When you hear “aluminum windows,” the first thing that comes to mind is the cheesy, usually ugly products that were the hallmark of bad late-20th-century construction and remodels-on-the-cheap of fine old homes. In fact, aluminum windows have come a long way in recent years, and can be positively stylish. Architects like them because the strength of the metal frame, relative to such materials as vinyl or wood, allows for a narrower frame, and thus a bigger expanse of glass.
Also, the unattractive bare-metal finish you may associate with aluminum windows is a thing of the past: not only can they be painted whatever color you like, they’re often available from the factory in a various shades of baked-on enamel. Some manufacturers also offer vinyl-clad aluminum windows, an option that reduces maintenance to practically nil.
Still, if you’re thinking of replacing existing windows in your home - aluminum or otherwise - aluminum may not be your best option. Keeping up the frame’s painted surfaces can be a hassle, if you go for that option. But the biggest issue is energy efficiency, where aluminum just doesn’t measure up to the alternatives.
The very properties of aluminum that are a real asset in other situations - the fact that it’s a very efficient conductor of heat and cold - aren’t such a boon here, as it very efficiently conducts the outside temperature into your home instead of keeping it out. In cold weather, this also leads to condensation of moisture on the chilled glass, or even frost.
Good design and materials can mitigate the problem somewhat - using double-glazed low-E, low solar gain, argon-filled panes greatly reduces heat gain even when the metal frame gets quite warm.
Further, some products use what’s called thermal break frame design, in which the aluminum interior and exterior are separated by non-conductive material to prevent heat or cold transfer. This too improves the window’s energy efficiency.
The bad news is that these windows (in Milgard’s product line, “Thermally Improved Aluminum Windows”) may not be available in your area. Milgard, for example, does not offer them in California, and you may be hard pressed to find a vendor who does. And even these windows’ performance compares unfavorably with their wood and vinyl counterparts - according to a study by the University of Minnesota’s Efficient Windows Collaborative, the most energy-efficient double-glazed window of this type has a U-factor of .47, and .40 or less is desirable. Vinyl and other windows commonly run in the .30-.40 range.
Don’t be tempted by incredible bargains on replacement aluminum windows at your home improvement store. For one thing, they’re usually from the manufacturer’s lower-quality line, and likely to be flimsier and less energy efficient. For another, you may have trouble finding a qualified pro to install them because they’re aware of potential problems and don’t want to be responsible for dealing with them down the line.
In order to get the best value for your investment, shop around. Compare NFRC labels to see how several different windows match your needs. Don’t accept anything that doesn’t have Energy Star certification. And before you put down your money, consult with a qualified building professional who’s familiar with your local building code requirements so you don’t wind up with windows the city won’t accept. Our CalFinder certified window experts are ready to help.
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