This course is part of the Multifamily Housing Academy

ALUMINUM PLUS COATINGS FOR ENHANCED PERFORMANCE

As the previous section detailed, the inherent physical attributes of aluminum make it the ideal choice when specifying trim packages for multifamily projects. In particular, its strength and durability are enhanced by the extrusion process, which creates an oxide film on the surface that naturally prevents corrosion. These benefits can be expanded even further when coatings and finishes are included in the speci47fication process.

There are several coatings and finishes available for extruded aluminum trim, including powder coatings, liquid paints, and anodized finishes. It is critical that architects understand and convey to project owners how these coatings can impact the aesthetics, performance, durability, and cost of the extruded aluminum trim. Let’s take a closer look at each of these.

Powder Coatings

Powder coating is a dry finishing process that is used in many industrial applications. Powder coating is a popular choice for finishing extruded aluminum trim, and for good reason: the process creates a high-quality finish that’s resistant to scratching, chipping, corrosion, and fading. It’s also available in a plethora of color options. A basic understanding of the powder coating process reveals why it results in such a resilient finish.

Photo courtesy of Tamlyn

Another angle of the first layer of powder being applied to the profile before eventually being tossed in the oven to cure.

Powder coatings start with a polymer resin blended with curatives, pigments, leveling agents, modifiers, and other additives. These ingredients are melted together, mixed, cooled, and ground into a powder which is applied to the aluminum substrate using a spray gun—a process called electrostatic spray deposition. (Alternatively, powder coatings may be applied using a fluidized bed application. Here, preheated parts are dipped in a hopper of fluidizing powder, and the coating melts and flows over the substrate.) As the substrate is heat cured, the coating chemically reacts with the aluminum, creating long and strong molecular chains that are very difficult to break down. The resulting coating is more durable than liquid paints, which can degrade as they are exposed to weather, temperature extremes, and UV light.

Then there are the aesthetics. Not only are a plethora of color options possible, but coatings that start with high-quality powder tend to be remarkably consistent. It’s easy to match colors, and recent technological advances have enabled new looks, such as matte and chrome finishes.

Liquid Paint

Ever popular and familiar, liquid paint is available in more colors than just about any other finish option. Several types are appropriate for use on extruded aluminum, including acrylics, polyesters, silicone polyesters, and PVDF. Because liquid paint can be custom-mixed for each job, however large or small, it offers great flexibility; however, it does have a few key drawbacks when compared to powder coating. The first concerns its sustainability and environmental health. Some liquid paints contain volatile organic compounds, or VOCs, which have been shown to harm human health and the environment. The paint is typically spray-applied, and some of the product inevitably goes to waste. In addition, a painted finish may not be as consistent as a powder-coated finish.

Photo courtesy of Tamlyn

Liquid paint can be custom-mixed for each job and offers great flexibility in final finish.

Anodized Finishes

Anodizing is a controlled electrochemical process that deposits an oxide film on the surface of the aluminum trim. The resulting finish is decorative, durable, and more corrosion resistant than the untreated substrate. The process is accomplished by dipping aluminum into an acid electrolyte bath and passing an electric current through the medium. The process allows aluminum oxide to fully integrate into the substrate of the product. Although anodizing helps guard against corrosion, it does not increase the strength of the aluminum itself.

Anodizing creates a shiny, dynamic surface with an undeniably modern aesthetic. It is available in a clear finish or limited color selection such as bronze, gold, and black. Note that trim with an anodized finish may vary slightly from piece to piece; a design utilizing such trim should account for this natural variation.

The anodizing process creates a more porous surface that can receive paint; in fact, when color is applied, the dyes are locked into the substrate and will not peel or fade when exposed to sunlight.

Some companies have started to skip the traditional anodizing process and are instead opting for a powder coating that imparts an anodized sheen. The coating is available in several popular colors, including dark bronze, medium bronze, light bronze, gold, and black. Powder coating is faster and less involved than anodizing; it is also ideal for smaller projects since it can accommodate smaller batches than anodizing.

SUSTAINABLE FROM START TO FINISH

Aluminum is naturally sustainable. Thanks to aluminum’s inherent strength and durability, products made from this material will last decades before they need to be replaced and recycled. Because it is so lightweight, it is also less expensive to transport than other architectural metals.

Aluminum does not off-gas, and manufacturing or recycling it does not create hazardous waste. It is a good material choice for project teams seeking to achieve LEED or WELL certification, or to meet the stringent requirements of the Living Building Challenge (LBC), as it does not appear on the Red List, an inventory of “worst-in-class” materials, chemicals, and elements known to pose serious risks to both human health and the environment.

Aluminum is the only material that more than pays for the cost of its own collection. It is a completely recyclable material that does not degrade with reuse. Once the material is produced, it can be recycled indefinitely. In fact, approximately 75 percent of all aluminum ever produced is still in use today. This is especially significant when you consider the carbon emissions required to manufacture new aluminum. Recycled aluminum saves more than 90 percent of the energy costs needed for primary production, and it generates just 8 percent of the emissions.

The consequences of aluminum recycling are profound, saving not just energy and greenhouse gases, but other resources, too. Every year aluminum recycling saves approximately 70 million barrels of crude oil, 45 million tons of fresh and sea water, 7.5 million tons of solid waste, and 27 million tons of CO₂.

The Benefits of Sustainable Buildings

Extruded aluminum trim products can help support sustainable building goals and can help projects achieve certification under several popular green building programs. Increasingly, green buildings are becoming the norm in new construction. This is thanks in part to ever more stringent building codes, but also because of leadership at the federal, state, and local level. The US government, for example, had mandated that all new federal building be net-zero energy by 2045. The state of California has required new state buildings to be built to LEED standards since 2004, and Massachusetts recently mandated that large non-residential buildings achieve net-zero energy by 2035.

More and more project owners are realizing that “green” buildings come with a multitude of benefits: they save money over the long term, as they use much less energy than conventional buildings. As we learned earlier, they also save resources and money by promoting products, materials and systems with long-term value, which don’t require as much maintenance and don’t have to be replaced as often. These buildings also promote the health and well-being of occupants—a chief concern for multifamily project owners, as residents who are happy in their dwelling units are likely to stay longer. Green buildings are also likely to be more resilient, which means they buffer occupants from extreme weather and temperatures, and are more likely to remain functional during disasters.

In fact, sustainable features can give multifamily projects a competitive edge, especially among younger residents, who increasingly value health and wellness, and who are deeply concerned about climate change and environmental degradation. Certification under one or more green building programs can signal to potential residents that a multifamily project was designed and built in an environmentally responsible way, and that the units are healthy, comfortable, and energy efficient. In addition, more multifamily real estate investors are adopting environmental, social, and governance criteria for their investments, in part because green buildings yield better returns.

Photo courtesy of Tamlyn

Anodizing creates a shiny, dynamic surface with an undeniably modern aesthetic. It is available in a clear finish or limited color selection such as bronze, gold, and black. The close-up image on the right shows the finished texture which helps lock in the dyes into the substrate for enhanced durability when exposed to sunlight.