Aluminum vs. Other Materials in Commercial Window Applications
There’s a growing trend towards using vinyl, wood and fiberglass/composite products in commercial applications. Reasons range from seeming to be less costly or the promise of higher u-values, to appearing to come with a “lifetime” warranty. This reasoning is, in many cases, misguided.
Cost Savings – Everyone must be concerned about cost. It can make or break a project. However, consider this… are you paying less now for a product that will need to be replaced in half the time as an aluminum product will?
Thermal Protection – High u-values can protect occupants from feeling extremes in weather in their home, and can save them money on heating and cooling costs. But will the money saved be negated in the future by the cost to replace the products over the next 10-15 years? Are the values being considered appropriate for the project? The IECC (International Energy Conservation Code) has two versions: Residential and Commercial. Is the right version being applied?
Warranty Coverage – The idea of a “Lifetime” warranty is very comforting, but what is a “lifetime” to a manufacturer vs. an owner? Any reputable manufacturer makes adjustments to their warranty if a product is being used in a commercial project. Read the entire warranty; most are available online. What are the details of what is covered under their commercial warranty? Be sure to dig deep and really find out the details… do these warranties cover your commercial, multi-storied, non-owner occupied dwelling?
Specifying and installing a product that will clearly address the unique performance needs of a project is critical. Developers and designers whose buildings are intended to have an extended lifetime and especially those expected to be subjected to rigorous use, should be considering the distinct and proven advantages of aluminum.
Sustainability – Aluminum windows are comprised of a very high percentage of recycled content, and can be recycled over and over again without loss of properties. It is estimated that over 65% of aluminum used in fenestration is still in use. (Source: AAMA 2009)
The high intrinsic value of aluminum scrap makes recycling economically attractive. Using today’s technology, aluminum and its alloys are re-melted and reused without any loss in quality. Besides, aluminum recycling requires much less energy than the production of primary aluminum from its ore. Thus, recycling is a cornerstone of the sustainability of most aluminum products, saving both raw materials and energy while also reducing demands on landfill sites.
LIFE CYCLE PERFORMANCE OF ALUMINIUM APPLICATIONS
International Journal of Life Cycle Assessment, May 2009, Volume 14, Issue 1
Strength – The mechanical properties of aluminum exceed that of vinyl, wood and fiberglass/composite by multiple times, allowing it to be manipulated (rolled or extruded for example) without reducing performance.
Aluminum is one of the lightest engineering metals, having a strength to weight ratio superior to steel. (UK multi-metals material manufacturer Aalco®, pub. 2005)
Performance – AAMA ratings were established universally, for ALL materials. Aluminum products are demonstrated to easily achieve the highest AAMA Performance Grades including AW, HC (now obsolete AAMA 2005) and CW, where vinyl is typically restricted to lower grades of C (now obsolete AAMA 2005), LC and R.
Testing Method – The AAMA testing model incorporates a required minimum test size known as the Gateway Size. Aluminum/metal can achieve higher grades required for AW and CW (highest ratings) at the Gateway Size. Consequently, it is common to see Design Pressure only (DP; a number only) without reference to any specific AAMA performance class. This results in a product that meets one criteria of an AAMA class, but not all the others such as air infiltration, water penetration and limits on deflection, as well as other aspects.
Design Flexibility – Aluminum has the distinct advantage over vinyl, wood and fiberglass/composite of being receptive to various types of finishes including paint, fluorpolymer-based and anodic coatings. These add to the longevity and permanence of aluminum products. By contrast, some of these finishes are not available on vinyl, wood and/or fiberglass/composite
Degradation of Material – As a more stable material, aluminum is unaffected structurally by the elements and UV rays, and will far outlast vinyl, wood and fiberglass/composite. The stability of aluminum is also evident when comparing the rate of expansion and contraction of these materials. Vinyl will expand and contract in warmer and colder environments at a rate of over 3 times that of aluminum. Wood is susceptable to decay and insect infestation. High expansion/contraction rates and degradation from decay allow for the risk of premature glass failure, hardware failure, and failure of other components.
From UV to infra-red, aluminum is an excellent reflector of radiant energy. Visible light reflectivity of around 80% means it is widely used in light fixtures. The same properties of reflectivity makes aluminum ideal as an insulating material to protect against the sun’s rays in summer, while insulating against heat loss in winter.
Aluminium - Specifications, Properties, Classifications and Classes, pub. 5/17/05
UK multi-metals material manufacturer Aalco®
It is important to consider the total cost of a building over its entire intended lifecycle, rather than just cost at the time of development when addressing the issue of energy efficiency. While installing windows with a slightly better initial U-Value can provide cost savings, the owner sacrifices other performance factors and sets the stage for the need to replace windows and doors long before the building’s lifecycle budget intended. Using a quality, thermally broken aluminum unit from the start will give the owner a product that is energy efficient, strong and long-lasting.
There are certainly advantages of using non-aluminum windows and doors, but only in the proper setting and context. Arguably, a truly commercial project is not the proper setting for vinyl, wood and fiberglass/composite.
Understandably, many prefer vinyl, wood, fiberblass/composite or other products for their aesthetics. However, in commercial applications, the “Best Value” based on true initial cost, energy efficiency, overall performance and true total building or project lifecycle cost, rests heavily in favor of aluminum.