With fall in full swing, iconic images associated with the changing seasons are coming into view -- leaves changing colors, pumpkin patches and apple picking. Windows allow us a view of these wonderful seasonal changes, but they also pose a real challenge for commercial and home energy performance -- accounting for up to 50 percent of a building’s energy loss.

New window. Photo courtesy of Pat Corkery

With funding from the Energy Department, the National Renewable Energy Laboratory (NREL) is working to develop innovative insulating window film that preserves the view while increasing occupants’ comfort and saving energy. This research effort creates vacuum insulation films that use nano- to micrometer-sized vacuum capsules that are invisible to the human eye. The capsules are sturdy enough to be integrated with standard window plastics and applied like typical window tinting called low-emissity (or low-e).

Early estimates indicate that a millimeter thick layer results in clear insulation with values equivalent to R-20, which is equal to standard wall insulations. By combining vacuum insulation materials and processes with low-e coated plastic films, the new technology will boost the energy efficiency of current window retrofit technologies by as much as 80 percent at a fraction of the cost. Best of all, building and homeowners will not need to replace their windows.

Considering the billions of square feet of installed windows in the U.S., the NREL research provides a ripe opportunity for saving energy, reducing costs and cutting carbon pollution. The window technology is revolutionary and complex, but the simple benefits will resonate with architects and building occupants alike. The result: This window film could reduce building energy use by as much as 33 percent, creating a simple payback for window retrofits of less than one year.

The potential benefits of NREL’s vacuum insulation for windows is promising and could significantly contribute to the Department’s goal of reducing building energy consumption by 50 percent. This technology is a true game changer that preserves our ability to comfortably watch the world unfold out our windows.

Energy.gov