B-PATH: Quantifying the Impact of Structural Materials
A new software tool from scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) will help architects, engineers, and urban planners better assess and manage the environmental impacts of structural materials in commercial buildings.
The software tool, called the B-PATH model (Berkeley Lab Building Materials Pathways), allows designers and builders to estimate the energy, resources, and environmental impacts associated with the manufacture of structural materials; their effects on the energy use of a building during operation; and their impacts when the building is ultimately demolished and its constituent materials are reused, recycled, or disposed of. The Berkeley Lab's development of the B-PATH model was sponsored by the Portland Cement Association (PCA).
"Minimizing the environmental impacts of a building throughout its entire lifecycle is a promising way of reducing the energy use and greenhouse gas emissions of buildings," says Eric Masanet, the leader of the team that developed B-PATH. "The key is having a tool grounded in sound science to perform a lifecycle analysis—the data analysis and systems mass and energy balance modeling techniques to estimate the inputs of fuels, materials, and resources (and outputs of pollutants and waste) associated with all relevant processes in the lifecycle of a product or service."
In 2009, according to the U.S. Department of Energy, commercial buildings accounted for nearly 20 percent of U.S. primary energy use, more than one-third of U.S. electricity use, and about 15 percent of U.S. direct natural gas use. There are more than 4.6 million commercial buildings in the United States, with more than 64 billion square feet of floor space. According to a 2010 National Research Council report, the human health damages associated with the amounts of electricity and natural gas consumed by U.S. commercial buildings may be on the order of $20 billion per year.
The structure of a commercial building, such as its concrete or steel frame, uses a larger quantity of materials that require high energy per weight to manufacture than any other element of the building. A building design that uses the optimum amount of these building materials minimizes the energy required to manufacture them and helps to keep building costs down.
In the final phase of a building's lifecycle, demolition and materials removal, the B-PATH model can help determine how improved reuse and recycling can reduce the energy costs of the structural materials in new buildings. Using the correct structural materials to maximize reuse and recycling helps minimize energy use, because using recycled building materials requires less energy than manufacturing new materials.
B-PATH allows users to model the use of a range of typical structural building materials like concrete, steel, and lumber from their production, transportation, and construction until their end-of-life processes. Users can define which fuels and how much electricity is used in each of these processes, throughout the lifecycle.
The method B-PATH uses to calculate results is transparent and public, so that its users can understand how the calculations were made. Users can model variations in production pathways that occur as a result of supply-chain configurations, geographical locations of plants, plant technology vintages, fuel mixes, logistics, and other materials pathway characteristics that can be unique to local and regional supply chains. The model incorporates both current practice and best practice methods of manufacturing and construction to determine how they affect energy use. The user can tailor results to specific U.S. regions, which vary by climate, local and regional characteristics in materials supply chains, construction practices, and end-of-life pathways, as well as in the mix of fuels for electrical power supply sources and volume of water consumption.
Model results provide users with an estimate of a building materials' lifecycle energy use and greenhouse gas footprint. By modeling different scenarios, users can identify the optimal strategy to better reduce the energy use and long-term environmental effects of a commercial building before even breaking ground.
"Life Cycle Evaluation of Concrete Building Construction as a Strategy for Sustainable Cities," by Alexander Stadel, Petek Gursel, and Eric Masanet.
A copy of the report is also available through PCA [PDF].
The model is available as a download.