What should you look for in an energy-efficient window? There are qualities in the frame, gases, panes and glass of an energy efficient windows that the home owner should look for. There are several things...
There are several things to consider when choosing an energy efficient window. One is the frame, one is the glazing or number of panes, and another is the low solar gain coating that some windows utilize. Energy efficient window expert Steven Poitz offers his advice.
"Starting with the glass and moving out to the frame: an energy efficient window should have low-E or low emittance glass. It may have two panes or it may have three panes. It would typically be gas-filled, usually with Argon because it's used in welding, it's widely available, and it is fairly inexpensive. In some specialized applications, the gas might be Krypton, but that is more expensive and would only be used in special situations." Triple glazed windows offer the highest level of energy efficiency, comfort, and decreased chance of condensation.
"One thing that is important to look for in an energy efficient window is the spacer. The spacer is the part of the window that holds the two or three panes apart from each other. If it is a double glazed window, there will be a little bar about half-an-inch wide that separates the two panes. If that bar is metal, it is not an energy-efficient window because metal is a conductor, not an insulator. So, an energy-efficient window would have a spacer that does not have any metal in it. That has the added advantage of dramatically decreasing wintertime condensation because it is warmer around the edge. Condensation always happens at the edge, so you are working on a weak link in the chain," Poitz adds.
The coatings applied to the exterior glass are another thing to look at when choosing an energy efficient window. Some windows will have a low solar gain coating that is basically a very thin layer of metal that aids in the window's ability to absorb heat in the winter and reflect light in the summer. There are also tints that are applied to reduce the effects of summer sun on the window's temperature. Some windows even have low-E coatings between layers of glass. These coatings and tints should be not limit the light or visibility through the window. It should be noted that these coatings are more important for windows on the east and west facing sides of the home.
The next consideration is the material the frame is made from. Wood, vinyl, and aluminum frames can be energy efficient, but top of the line energy efficient windows usually utilize fiberglass frames because fiberglass can be specially treated to increase energy efficiency and because it is a very strong and durable material able to support the heavier weight of multiple panes of glass.
One more consideration when choosing windows for your home will be size availability. Some materials have restrictions relating to size that may not be appropriate for the existing openings in older homes. For example, triple glazed casements have a width of 30 inches.
On the subject of price, Poitz says that energy efficient windows generally cost 15% more than regular windows. Triple glazed windows cost about 5% more than double glazed, or paned, windows. When considering the cost of your new windows you should also factor in the savings generated by decreased heating and cooling energy use.
