Environmental responsibility has been an increasingly sought-after attribute of new building construction and renovations. This has driven and had been driven by the development of Leadership in Energy and Environmental Design (LEED) certification by the U.S. Green Building Council. LEED is a rating system; points are awarded for design elements that reduce the environmental impact of the building. There is even a rating system for homes as a result of the demand for green building practices in new homes.
A tangible way of decreasing the environmental impact of a building is to use sustainable materials in its construction. This is important, in part because of the amount of material and potential waste that goes into a new building. According to the Environmental Protection Agency, in 2015 the waste stream generated by construction and demolition was twice as large by weight as that from municipal solid waste. When materials that can be recycled or are derived from recycled materials are used in construction, the amount of waste associated with the building going into landfills is reduced.
Perhaps the most important reason to use sustainable materials is to create demand for sustainable materials. This is evident from recent disruptions to the markets for recyclable materials. You might have heard about the fallout from to regulatory changes in China that severely limit the types and qualities of waste material that China will accept as imports. Demand for plastics marked for recycling as No. 3 through No. 7 and mixed paper has been especially hard-hit.
The fundamental problem is that to keep recyclable waste out of landfills, it has to be separated from other waste streams. This usually means active participation of consumers and business in collecting – something that can be challenging in an increasingly throw-away society. For a recyclable material to be marketable at the wholesale level, it must be available in quantity and sufficiently free of contaminants as to be easily incorporated in new products. This is labor intensive and requires costly logistics. For multi-sort recycling, the labor is provided for free by the user, but at the expense of lower participation, increased collection costs and a high error rate. Single-sort recycling requires capital-intensive sorting facilities with paid labor and may be unable to sort materials sufficiently to prevent downcycling, especially of paper and plastic. The market value of a recyclable material must be maintained at a level where it pays to collect and process the material. This requires a sustained demand for the material. Incorporating recycled material into building projects is one way to drive that demand.
Perhaps the easiest way to use recycled material in a building project is to start with an existing building. Using as much of the existing building fabric as possible reduces the need for new materials and keeps existing material out of landfills. Construction codes are generally permissive about renovating existing buildings. Typically existing construction does not need to fully conform with modern codes unless changes in loads or occupancy exceed certain limits or specific hazards have to be mitigated. Using an existing dwelling as a home is pretty straightforward, but sometimes with some creativity, you can modify an existing building for something else. This is called adaptive reuse and is common in commercial projects. In the interest of historic preservation, cities are increasingly renovating historically significant buildings to meet current demands. In some cases, buildings have been moved or disassembled and reassembled elsewhere to preserve them.
For fully new construction, the most direct and intuitive way to recycle materials for your project is to use salvaged (sometimes marketed as reclaimed) materials. This can be easier said than done, however. All new construction must comply with modern construction codes. Salvaged material may not comply with modern standards for strength, fire prevention or energy efficiency. For example, modern wood construction is specified based on the species of wood and grading rules; these rules did not exist 100 years ago and salvaged timbers may not comply. There are ways around the code compliance problem. Design professionals can sometimes develop alternative acceptance criteria by means of analysis or testing. In the case of reclaimed timber, modern grading can be applied or historical methods of analysis and design can be used. Another approach is to use salvaged material as finishes or furnishings that are not subject to same code requirements. However, some materials, such as certain electrical and mechanical components cannot be reused because they cannot be reinstalled per code.
It is unlikely that a new building can be built completely of salvaged material. However, a variety of new building materials are available that use recycled content in their manufacturing process. For recycled content, steel is an excellent choice. Structural steel produced in the United States contains about 93 percent recycled content on average. While it is uncommon to frame a residential structure entirely with structural steel, it is not uncommon to use isolated steel beams and columns where open floor plans and large windows make convention wood construction impractical. Light gauge steel that is commonly used for light framing contains at least 25 percent recycled content. Steel building materials can be recycled without downcycling and structural steel can be disassembled and reused, further reducing the lifecycle environmental impact of steel products.
Like structural steel, the reinforcing steel used in concrete and masonry is almost entirely made from recycled steel. Recycled concrete can be used to replace a portion of the coarse aggregate in new concrete. Recycled plastic and glass have been used as aggregate in non-structural applications, often for aesthetic purposes. In addition, research has been performed on using aggregate made from recycled plastic in a variety of concrete products, although it is not yet commercially common. Some of the Portland cement in the concrete can be replaced by industrial by-products that improve the durability and often the strength of the concrete mix.
There are now numerous manufacturers of synthetic dimensional lumber and decking that are made with recycled plastic and wood by-products. These materials have been commonly used for outdoor decking and stairs, as a low-maintenance alternative to wood. Structural plastic lumber is available and has comparable properties to structural composite lumber. However, it is more expensive than wood and code provisions have not caught up to facilitate its use in buildings.
Reusing and recycling building materials or whole buildings is a good way to reduce the environmental impact of residential construction projects. However, it is not the only way. Some new materials are made sustainably or can reduce the lifecycle environmental impact of the building. Using recycled materials in a project has the added benefit of creating demand for recyclables. Providing a stable market for recyclables is crucial to reducing waste, whether from construction or consumers, going into landfills.
The information and statements in this document are for information purposes only and do not comprise the professional advice of the author or create a professional relationship between reader and author.