Window Shopping

Windows have come a long way during the last 40 years in terms of energy efficiency and maintenance. If your current windows have aluminum framing or single-paned glass, it may be time to consider replacement windows.

The first thing to check is the soundness of the framing. If the elements around the window – jambs, sills, trim and siding – are free of rot or other problems, you can go with pocket windows (also known as frame-and-sash or replacement windows.) Rot or moisture issues call for new-construction windows installed in the rough openings.

Good measurements are key in window replacement. Even if you have a sales rep or contractor coming to your house, be sure to have your own notes to double check their work. Each window should be individually measured for height (left, right and middle), width (top , middle and bottom) and diagonal (both ways to check for square). Each replacement window will be sized according to the smallest measurement.

The most energy efficient framing materials are vinyl or fiberglass, but there are also clad-type frames (wood indoors, vinyl outdoors) that do a good job. In our hot-humid climate, double-paned, insulated glass with a low-e coating will provide the most thermal protection. Single-paned, clear (no coating) glass leaks energy like a sieve.

When shopping, the numbers you’ll need to compare are called U-Factor and Solar Heat Gain Coefficient (SHGC). A U-Factor rates the heat conductivity of the window assembly from 1.0 to 0 – the lower the U-value, the better. The Solar Heat Gain Coefficient (SHGC) measures how well the window blocks infrared heat – again, lower is better. Energy Star windows for our climate zone must have a U-Factor of 0.65 or less and a SHGC of 0.4 or less. Every window should have a National Fenestration Rating Council (NFRC) label showing these values.

One last important piece of information you’ll need is the window’s Wind Rating. This is the design standard for wind loading in extreme wind events such as hurricanes. Ratings are specific to location and can be found on the International Residential Code (IRC) Wind Hazard Zone map for Louisiana. Click here to see more information from the LSU AgCenter on Louisiana Wind Hazard Zones.

Proper installation of your replacement windows will have a large impact on their energy efficiency. Improperly installed windows leak lots of energy, air,humidity, and rain water making a house uncomfortable and more expensive to maintain. The do-it-yourself route is only for folks with some experience in carpentry or larger household projects. A short tutorial on installing your own replacement windows can be found on the Lowe’s website. Hiring a contractor is probably the best choice for most homeowners – installers typically guarantee their work for a year. There is currently no industry standard for replacement windows, which means that “workmanship” is open to a lot of interpretation. Hire a contractor who has experience installing replacement windows and can provide local references for their services.

Efficient Windows Collaborative and Energy Star are both excellent sites for more information on replacing windows.

This blog was written for Paul LaGrange’s BuildWrite website and was originally posted on February 3, 2009.


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