Numerous U.S. buildings have single-pane windows that do not insulate the building or its occupants as well as double-pane units or other advanced windows. Single-pane windows are also inferior in condensation resistance and occupant comfort. However, complete replacement of single-pane windows with efficient, modern windows is not always feasible due to cost, changes in appearance, and other concerns. Retrofitting, rather than replacing single-pane windows, can reduce heat loss and save roughly the amount of electricity needed to power 32 million U.S. homes each year. Window performance can be improved either by transparent, adhesive products that can be applied directly onto existing windows or by manufactured windowpanes that can be installed without replacing the window sash that holds the windowpane in place. Innovative technologies to enable inexpensive, high-performing products in these two categories are needed to accelerate effective retrofit options.
Project Innovation + Advantages:
Virginia Commonwealth University (VCU) will develop innovative methods to produce aerogel-on-glass windowpanes for window retrofits. Silica aerogels are porous materials that can be used to control heat transfer across windows. However, widespread use of silica aerogels in windows has been limited by their mechanical fragility, difficulties with transparency, and high manufacturing costs. The team will use newly developed cross-linked aerogels that significantly improve the mechanical strength and durability of aerogels. Aerogels are typically produced through either air drying or supercritical drying. Air drying is inexpensive, but induces stresses that can lead to fragmentation. Supercritical drying is superior, but is expensive. VCU will employ an alternative drying method, freeze drying, in which the material is frozen and ice is sublimated off. VCU estimates that aerogel production using freeze drying can cut production costs by about 40% compared to supercritical drying. VCU’s aerogel material would be placed between a glass pane and polycarbonate films to produce an effective windowpane for single-pane window retrofits.
If successful, VCU’s innovations will enable energy-efficient retrofits for the substantial remaining stock of single-pane windows in the United States. Retrofitting single-pane windows could produce significant economic and environmental benefits. These technologies could help reduce building energy consumption and save money for homeowners and businesses. Consumers adopting these retrofits could also benefit from improved window performance, including greater comfort and condensation resistance in cold weather and better soundproofing. Finally, by consuming less electricity, natural gas, and/or heating oil to warm a building, these technologies reduce the greenhouse gas emissions associated with using these energy sources.