Until recently, aluminum-framed windows have usually meant that a home was built in decades after WW II.
Aluminum framed windows have been making slow gains an appreciation for the midcentury modern style has revived. Modern contemporary, too, is another style that values the distinctive spare, angular look of aluminum windows.
But aluminum windows are not for every home and definitely not for every region. Learn the basics of residential aluminum-framed windows with these facts:
|Aluminum's strength means thinner frames, larger windows.|
|Some windows are not aluminum-framed but wood clad in aluminum.|
|Anodizing penetrates like stain for wood; gives aluminum windows a "metal look."|
|Aluminum windows without thermal breaks only work in temperate climates.|
|Aluminum windows in harsh climates must have a thermal break.|
|Most aluminum windows are new-construction, not replacement.|
Stronger Materials Allow For Thinner Frames, Larger Openings
Windows should be about light and air, not frames. Since frames are a necessary element, the trick is reducing their presence as much as possible while maintaining structural integrity.
To make vinyl windows stronger, manufacturers add even more vinyl in the form of larger frames, in addition to supporting metal inserts.
Aluminum has been extruded for windows since the 1930s. During extrusion, a billet (or unformed chunk of aluminum) is forced through a die by pressure and heat. Extrusion allows for more complex, unified dimensions that are structurally sounder than thinner roll-form aluminum.
Not only does metal's superior strength result in thinner frames but these frames can be made larger while maintaining strength. Whenever you see expansive picture windows in high-end homes, most likely these will be aluminum frame windows.
For example, Fleetwood's Series 3070 window is a massive 18' tall, yet its vertical sightline is only 2-1/8".
An aluminum window exterior does not necessarily mean that the entire frame is metal.
Some windows are aluminum-clad wood. Typically a soft wood such as Ponderosa pine gives the window both its structural strength and acts as a thermal break. The thin aluminum cladding protects against the elements.
Other windows are aluminum-framed. Aluminum provides structural strength to the window. Except for a few elements (notably the thermal break), the entire window frame is aluminum.
Frames are available thermally broken for colder climates or non-thermally broken for less harsh areas.
- Jeld-Wen's Premium Aluminum and Builders Aluminum
- Milgard's aluminum series windows
- Fleetwood entry-level or premium lines
Aluminum Windows Can Look Like Metal or Not
One allure of aluminum windows is its stark metallic look. This is achieved by a process called anodizing. Only a few colors are available. Aluminum can also be painted; this vastly increases the color choices.
Anodizing: Andersen, for example, produces seven anodized finish aluminum windows. Similar to stain penetrating wood, anodizing penetrates aluminum but does not cover it in the way that paint does. Sunlight will not affect anodized aluminum.
An anodized finish is a 0.05 to l.5 mils thick oxide film. According to Kaaren R. Staveteig of the National Park Services' (NPS) preservation team, anodization:
...is produced in an acid bath by passing an electric current through the aluminum. The thickness of the coating was determined by the strength of the current and the duration of the treatment. The coating could be clear or integrally colored by adding pigments or dyes before it was sealed. Anodizing increased the resistance of the metal to corrosion and wear.
Colors (Liquid Finish): Another treatment for aluminum is a liquid finish--a baked silicone polyester enamel paint.
For example, Andersen offers fifty liquid treatment colors. This paint is rated to match AAMA 2604 and 2605 (American Architectural Manufacturers Association) specifications, translated to between five and ten years of constant exposure in South Florida sun.
Best For Warmer Areas and Often Found Only There
Windows are already location-dependent; you just may not know it. A Pella dealer in Key West, FL can offer different windows than a Pella dealer in Buffalo, NY.
Traditionally, aluminum framed windows have been used in great numbers in mild or warm climates. They do not work as well in colder climates.
Even high volume window company Fleetwood admits that aluminum is "not as efficient as wood" in the manufacture of windows.
For another example, Jeld-Wen's Premium Atlantic Aluminum windows are readily available in Florida and available on order in southeast Texas and south Louisiana, Mississippi, Alabama, and Georgia. If you live outside of those areas, you cannot even purchase this window.
This means that if you live outside of warmer areas, you can still buy aluminum framed windows. The difference is that they will be the costlier premium or architectural style aluminum windows.
These windows are typically thermally broken by pouring liquid polyurethane into an extrusion pocket.
Exterior Materials That Are Lower Maintenance Than Other Windows
Most windows have exterior weathering issues, some more than others. Wood-exterior windows are notoriously difficult to maintain. Paint that adheres well to siding's flat surfaces adheres less well to the many angles of wood windows' frames, mullions, and muntins.
Even vinyl windows, with their "Vinyl Is Final" claim to fame, break down over the years. Darker color vinyl windows can lose their pigments and even the vinyl can warp.
Aluminum windows are as maintenance free as you can get in a window. It is no coincidence that commercial buildings heavily rely on aluminum-frame windows: owners want a "set it and forget it" window, not one that they need to replace every ten years.
Aluminum Can Corrode
Aluminum resists most weatherborne corrosive elements. But it does eventually deteriorate.
The protective oxide finish and the aluminum itself will break down under the force of air-borne abrasives, such as dirt and sand, according to the NPS's Staveteig. Even extended periods of high humidity can break down the protective finishes.
Outside of weather-borne elements, aluminum windows can also be affected by:
- Wet concrete, mortar, and plaster
- Acid-based chemicals used to clean masonry
- Other metals like copper or steel when galvanic action is present
Harder To Find Replacement Aluminum Windows
It will be more difficult for you to find an aluminum replacement window than new-construction window.
New-construction accounts for 17.5% of aluminum windows sold versus a meager 2.5% replacement windows.