Sustainable building materials contribute to healthier environments and a greener future.
Sustainable building materials are essential for greener buildings—and a healthier world. Construction and demolition waste makes up about 40% of the total solid waste stream in the U.S. and about 25% of the total waste stream in the European Union, according to USGBC. Sustainable building materials can help us reduce this large amount of waste and the negative effects of greenhouse gases.
You have to look at the big picture when you consider the impact of a building—the building’s life cycle. The American Institute of Architects’ Guide to Building Life Cycle Assessment in Practice discusses how to evaluate the potential environmental impacts for every stage of a building's life. One important factor in the building’s life cycle is selecting sustainable building materials. Architects need to consider how building materials are sourced, manufactured, transported, used, and discarded during construction. Every detail matters.
LIFE CYCLE ASSESSMENT
Sustainable materials management is a systematic method of using and reusing materials more productively over their full life cycles. Global consumption of materials has quickly risen over the last century. This has resulted in habitat destruction, biodiversity loss, and desertification, according to the EPA. Materials management is linked to an estimated 42% of total U.S. greenhouse gas emissions. This is why we need to adopt more sustainable ways to manage materials, for the sake of Earth.
The Smart Surfaces Coalition is promoting cost-effective sustainable material solutions, including cool roofs, permeable pavement, green roofs, and solar panels. More than 20 leading sustainability organizations, including the USGBC, formed the coalition. “The Smart Surfaces Coalition shows cities how to use advanced surface technologies to reduce heat and prevent flooding,” says Greg Kats, the coalition’s founder. “These solutions deliver enormous health and financial benefits, slowing global warming, enhancing quality of life, and saving taxpayers billions of dollars in energy costs.”
The USGBC reports that implementing smart surfaces will help U.S. cities cut excess heat days by half, save $700 billion, and create 270,000 jobs. Sustainable surfaces also reduce flooding and combat the urban heat island effect. The Smart Surfaces Coalition is already working with a dozen cities to provide training and resources to city officials. “Cities are increasingly at risk from severe summer heat,” Kats says. “This coalition will support adoption of smart surface technologies to save billions of dollars and cut greenhouse gases while making cities cooler, more resilient, healthier, and equitable.”
The societal and environmental benefits to implementing sustainable building materials in projects is undeniable. The most sustainable building materials have a lower environmental impact, like reused or recycled materials. Green building materials are durable and require less energy to manufacture. They don’t deplete scarce resources and can be locally sourced to reduce transportation emissions. Let’s take a look at five sustainable building materials that are making waves in the industry.
1. Precast Concrete
Concrete is one of the most common building materials in the world because of its durability and strength, but precast concrete is proving itself to be one of the most sustainable building materials. Precast concrete is produced in a controlled manufacturing plant and then transported to a site already reinforced and finished according to specification, which eliminates the need to cast concrete on-site and shortens the installation time. This makes precast concrete building less disruptive to the site environment, producing less construction debris, dust, noise, and pollution.
The materials used in precast concrete can be locally sourced, including the cement, the coarse and fine aggregates, and the steel, which reduces shipping waste and overall carbon footprint. Precast concrete units can be disassembled in an existing structure to be moved or reconfigured, and the concrete can be crushed and reused as aggregate. Fabcon Precast, a leader in the precast concrete industry, uses a combination of concrete and EPS foam that maximizes the foam in the concrete piece—increasing insulation capabilities.
Regular concrete usually has a thermal resistance rating of about 0.11 per inch of thickness, while precast concrete can provide double the resistance—0.22 per inch of thickness. Precast concrete can be dense or lightweight, giving builders options when deciding on the level of thermal insulation needed. Concrete itself is an effective fire barrier. Precast concrete wall panels are capable of providing a two- to four-hour fire rating. And they stay intact even in hot chemical fires. Precast is also resistant to rain penetration and wind-blown debris, offering protection from storms and harsh weather.
The light color of precast concrete reflects more sunlight and heat than dark surfaces, reducing the “urban heat island” effect and cutting air conditioning costs. You can potentially save millions of dollars in energy costs per year. New buildings with precast concrete structures can also earn up to 23 LEED certification points, according to the Little Green Book of Concrete, published by the National Precast Concrete Association.
2. Cross-Laminated Timber
Alternatives to concrete, like cross-laminated timber, are also increasingly popular. While wood has been used in construction since the beginning of time, CLT has joined the ranks of the most sustainable building materials. Relatively new to the U.S. building market, CLT is a solid wood panel made from layering boards in alternating directions, bonded together with structural adhesive.
The alternating fibers and solid composition of CLT give it the potential to substantially reduce the carbon footprint of new buildings by replacing structural concrete. It’s lightweight, strong, and fire and earthquake resistant. Dalston Works—the world’s largest building constructed out of CLT—weighs approximately one-fifth of a concrete building of the same size. And on top of that, it was completed an estimated eight months faster than if traditional building materials had been used.
All CLT components of Dalston Works were prefabricated and then transported to the construction site, including floors, walls, stairs, and shafts. This improved the work environment onsite, meaning less noise, dust, and waste. Using prefabricated CLT components, construction workers could put up a whole floor in a week, allowing CLT projects to be built larger and faster.
In order to maintain wood resources, the timber is sourced from sustainably managed forests. One of the most important environmental benefits of using CLT is its carbon sequestration properties that aid in climate change mitigation. It is estimated that roughly one cubic meter of wood stores around 1.10 tonnes of carbon dioxide, according to a study published by the Journal of Cleaner Production. Choosing CLT as one of your sustainable building materials also results in lower greenhouse gas emissions and lower energy input required to manufacture CLT panels.
3. Reclaimed Wood
Building with reclaimed wood prevents unnecessary logging and reduces manufacturing and transportation-related greenhouse gas emissions, according to the National Resource Defense Council. Reclaimed wood is a sustainable building alternative to harvesting new lumber.
Wood that was harvested and milled decades ago and that has been in use for years as barn siding, wood pallets, and railroad ties and trestles has been exposed to the elements, which increases its stability. Also, reclaimed wood is mostly dense-grain, old-growth material, so it’s stronger and more durable than new lumber from younger, less dense trees more prone to warping and bending.
Many reclaimed wood companies have taken root. Centennial Woods distributes weathered and reclaimed wood from snow fences in Wyoming to the construction industry. These braced wood fences are exposed to freezing winds in winter and blazing sun in summer and have a very low moisture content (4-6%).
The Singapore Green Building Council did a carbon impact study of the product and found that, even accounting for shipping across the Pacific Ocean, this weathered wood is carbon negative. The low moisture content of reclaimed wood eliminates the need for kilning and drying, which saves time and energy. The wood for the fences is sustainably harvested Douglas fir and Ponderosa pine.
Steel has been a popular choice for construction projects long before the green building movement began, but the industry is constantly adapting and advancing. Over the past 25 years, the steel industry in North America has reduced energy intensity and greenhouse gas emissions by more than a third, making the production of steel more sustainable and reducing its environmental impact. It’s often used in pools, drains, and even in steel conduit.
Steel helps builders and designers meet steel building codes and earn multiple credits for green building rating programs like LEED or the Living Building Challenge. This is because steel can be easily assembled and disassembled, making it surprisingly recyclable: Any steel product can be recycled into another. Virtually all steel products contain at least 25% recycled content already, with some products containing up to 100% recycled material.
Because of its recyclability, using steel reduces construction and demolition waste because many steel construction products are made off-site. They are pre-manufactured, pre-cut to finished size, or fabricated to precise project specifications before they are shipped to the job site. Steel scrap generated onsite can be easily recycled. In fact, 60 to 80 million tons of steel scrap are recycled into new North American products every year.
Steel is a flexible and strong green building material. It doesn’t expand or contract in the presence of moisture and it’s not vulnerable to pesky issues like termites. Steel can be easily disassembled and relocated and it is airtight, too. “Steel is dimensionally stable and, when properly designed, can provide an exceptionally tight building envelope, resulting in lower air losses and better HVAC performance over time. This helps to improve the overall energy profile of the building,” says Mark Thimons, vice president of sustainability for the Steel Market Development Institute. Steel roofing can also reduce the heat island effect by applying long-lasting coatings that offer optimal solar reflectance, achieving energy efficient heating and cooling.
Terrazzo is a mosaic style of flooring where small pieces of marble or granite are set in polished concrete or epoxy resin. With simple maintenance, these floors can last 40 years or more without losing their brilliance. Modeled after 20th century Italian work, original terrazzo was set in cement, but now 90% of terrazzo floors are made with an epoxy resin.
Terrazzo & Marble Supply Companies, a leading company in the terrazzo industry, makes what they call “forever floors.” The company manufactures its own epoxy that acts as a binder holding the chips together, allowing them to incorporate materials like aluminum, zinc, and brass, along with recycled products like glass, porcelain, marble, and even beer bottles as aggregate. “We take a lot of things that would be put into the waste stream that we can reclaim and reuse in a terrazzo floor,” says James Bateman, division manager of the company.
Terrazzo is poured in place, so there’s a lot of color and design flexibility, and the flooring is one seamless surface, which alleviates hygiene issues. These floors are very easy to clean and can be used in high-traffic areas like schools, stadiums, and airports.
Known for design flexibility and remarkable durability, using this sustainable building material may carry a higher upfront cost, but its durability and life expectancy often make it the most affordable option in the long run compared to life cycle costs for carpet, porcelain, or other flooring materials. A terrazzo floor might cost five times more than carpet, but Bateman says you will probably have to replace that carpet six times during the life of one terrazzo installation, making this classic floor a modern sustainable building material.