The Benefits of Insulated WindowsOctober 29th, 2010 | Posted by in Environment | Fuel Efficiency | Green Building | Green Homes | Green Products
As tightly as we might insulate our homes – filling every nook with environmentally-friendly fill insulation, and caulking every crack and draft – windows are still a major drain on heating and energy bills.
The R-value is the standard unit of how insulating a construction material is. Conventional fiberglass battens typically have an R-Value of 10.9; some more-efficient green insulations can have R-Values up to 13. An average glass window has an R-value of one, meaning that a significant amount of energy can pass through a standard window. Researchers have determined that windows in the U.S. consume about a third of a building’s heating and cooling energy – roughly 4.1 quadrillion BTU of energy.
So, upgrading windows to super-insulated ones presents an opportunity to substantially reduce energy-consumption and lower the cost of heating and cooling a home.
Most LEED-certified buildings use insulated glass. These are windows with two or three panes stacked in the frame. The space between panes traps air and significantly increases their efficiency, sometimes providing an R-value rating of two or three. The most efficient standard insulated glass windows have argon or krypton gas between the panes.
The most efficient type of insulated windows are vacuum glass panels under development by Guardian Industries, and expected to arrive on the market by the end of 2010. These work on the same physical principle as a thermos bottle – by creating a vacuum between panes of glass, energy cannot transfer through by convection or conduction. The panes are then coated with a material that reduces radiative heat transfer, providing an R-value of up to R-13. That means a vacuum-glazed window is as insulating as a brick wall, and can help add thermal energy to a house, instead of leaking it – sort of like a garden greenhouse.