Clear vs. Low-E Dual Glazing

These two windows are both double glazed and have the same size gap between the panes. The one on the left has normal clear glass and an aluminum spacer, while the one on the right has low-E coated glass and an insulating spacer. The cold regions (purple and black colors) on the left unit result from large amounts of heat flowing through the spacer. This cold region will also be the site of water condensation on the surface facing indoors. The low-E window is warmer because of the increase resistance to heat flow caused by the special transparent coating on one of the inner surfaces of glass. These windows are being cooled on the back side with wind at -17.8°C (0°F).

For more information contact:

Howdy Goudey
Building Technologies Program
510-486-6046 (fax)

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Building Technologies | Energy & Environment Division | Lawrence Berkeley National Laboratory

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