HOTELS-INFORM

Since the energy shortages of the 1970s, scientist and manufacturers have worked to create energy efficient replacement windows and windows used for new home. Significant changes have been made in the design, materials and construction methods used to make energy efficient windows.
According to the US Department of Energy, up to 25% of a home's heating and cooling energy is used to offset the effects of windows in the home. Inefficient windows allow heat to enter the home in winter and heat to escape the home in winter. Energy efficient windows make sense from an economical, as well as ecological, perspective.

Enhanced Glass

Developed in the 1980s, Low-emissivity (Low-e) glass is created by coating one side of a pane of glass with a thin layer of metallic oxides. This layer is transparent to visible light, but reflects infrared light. By placing the coated side of the glass on the inside of the window, low-e glass can reduce the amount of heat lost through the window. Low-e windows have become a very popular option since their introduction.

Layered windows are also a popular technology in today's energy efficient windows. Layered windows sandwich multiple panes of glass (typically two or three) in a single window. The spaces between windows act as an insulating layer, blocking the transfer of heat. Manufacturers often fill the space between the glass panes with argon or other inert gasses. This gas layer insulates better than air, increasing the efficiency of windows.

Spacers To The Rescue

Small blocks called spacers separate layered window glass. Early layered window spacers were made of metal. Metal is a poor insulator, however, and early window designs lost heat around the edges of the glass. Current spacers are created of nylon or other insulating materials to reduce heat loss around windows.

The Future of Energy Efficient Windows

The next generation of energy efficient windows will feature innovative coatings that will allow the window to transform based on environmental conditions.

Currently in development, absorbing electrochromic (AE) windows use a thin layer of material that changes color under a tiny electric current. A light sensor in the window would control the electrical current. AE windows would be transparent during low-light conditions, but would turn darker in sunlight.

A similar technology, transition-metal switchable mirrors (TMSMs) apply a coating that turns reflective under an electrical current. TMSM windows would block heat gain on the inside and reflect solar heat on the outside.