Advanced window systems and building energy performance

The influence of commercially available and prospective advanced window systems on a commercial building's energy performance in mild and cold German climates is studied. The advanced windows include multipane windows with sun-control and/or low- emittance glazings and low-conductivity gas-fills, transparently insulated windows, evacuated windows, and windows with electrochromic or thermochromic switchable glazings. Automated shading devices are employed to avoid excessive solar gains, along with lighting controls to take advantage of the lighting energy savings from daylighting. The shade control is inherent in the switchable windows. Total annual energy savings between 4% and 39% are reported is compared to a building with clear, air-filled, double- pane windows. The switchable electrochromic windows show the greatest potential energy savings.