Monitored thermal performance results of second generation superwindows in three Montana residences. Final report: High-R window technology development, Phase 2B.

摘要

Simulation studies have shown that highly insulating windows with moderate solar transmittances (R values greater than 6 hr-ft(sup 2)--F/Btu and shading coefficients greater than 0.5) can outperform insulated walls on any orientation, even in a northern US climate. Such superwindows achieve this feat by admitting more useful solar heat gains during the heating season than energy lost through conduction, convection and infrared radiation. Testing of first generation superwindows in three new homes in northern Montana during the winter of 1989--1990, reported in an earlier study, indicated that the glazed areas of superwindows can in fact outperform insulated walls on obstructed off-south orientations. However, this same study also showed that further improvements in the thermal performance of window edges and frames are necessary if the entire window is to outperform an insulated wall. As a result, second generation superwindows with improved frame, edge, and glazing features were installed in these houses during the summer and fall of 1990 and these windows were monitored during the winter of 1990--1991. Results from this monitoring effort, discussed in this paper, showed that while small performance improvements may have been made with these second generation superwindows, the frame and edge still limited performance.