High-Tech Windows
All windows are low-emissivity (low-E), tuned by orientation. Low-E windows have a film "sputtered" onto the inside surfaces of a double paned window, which reflects heat out in the summer and into the space in the winter, increasing the insulation value of the window. Windows with specific solar heat gain coefficients further determine how much heat can enter through the windows.
Fixed glass is Heat Mirror™. This is a special type of low-E glazing made by suspending a thin plastic film link shrink wrap between two panes of glass with low-E coatings on all interior surfaces. The window is then filled with inert gas, to reduce the movement inside the window that leads to increased heat loss.
Diary Entries
You can read more about David's remodel experience and learn valuable knowledge about green building standards, materials and best practices in his book Green Remodeling.
April 7, 2003 - Choosing High-Tech Windows
Window technology has advanced dramatically in the last 20 years. Today, average windows are twice as efficient as those in the 80's. That still isn't good enough for me. I want the addition to be as bright and energy-efficient as possible, therefore high-tech windows are my best option. I choose low emissivity (low-E) windows with specific solar heat gain coefficients (SHGC). I use low-SHGC windows for the east and west windows that tend to be the hottest, so that I can enjoy the view overlooking the plains without cooking in the summer. I use high-SHGC on the south facing glass to maximize solar heat gain in the winter and keep my office warm; the sun is low enough in the sky that the overhangs that block unwanted sun in the summer will not obstruct this winter light.
I install Heat Mirror™ for all the fixed glass, or glass windows that do not move or open. The down side of the heat mirror is that it requires a metal spacer between the panes of glass because of the tension of the plastic film; in turn, the spacer tends to lose heat through conduction. To counter the transfer of heat through the metal, I buried the the spacer in wood trim.
