Rarely do we think about the windows in our home or cabin and how they save us money. Technological advancements in the construction of energy efficient windows in the past 40 years have allowed the average homeowner to save several hundred dollars per year thanks to reduced power consumption. Many of the advancements have been applied to wooden window designs that keep a mountain cabin looking rustic but comfortable at the same time.
The quest for energy efficiency in our cabins, homes and workplaces truly began in earnest during the “energy crisis” of the 1970s. Many people, especially in large urban areas, experienced rolling blackouts and sky-high energy bills. One of the proposed remedies to reduce energy usage was to make homes and businesses better insulated to retain more of the energy they consumed rather than losing energy to the environment. It has been estimated that 25% of the energy loss of a structure was due to uncoated, single-pane windows which are highly emissive.
The first major advancement toward a more energy efficient window was taken from the storm window industry, which had long used two panes of glass separated by a spacer. However, using two panes of glass was not enough, as convective heat loss would occur between the panes. Eventually these windows were sealed between the panes and the air was withdrawn, creating a vacuum. Although this improved the loss of heat through convection, it was found that filling the void between the panes with an inert gas such as argon, krypton, or xenon was much more effective in preventing heat loss.
The next major advancement in window construction was taken from the sunglass industry, which had been experimenting with glass coatings for many years in order to reduce glare and harmful ultraviolet rays on the human eye. When some of these coatings were applied to residential windows, there was a dramatic reduction in heat gain during the summer and a reduction in heat loss during the winter. Although there are many types of these glass coatings in use today, they are collectively called “Low-e” for low emissivity. They work by selectively rejecting most UV rays while allowing visible light and some solar heat to pass through. Additionally, the Low-e coating on the interior side prevents the loss of energy to the outside world. According to the Center for Sustainable Building Research, the most thermally efficient units currently in production utilize three panes of glass, each coated with a low solar gain coating. These windows are typically more expensive than double glazed models; however, additional savings can be realized by reducing the size of heating and cooling units required for the structure.
Future research for a more energy efficient window is focused on the use of sensors inside the window that will respond to changes in the environment, including temperature, humidity, season, and even daylight and dark. These “smart windows” will be integrated into a central computer system in the home, allowing control of the interior environment. It may sound like science fiction, but it is quickly becoming a reality.
In summary, technological innovations in the construction and production of energy efficient windows since the 1970s have allowed homeowners to realize lower energy consumption and more stable environments inside their homes. State and Federal government agencies have recently begun offering tax incentives to encourage the use of high efficiency windows to decrease power demand. With all of these benefits, it pays to find out if you should replace your old windows and put more money back in your pocket.