users to mix and match glass, coatings, and gas fills into a virtual IGU design and to virtually analyze performance under standard NFRC environmental conditions. Users can perform side-by-side comparisons of multiple IGUs and export reports of their selected IGUs for easy inclusion into bids.

"Construct is a great example of DOE's tool development strategy in action," says Amir Roth, Technology Manager for Building Energy Modeling in the Building Technologies Office of DOE. "Our goal is to give the market the foundational engines that they can then use to build applications that target specific market needs. Products like Construct bring advanced modeling capabilities to the market in a focused, user-friendly way, enabling more building industry professionals to use them."

"The Construct tool is a state-of-the-art glass specification tool that architects and other glazing-industry professionals can use anonymously to build virtual IGUs. Glass products from PPG and other glass manufacturers in the LBNL WINDOW 7 database can be viewed for side-by-side comparison of color, aesthetics, and critical performance data", says Paul Bush, Director of Technical Services at PPG. "PPG appreciates DOE's investment in these tools, which allow our industry to meet the growing popularity of building information modeling in conjunction with the proper specification of products."

Berkeley Lab WINDOW is part of a suite of window performance analysis and modeling tools that LBNL has been developing as part of its decades-long work on windows—work that includes the commercialization and widespread market adoption of low-emissivity, or "low-e," window coatings that reduce glass heat transfer. Over 80% of residential windows and 50% of commercial windows now incorporate low-e coatings, which dramatically cut unwanted heat loss and heat gain, and the resulting total building energy use. PPG's Construct tool makes it easier for architects and builders to incorporate low-e coatings and other energy-saving window features into new construction and retrofit projects.

Technology Overview


in October 2015 PPG Industries upgraded their IGU selection tool, eView Construct, with Berkeley Lab's WINDOW 7 engine and its glazing database.


  • Lawrence Berkeley National Laboratory
  • PPG Industries


  • WINDOW software enables performance analysis across manufacturers of window components
  • Construct's side-by-side comparison allows for multiple window performance criteria to be evaluated and optimized


  • WINDOW allows users to estimate performance of a new window without building a prototype, saving time and money
  • User-friendly online tools such as Construct make robust analysis capabilities available to a larger user base