Energy efficient windows not only save energy but also insulate against traffic and other disturbing noises. They increase the attractiveness and value of the house and protect furnishings. When considering replacing windows features to consider include the frame material, style of window, kind of panes, grid options, hardware, cost and complexity of installation.
Frame material
The choices of window frames include non-conductive solid wood, aluminum-clad wood with a thermal break, vinyl, wood-clad vinyl, a composite of vinyl and wood fiber, and fiberglass. Wood costs more than vinyl and requires painting or staining. Frames made from a composite of wood fibers and vinyl give the strength and durability of wood with the low maintenance of vinyl. Exterior maintenance can be minimized if clad in vinyl or aluminum. Vinyl may warp and has minimum options in colors. Aluminum frames conduct heat readily but better quality windows are "thermally broken" with insulating material between the interior and exterior components.
Styles of windows
In selecting replacement windows the style should be compatible with the house design and with other windows if not all are to be replaced. Styles include picture window, casement, horizontal slider, awning, and single and double hung windows. Even double hung windows that tilt for easier cleaning are available. Casement and awning types seal better when closed than sliding window and may be more expensive.
Panes
Double paned windows are treated with "Low-E" (low emissivity) coatings (such as metal oxide or microscopic layers of silver) deposited in a thin layer on the glass; or, a suspended plastic film is inserted between the two panes. Panes may have air, argon gas or argon/krypton gas between them. The coating must be on the inside of the sealed window unit to protect it from degradation by moisture. These coatings allow light and solar energy into the house, but reduce heat radiation through the glass. Heat flowing out of the house in winter, or into the house in summer is reduced. Other advantages of this reduced radiation are greater comfort, reduced condensation and reduced fabric fading.
Several ratings or numbers are used to measure the performance of a window. The U-factor measures thermal performance or ability to conduct heat; the R-value describes the insulating ability, the inverse of the U-factor. The higher the R-value, and the lower the U-factor indicate the better performing window.
Grids
Grid patterns can give the window a more classical look. They may be inside the glazing unit, snap-in wood grids attached to the interior side of the pane, or fiberglass grids applied to the exterior of the window.
Hardware
Hardware considerations include durability, eye-appeal, security, and ease of operation.
Some automatically lock when closed. Interior or exterior screens are available with some styles.
Complexity of installation
Standard sized windows would be easier to install and less expensive than custom windows that would require special order and additional construction or fitting. A good window poorly installed could still leak wind and rain. Details of installation include the type of perimeter seal and thermal barrier construction.
Cost
The cost of replacing each window may range from $100 to over $400. How much you want to spend depends on the basic value of your house, how long you intend to live in the house, how many windows you want to replace and the availability of a warranty. It may take twenty years to recoup the initial outlay through lower heating and cooling bills.
Source: Colorado State University Cooperative Extension
Debbie Wilburn is County Agent/Family and Consumer Science Agent with the Hall (770)535-8290 and the Forsyth (770)887-2418 County Extension Service.
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