C042 -- Highly Insulating Commercial Window Demonstration; Energy and Comfort Analysis PDF

Berkeley Lab has shown through previous simulation studies that 5 – 30% of typical perimeter zone floor area of commercial buildings may be uncomfortable in heating design conditions due to the relatively cold room-side surface temperatures on current code-compliant double-pane low-E windows. The large discrepancy in thermal performance between typical walls and windows results in higher energy use and discomfort through radiative and convective loads from windows. In this project, the benefits of highly insulating commercial glazing are demonstrated through the installation and real-world performance measurement of the most advanced highly insulating commercial glazing technologies on the market today; including triple-pane, quad-pane, quint-pane, VIG, hybrid-VIG, and high-performance secondary glazing systems.

The subject commercial building is a three-story over partial basement with a total of roughly 20,000 sqft located in Boulder CO. Windows on the second floor were replaced with high-performance products. This paper is a summary of field measurements taken over the course of two years and compared with simulation studies to determine the validity of previous comfort research and assist in future comfort and energy-use-related window research. The field measurements showed that the surface temperature (COG) of these products are close to the indoor environment despite the cold weather outside in winter nights. The thermal performance simulated for these products indicated ~74% reductions in assembly U-values compared to double-pane low-E windows. Modeled results suggested significant improvements in indoor thermal comfort with these products.