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
High R-value windows (R-5) reduce average heat loss by 30 percent, lowering heating, ventilating, and air-conditioning loads. Those with spectrally selected coatings further reduce energy expended on HVAC.
The two “smart window” technologies evaluated here promise to reduce overall cooling loads by up to 20 percent.