New windows would save $15 bil/year

In terms of energy efficiency, windows are one of the biggest contributors to heat loss from buildings.

But a new window technology called vacuum-insulated glass (VIG) being developed by Guardian Industries could allow for windows that can provide insulation values comparable to walls, thanks to a new double-pane glass with a vacuum between the panes.

The principle behind the Thermos, namely that a vacuum is a very effective insulator, is now being applied to windows, which are one of the most energy-inefficient parts of a building, responsible for up to 30% of the heating needed.

Heat is transferred by one of three methods, conduction, convection, or radiation. A vacuum prevents transfer by convection or conduction, and a low-E coating on windows can block much of the radiation transfer.

The manufacturer, Guardian Industries, is hoping to have this glass commercially available by the end of 2009. More importantly, while other researchers have been exploring the idea of vacuum glass for several years, Guardian is expecting to be able to produce this glass at a reasonable cost.

The head of the Building Technologies Division at Lawrence Berkeley National Laboratory notes:

This performance level would convert most windows in heating climates into net energy suppliers, providing more energy to the home via passive solar gain (even facing north) than the window loses ... If you could convert every window [in the U.S.] to this performance level, you would save homeowners about $15 billion each year.

via: BuildingGreen.com

A longer version of this article is cross-posted at Green Building Elements