Last Updated: Feb 24, 2022
After oxygen and silicon, aluminum is the most abundant element present in the earth's crust, making up well over eight percent of the crust by weight. While still a non-renewable resource, we will not be running out of aluminum any time soon. Starting about a century ago, architects realized that the strong but lightweight aluminum properties made it an excellent choice for large building projects. In 1931, large parts of the Empire State Building in New York were built with aluminum, including the famous spire that reached high into the New York skyline.
Today, aluminum is still regularly used for building skyscrapers, bridges, and other high-rises, multifamily apartment buildings. The London Aquatics Centre in the UK is another massive structure built mostly from aluminum. In individual homes, we find aluminum in the kitchen utensils that we use. And it can also be a significant part of our home construction. Below, we look at where we commonly find aluminum in our houses, the benefits, and the drawbacks.
Besides aluminum foil and pots and pans, many homeowners might have aluminum in their home's structural elements without ever knowing it. Aluminum is commonly used in metal roofing as a coating that helps preserve the underlying steel and increase roofing durability. Similarly, aluminum siding is also widely used for a low-cost external cladding option.
Older homes might also have some or all of their electrical wiring from aluminum. While aluminum doesn't boast a great deal of conductivity, like copper, it is lightweight, so many power lines are made from aluminum wires. Some homes contain windows and door frames made from aluminum, along with interior curtain walls. Also, some LED bulbs contain large amounts of aluminum in their manufacture.
The most oft-cited benefit of using aluminum for home construction is incredibly lightweight. Compared to other materials, aluminum has an exceptional strength-to-weight ratio and weighs up to 65 percent less than steel. For houses that use aluminum posts and beams, the structural element will be lighter without sacrificing strength and durability, especially compared to steel posts and beams. Aluminum allows homeowners to reduce their foundation's size and depth, thus potentially helping to reduce the volume of cement required for the home's foundation.
Aluminum is also resistant to corrosion. For this reason, it is sometimes used as a reflective and protective coating on steel roofing. One study found that coated aluminum roofs can reflect up to 95 percent of sunlight. This coating drastically improves the thermal performance of homes with a metal roof. It helps to reduce cooling loads during the summer months.
The fact that aluminum is ductile and malleable also allows architects and designers to be more creative in designing the structures they build. Unlike steel or other related metals, aluminum can be bent and curved to enable innovative home designs.
The most significant sustainable advantage of opting for constructing with aluminum is that, in theory, aluminum is 100 percent recyclable with no loss of its natural properties. Some estimates find that up to 75 percent of the almost one billion tons of aluminum mined from the earth's crust continues to be in use today.
Homes and larger buildings that use aluminum for structural elements, roofing, interior walls, or other features can obtain points toward LEED certification. Experts in recycling engineering at the Delft University of Technology in Europe have found that recycled between 95 and 98 percent of aluminum from demolished buildings. The energy to recycle scrap aluminum is only five percent of what it takes to produce new aluminum. This ease of processing makes aluminum an excellent choice for homeowners who want to lower their environmental impact by opting for recycled building materials.
There are two main drawbacks to using aluminum in your home. First, mining aluminum is a highly energy-intensive process that causes significant damage to the earth's ecosystems. We will take a closer look at aluminum mining below.
Secondly, relying on aluminum for certain aspects of your home can compromise acoustic performance, especially if you opt for aluminum siding. While aluminum siding is generally one of the most inexpensive exterior cladding options, it can be loud, especially during high winds or rainstorms. Also, aluminum is certainly not a "natural-looking" product. For homeowners wanting a more natural feel to their home, aluminum products will inevitably look like metal. Metal is often considered cold or industrial-looking, but it can be appealing to a modern aesthetic.
While aluminum is one of the most abundant elements found globally, it is never found "free" in nature. Technically, all aluminum on earth has combined with other elements to form compounds, two of the most common being potassium aluminum sulfate and aluminum oxide.
From a mining perspective, obtaining raw aluminum often requires massive strip mines. Strip mines have far-reaching environmental effects, including destroying forests, landscapes, and wildlife habitats. These mines also lead to soil erosion and the pollution of waterways. Once mined, the aluminum compounds need to be separated through electrolysis, which takes enormous electricity.
Newly produced aluminum has a high embodied energy footprint, measured by the "process energy requirement," or PER. PER is a measure of the amount of energy required to manufacture specific building materials. Since aluminum requires strip mining and energy-intensive processes to separate the aluminum through electrolysis, its PER is higher than virtually all other commonly used building materials.
According to studies done by the Australian government, aluminum products used in housing construction have a PER embodied energy rating of 170. This rating is the highest of all commonly used building materials. For comparison's sake, plywood has a 10.4 PER, while cement has a PER of 5.6. Even copper and synthetic rubber products have a significantly lower PER than aluminum, respectively, at 100 and 110 PER.
Aluminum from a recycled source contains less than 10 percent of aluminum's embodied energy manufactured from raw materials. When this is taken into account, aluminum's embodied energy footprint is much lower than concrete, plastics, and even masonry.
The most critical consideration is making sure that the aluminum is sourced from recycled materials when thinking about using aluminum. As we mentioned above, aluminum is one of the most oft-recycled building materials. So, using recycled aluminum will drastically lower the embodied energy footprint of your home to the point of helping you qualify for LEED credits. In most cases, the good news is that it is much cheaper for a supplier to find recycled sources of aluminum than to source it new. So if you are specifying aluminum for any part of your house, be sure to ask suppliers for their material's origins - and make sure it is recycled.
Helping to create demand for closed-loop recycled materials is an essential component of the circular economy. If this paradigm shift can take hold, there will be no such thing as "throwing away" something. To learn more about the circular economy, check out the Systemic Initiatives put forth by the Ellen MacArthur Foundation.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.