Tuesday, November 6, 2012

What Is Low-e and How Does It Work?

What is Low-E Glass
Bellevue window replacement with energy efficient low-eLow-emissive (Low-E) glass is window glass that has been treated with an invisible metal or metallic oxide coating, creating a surface that wants to bounce heat back to its source, while allowing visible light to pass through. This energy-saving technology first became available in the early 80's and  is now required by code in all new construction. Windows treated with Low-E coatings can significantly reduce energy consumption, decrease fading of fabrics, such as window treatments, and increase the overall comfort in your home.

Not all Low-E coatings are the same, however. Some are designed primarily to keep heat out (useful in California) and some are designed more to keep heat in (Canada for example). Some Low-E films are designed as all around performers. Here at Window Defoggers, whether we are doing glass replacement or full replacement in a home or commercial building we may recommend different Low-E films for each side of the building, depending on its orientation to the sun. For example, a strong heat blocking Low-E for western exposures and a high performance insulating Low-E for the northern exposures.

How It Works
Seattle window replacement low-e performance
The amount of heat (infrared light) that passes through your window glass is indicated by the U-factor number. The lower the U-factor the more energy-efficient your glass is. This type of light is produced by the sun and generates heat in your home. Too much solar heat, especially during summer, can cause your air conditioning bill to skyrocket in order to keep your house cool. 

Low-E glass also reduces the amount of ultraviolet (UV) light that enters your home -the light wavelength that cause the bulk of fading - without blocking visible light. Conversely, in winter, Low-E glass reduces the amount of conductive heat lost through your windows from the inside of your home, reflecting the heat back into the house and keeping heating costs down. Depending on your home's heating and cooling needs, various types of Low-E glass have been developed to allow for high, medium or low solar gain.

How Low-E Should Be Installed
In warmer climates (or western/southern exposures), the Low-E coating should be applied to the third surface (the window surface you can touch on the inside of house is the first surface) to keep the sun’s heat out. While in colder climates (or northern exposures), the Low-E coating should be applied to the second surface to keep heat trapped in. This way, radiant heat is kept on the same side of the glass from which it originated.

Window glass is treated with either a hard or soft Low-E coating. Hard coat Low-E's are the older original type of coatings. Modern high performance Low-E coatings are now primarily soft coat.

Energy Efficient Windows
Seattle vinyl window replacementAll new windows installed must be energy efficient windows with low-e. So all new vinyl replacement windows in the Seattle, Bellevue, Issaquah & Tacoma Metro area come with some type of Low-e, typically a two coat Low-e like Cardinal 270. Higher performance, three coat low-e's like Cardinal 366 usually are an upgrade. Any window in your home or residence that receives direct sunlight like the west or south facing windows would benefit from upgrading to the Cardinal 366 low-e. All new double pane glass windows - whether they are in entry doors, sliding glass doors or normal windows - include low-e. For a free vinyl window replacement quote, contact us today!

For a free, no-obligation vinyl window replacement quote, call us today!