Extruded vs Roll-Form Aluminum: Why it Matters on Windows

CLAD WINDOWS

Clad windows simply refers to the different materials “capping” the wood window so that it becomes more durable and less likely to rot. Many window manufactures design a wood interior, clad exterior window. Often times there are interior wood specie options as well as different exterior cladding choices such as vinyl, fiberglass and aluminum. I will be focusing on an aluminum clad exterior in this post. There are a number of aluminum clad wood windows on the market and they are not all created equally. 

When comparing various manufacturers to one another, it is important to understand the differences in materials and construction that windows are made out of. The aluminum exterior is made in one of two ways: roll form or extruded.

HOW THEY ARE MADE

ROLL FORM

The roll forming process uses a pair of rolls to fabricate the metal. Metal sheets are passed through the rolls several times until the desired shape or profile is achieved.

EXTRUDED

The extruded aluminum process produces components by pushing the metal through a die or mold of the desired cross-section.

So which is better you may ask? Well let me tell you more about the differences in relation to the cladding on a window.

DIFFERENCES

The roll form uses less material and is thinner… think of a roll of aluminum foil, or about the thickness of soda can. The roll is wrapped around the exterior or the window to become the cladding. Since it’s so thin, the material is more susceptible to dents. The joints at lapped (one on top of another - or overlapping) which is less attractive and  makes them prone to water/moisture intrusion. Lastly, the finish on roll formed product is less durable which means it will fade and chalk earlier on - when compared to the extruded painted finish. 

ROLL FORM ALUMINUM CLAD WINDOW

Extruded aluminum ends up being about the thickness of a quarter - MUCH thicker. Because of this extra thickness, it is obviously stronger and more durable, so harder to dent or damage. The finish on extruded aluminum is of higher quality (a lot of manufactures use a Kynar painted finish) which makes them less prone to fading or chalking over time. Lastly, the joints are either mitered or butt jointed which are more pleasing to the eye + are more tightly sealed against moisture intrusion. 

EXTRUDED ALUMINUM CLAD WINDOW

EXAMPLE OF MATERIAL THICKNESS

FINISH

AMMA, American Architectural Manufacturers Association, is one organization that test windows and doors.  Their standards for finished aluminum cover three different categories: AAMA2605, AAMA2604, and AAMA2603. 

2605 is the most stringent standard and normally includes 70% Kynar paint or 70% PVDF paint.  2604 is the middle standard and typically uses a 50% Kynar Paint.  The 2603 specification is normally met using a baked on enamel and is the lowest grade finish level in the standards.  Kynar is a resin inside the paint that is applied to the aluminum extrusion. Any house or window in a coastal environment, or exposed to a lot of UV or sunlight, 2605 will be your best choice for longevity and durability.

20 year old roll form aluminum

20 year old roll form aluminum

Conclusion

So back to the question, which is better? If you read my points above, the clear answer is extruded aluminum clad windows. They are more durable, more attractive and offer a superior painted finish. If you are shopping for windows with an aluminum clad exterior MAKE SURE IT IS AN EXTRUDED ALUMINUM, otherwise you’ll regret it down the road.