The history of energy efficient windows comprises around 40 years of technological advances. It started when the United States was looking at ways to cut energy use, it became obvious that windows were a key source of heat loss. The US Department of Energy estimated that 25% of home heating costs were devoted to offsetting the effects of heat loss through windows.
Most home windows around this time were single pane windows with wooden frames. Homeowners in colder parts of the country sometimes reduced heat loss with storm windows installed over traditional windows.
In the late 1970s, multi-pane windows were introduced for energy efficient windows. Taking a cue from storm windows, multi-pane windows use the space between two or more layers of glass as an insulating layer. As multi-pane windows evolved, the space between layers was filled with argon or other inert gasses to improve their insulating properties.
Manufacturers soon learned that aluminum frames were poor insulators and led to significant heat loss. In the 1980s, manufacturers began to produce vinyl and wood-vinyl composite frames. These frames lowered the transfer of heat and again increased the efficiency of windows.
At the same time, manufacturers began to replace the metal spacers that held multi-pane windows apart. The metal spacers were a source of heat loss and they began to be replaced with foam or plastic spacers. These non-metallic spacers were better insulators and reduced heat loss and condensation.
In the late 1980s, low-emissivity (low-e) glass began to be used with energy efficient windows. Low-e glass uses a thin layer of metal oxide to create a barrier to infrared radiation. Low-e glass allows visible light to pass through glass, but keeps heat from escaping.
This brings us to today’s highly efficient windows. These window give their owners a great return on investment over time and are easy on the eyes as well.