DWM-logo.gif (6532 bytes)

November - December 2003

Aluminum

An Excellent 
Choice for Fenestration

by R.C. Goyal

Aluminum is used in aircraft because of its strength, lightweight material and rust-resistance; it is also used in the transportation industry to deliver household and commercial goods. Aluminum foil is used in our homes to prepare our meals and in cans to keep our drinks cool. Aluminum is used for automotive engines and body parts to minimize rust.

The same material is used for most commercial buildings. The tallest buildings in the world use aluminum facades in one form or another—whether it is for windows, curtainwalls, panels, storefronts, entrances or column covers, to name just a few applications. Aluminum has been—and continues to be—the choice material for fenestration in commercial construction. There are wide-ranging reasons for its use. 

A Brief History 
Charles Martin discovered the aluminum refining process in 1886. The material initially was extracted only at the rate of 50 pounds per day, but has grown considerably to meet the extensive market demands of today. The energy usage for extraction has been cut in half and more reductions will occur in the next decade. Since the material can be recycled repeatedly, and it takes considerably less energy for recycling, the energy usage to produce this material will be reduced exponentially as the rate of recycling continues to increase. 

The material was used extensively in World War I and II in non-fenestration applications. The first-known application of aluminum for fenestration occurred in 1927 in Pittsburgh and New York. The applications of this material for fenestration exploded after World War II. The expanded use of aluminum was made possible because an engineer applied structural steel as the load-bearing member of the building to replace brick and masonry. Aluminum curtainwall, storefront and windows emerged as the non-load bearing exterior cladding for buildings. 

As buildings started using more aluminum, the industry wanted to make the material less conductive to energy flow and condensation. The first applications of a thermal break to separate the exterior aluminum from the interior aluminum emerged in the 1950s. Many different types of thermal breaks have been used since then to respond to the Energy Policy Act of 1992 to reduce our dependence on energy and reduce emissions of greenhouse gases. It is fair to recognize that the aluminum industry addressed the concern for energy conservation long before the Energy Policy Act. 

Fast Stats

Though aluminum has a number of benefits, sales of aluminum products fall behind those of wood and vinyl, at least on the residential side. See the charts below to see where aluminum is headed in the coming years. 

                                                  Shipments of Prime Windows

                                                            1997 – 2006F
                                                          (Millions of Units)

New 
Construction 
1997 1998 1999 2000 2001 2002 2003F 2004F 2005F 2006F
Wood*
Aluminum
Vinyl
Other
Subtotal
11.8
3.8
7.4
0.3
23.3
12.4
3.7
8.9
0.5
25.5
13.2
4.0
9.6
0.4
27.2
12.8
3.7
9.0
0.4
25.8
13.1
3.0
9.6
0.5
26.2
13.7
3.0
10.4
0.6
27.7
13.5
2.9
10.6
0.8
27.7
13.6
2.8
10.9
1.0
28.3
13.6
2.7
11.3
1.1
28.3
13.6
2.7
11.5
1.3
29.2
Remodeling & Replacement 1997 1998 1999 2000 2001 2002 2003F 2004F 2005F 2006F
Wood*
Aluminum
Vinyl
Other
Subtotal
9.7
3.6
12.1
0.3
25.6
10.3
3.5
14.1
0.3
28.3
10.7
4.0
15.0
0.2
29.9
10.2
4.0
14.8
0.2
29.2
10.5
3.5
15.9
0.3
30.2
10.7
3.5
16.9
0.3
31.4
10.8
3.5
17.9
0.4
32.6
10.8
3.5
18.4
0.5
33.3
10.7
3.4
19.2
0.7
34.0
10.8
3.4
19.4
0.8
34.3
Total Construction 1997 1998 1999 2000 2001 2002 2003F 2004F 2005F 2006F
Wood*
Aluminum
Vinyl
Other
Subtotal
21.5
7.3
19.4
0.6
48.9
22.7
7.2
23.0
0.8
53.8
23.9
8.0
24.6
0.6
57.1
22.9
7.6
23.8
0.6
55.0
23.6
6.5
25.5
0.7
56.3
24.4
6.5
27.3
1.0
59.1
24.3
6.4
28.4
1.2
60.4
24.4
6.3
29.4
1.5
61.6
24.4
6.1
30.5
1.8
62.8
24.4
6.1
30.9
2.1
63.4

*Includes vinyl-clad and metal-clad wood units.
Source: Ducker Research Co. Inc.


Unfair Attacks
In the last decade or so, aluminum has been attacked unfairly. Some reports skew the performance of aluminum fenestration by using data from non-thermally broken aluminum frames with single glazing, while overlooking aluminum’s structural integrity and ability to provide a deflection limit at L/175.
Deflection limits have always been a part of AAMA standards for windows and doors. The members of AAMA currently are studying the deflection limit requirement and will include revisions to the next editions of their standards based on the results of this research. The American Institute of Architects and Construction Specification Institute master specifications currently mandate the aforementioned L/175 deflection limit for commercial fenestration products. 

It is true that competing materials such as PVC, wood, fiberglass, etc., are less conductive and provide higher thermal performance. The difference, however, is much smaller when using the current technology for thermal breaks in aluminum frames. The point to be made here is that U- values can be improved in any material by using spectrally-selective glass and low-E coatings to meet today’s energy codes. Aluminum can be energy-efficient while maintaining its structural integrity.

Aluminum does not warp at high temperatures nor does it shrink and become brittle at freezing temperatures or after the moisture content evaporates. Warping and shrinkage can cause excessive air infiltration, degrading the fenestration performance. The National Fenestration Rating Council (NFRC) tests for air infiltration, but U-factor is determined by testing a sealed window. NFRC is investigating the durability of windows at high and low temperatures to monitor air leakage and product wear for long-term energy performance. Aluminum is expected to perform well in both these areas. AAMA and NFRC will consider both of these tests for ultimate thermal performance of fenestration products.
There are other attributes that make aluminum an excellent choice for fenestration such as its ability to accept a variety of colors and finishes (anodizing and paints). This material can be extruded into very simple or complex shapes to complement the aesthetics required for building projects. 

Aluminum products also continue to be popular with many homeowners, builders and multifamily housing developers. The reasons for their popularity vary from region to region. When windows are larger in size or designed for sound insulation in homes at airports or a larger color selection is preferred, aluminum is the material of choice. They are also being used in residential applications for hurricane impact resistance. 

Aluminum Materials Council 
AAMA, being a material-neutral association, has provided the aluminum fenestration producers with a forum, known as the Aluminum Materials Council (AMC), in which to develop standards and promotional materials for aluminum. The AMC hopes to set the record straight about aluminum by providing technical information so architects, specification writers and end users can make informed decisions to select the appropriate fenestration material for each construction project.

As aluminum producers, we took the material for granted and did not market the benefits and sustainability of aluminum effectively. Competing materials were well-marketed while we were absent from the scene. In studying all of the various uses of aluminum and recognizing the advancements that have been made with the material in fenestration applications, I am pleased to be a part of the aluminum industry. Please join the efforts of the AAMA AMC to continue enhancing product performance and promoting the use of aluminum fenestration.


R.C. Goyal is the director of business development for Graham Architectural Products in York, Pa., and the immediate past first vice president of AAMA’s Aluminum Materials Council. 

DWM
© Copyright Key Communications Inc. All rights reserved. No reproduction of any type without expressed written permission.