If you are getting ready to shop for windows for your new home, you may want to get prepared. Fortunately, glass and window companies have made vast improvements in the glass itself that help to reduce condensation buildup, uncomfortable cold drafts, and fabric fading.
Low-E glass works by reflecting heat back to its source. It does this by utilizing an ultra thin metallic coating on or in the glass.
Among other things, sunlight contains visible light, UV light, and infrared (IR) light. Visible light enables us to see things. Ultraviolet light damages your skin, wood, fabrics, and causes colors to fade. Infrared light is basically heat. Low-E glass has the ability to allow visible light to pass while blocking certain amounts of UV light and IR light.
The infrared light in sunlight is powerful. When it strikes an object it heats up. These objects can be your tile floors, furniture, sidewalks, patio furniture, etc. As these objects cool off, they emit a low-powered form of IR light. Low-E glass reflects this form of energy. In the summer this helps to keep your house cooler, as the heat from objects outside is kept outside. All objects in your home are heated (by either the sun or your furnace). This heat is also bounced back into your house by Low-E glass.
There are two types of Low-E glass: hard coat and soft coat. Tin is applied directly to the molten glass to make hard coat Low-E glass. It is “hard” to scratch the tin off the glass. The soft coat process commonly involves the application of a thin layer of silver while the glass is in a vacuum. This coating is delicate. Soft coat low-E glass is always sandwiched with another piece of glass. It can also oxidize if exposed to air. Argon gas is sometimes used to prevent this oxidation. This gas also acts as an additional insulator.
Low-E glass helps to reduce condensation on the glass. The inside surface temperature of the glass is warmer. The differences can be dramatic. Imagine a cold night with an outside temperature of 0 degrees and a 15 m.p.h. wind. The inside temperatures of different glass are as follows: single pane, 26 degrees; regular double pane, 35 degrees; hard coat, 49 degrees; soft coat, 62 degrees; with Argon gas, mid 70 degrees.
Low-E glass is worth the price, especially since one quarter of a house’s heat can be lost through windows. Purchase the highest quality low-E glass you can afford. (By Tim Carter)