As a thermal barrier, the building envelope plays a critical role in regulating interior temperatures and helps to determine the amount of energy required to establish a comfortable indoor environment. In commercial buildings, the space heating, cooling, and ventilation that maintain that environment account for 34 percent of energy used on site and 31 percent of primary energy use, according to the U.S. Department of Energy. By evaluating technologies such as “smart windows” and “high R-value windows,” which directly influence HVAC requirements, the Green Proving Ground program is finding ways to make the building envelope more efficient.
Preliminary Technology Assessments
The Green Proving Ground program, in association with federal laboratories, is currently subjecting the following technologies to real-world measurement and verification in GSA buildings. Preliminary technology assessments are available below as PDFs. Findings from these investigations will be available by 2015.
Electrochromic Windows > Electrochromic (EC) windows switch from a clear to dark state with a small applied voltage, and promise to optimize daylighting, visual comfort, and solar heat gains without the need for blinds. Window tinting can be controlled manually (using a button or switch), or by an automated building control system, which programs sensors to respond to changing sunlight levels and heat conditions.
Glazing Retrofit Coating > This clear, water-based spray-on window coating molecularly bonds to existing windows surfaces, and is designed to reduce heat gains across the entire solar spectrum without significantly reducing transmittance of visible light.