Design
Patterns and Recommendations
 10.
Windows
–
Gaining energy
Windows are less thermally efficient than walls, yet they can provide
benefits such as solar heat gain and daylighting, as well as improving the quality of a
living space. Properly orienting window
placement within a design is one aspect of applying windows sustainably. (See Pattern 6.)
Another consideration is the makeup
of the window itself. National rating systems have been developed to provide a
standard measure of window performance, in terms of heat transfer, visible light
transmission, and solar heat gain coefficient. When
considering the thermal performance of windows, it’s important to consider the
performance of the window as a unit, including both the glazing and the frame. Unless the entire unit is efficient, a valuable
energy efficiency opportunity is wasted.
Recommendations:
§
Choose the most energy-efficient window the project budget will allow.
§
Orient windows with high solar heat gain coefficient on the building’s
south side in heating climates, as part of a passive solar design strategy.
§
Promote window durability by choosing low-maintenance windows with frame
materials that have a coefficient of expansion similar to that of glass.
§
Place windows to enhance daylighting.
§
Shade windows to prevent overheating from summer sun, yet capturing low-angle
winter sun.
Reference:
§
Efficient Windows Collaborative website
§
Energy
Star Windows
§ National
Fenestration Rating Council
§ Daylighting
Design, University of Kansas School of Architecture and
Urban Design online textbook
§ “Windows & Daylighting” from Lawrence Berkeley National Laboratory
§ Whole Building Design Guide
§
Florida Solar Energy Center Fenestration Research
Applied in Case Studies:
§ Metro Denver HFH “Green” Program
§ Erie-Ellington
Homes
Additional Examples:
§ The
Burnham Building
§ Colorado
Court
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