The Lang Exterior, Inc.™ Guide to Energy Efficient Windows

Energy Efficient

• Argon is an inert gas which means it does not react with many other elements, and is about 25% more dense than air. That is why we offer Argon Gas as a glass option; the benefit of having the higher density gas between the panes of your new Lang Windows™ adds more insulation than just air.
• Krypton is a denser gas than argon, making it a better insulator. Like argon, krypton is chemically non-reactive and occurs only in trace amounts in the atmosphere. The name “krypton” comes from the Greek word meaning “the hidden one.”
• Our Low-E option is a heat-reflective coating that can add to the energy efficiency of a window. The Low-E glass on the interior pane of a window reflects heat back into the room, which makes the inside glass temperature closer to room temperature and can also help reduce heating energy costs.
• The R-Value is the resistance of a material to heat flow; the higher the number the better the insulating quality. This common measurement can be compared to U-Value by dividing 1 by the R-Value.
• Solar Heat Gain Coefficient (SHGC) is an energy performance rating that measures the fraction of incident solar radiation admitted through the total window unit. The lower the windows SHGC, the less solar heat transmits.
• UV radiation is the main source of fading furnishings, drapes, and carpeting. You get a better fade protection the lower the Ultra Violet Transmission (UV) number.
• The U-Value is a measurement of actual energy transmitting through the window. The rate of heat flow through a window; the lower the value, the better the insulating quality. U-Value can be compared to R-Value by dividing 1 by the R-Value. For example, an R-Value of 2 equals a U-Value of 0.5. R-Value is most commonly used to measure the total window units insulating value.
• The Visible Transmission is a performance rating between 0.0 and 1.0 that measures the amount of visible light transmitted through the total window unit. The lower the window’s VT, the more the window blocks light. For example, a VT of 0.5 would block half the light from entering the home.