Improving the thermal performance of vinyl-framed windows
Over the last five years, vinyl-framed windows have gained an increased market share in both new and retrofit residential construction. This success has been mainly due to their low manufacturing cost and relatively good thermal performance (i.e., total window U-values with double glazing between 0.50 Btu/h[center dot]ft[sup 2][center dot][degree]F [2.86 W/m[sup 2][center dot]K] and 0.30 Btu/h[center dot]ft[sup 2][center dot][degree]F [1.70 W/m[sup 2][center dot]K]). Turning such windows into superwindows,'' windows with a U-value of 0.20 Btu/h[center dot]ft[sup 2][center dot][degree]F (1.14 W/m[sup 2][center dot]K) or less that can act as passive solar elements even on north-facing orientations in cold climates, requires further significant decreases in heat transfer through both the glazing system and the frame/edge. Three-layer glazing systems (those with two low-emissivity coatings and a low-conductivity gas fill) offer center-of-glass U-values as low as 0.10 Btu/h[center dot]ft[sup 2][center dot][degree]F (0.57 W/m[sup 2][center dot]K); such glazings are being manufactured today and can be incorporated into existing or new vinyl frame profiles. This paper focuses on the use of a state-of the-art infrared imaging system and a two-dimensional finite-difference model to improve the thermal performance of commercially available vinyl profiles and glazing edge systems. Such evaluation tools are extremely useful in identifying exactly which components and design features limit heat transfer and which act as thermal short circuits. Such an analysis is not possible with conventional whole-window testing in hot boxes where testing uncertainties with superwindows are often greater than proposed improvements.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098; AI79-86BP63401
- OSTI ID:
- 6731273
- Report Number(s):
- LBL-32782; TA-293; CONF-921239-2; ON: DE93007660
- Resource Relation:
- Conference: American Society of Heating and Refrigerating, and Air Conditioning Engineers/Department of Energy (ASHRAE/DOE/BTECC) thermal performance of the exterior envelopes of buildings 5 conference, Clearwater Beach, FL (United States), 7-10 Dec 1992
- Country of Publication:
- United States
- Language:
- English
Similar Records
A superwindow field demonstration program in northwest Montana
High-R Window Technology Development : Phase II Final Report.