Fluid Matters: The Water Footprint of Building Materials

Introduction

The environmental ecology of materials in building design and construction practices encompasses complex layers of information. Practitioners are enabled to partially assess material selection with the expanding toolsets and methods for life cycle analysis (LCA) (Hunt, Franklin, & Hunt, 1996), ecological footprint (EF) (Wackernagel, 1996), and carbon emission impacts. However, the data required for inputs in such calculation tools and methods is not always readily available or may require detail-oriented research that is non-billable in standard Architecture, Engineering, and Construction (AEC) practice. Professional organizations, non-profits, product manufacturers, and research practices are beginning to accumulate numerous modes for qualifying the accountability of building materials in terms of environmental impact characteristics through labeling mechanisms and certification practices. Yet, there is still an intuitive challenge in the design process to comprehend the intersection between the accumulation index of total building composition environmental impact with the ever-expanding and vast field of products and building materials offered on the market. While the challenges to addressing the environmental accountability of building materials are handled in part with labeling, (providing information on chemistry and embodied energy), the full comprehension of environmental impact is less known.

In particular, the water quantity and water quality impacts of building materials are not readily documented with accessible data sets, although they can be (Simonen, 2014). Furthermore, the holistic assessment of water impacts through interactions with building materials during operation and maintenance as a result of the building design characteristics cannot currently be traced directly into environmental contexts. Though we have basic calculation methods for obtaining water consumption impacts associated with building operations (i.e., due to source energy production, water use patterns, and wastewater treatment energy), we do not yet have integrated calculation methods for attributing the water consumption and quality impacts resulting from material sourcing and extraction, manufacturing, construction, and operational design standpoints. These aspects may be attainable in isolation, or readily available in high consumption industries such as food, fashion, and electronics, but are not yet apparent in a clear pathway format for AEC practitioners. The Water Footprint Assessment (WFA) method has evolved in other sectors over the past fifteen years or so (Hoekstra, 2017), but is not yet fully translated into the building material industry.

Beginning with the fundamentals of water physio-chemistry and the built environment, this chapter addresses the primary material groups (natural materials, non-technical ceramics, technical ceramics, metals, and polymers, elastomers and foams) through both water quantity and water quality interaction measures. With a specific lens of water impacts, the scope covers aspects of material sourcing and extraction, manufacturing and production, construction and installation, maintenance and operation, and end-of-life deconstruction and recycling. The results indicate a holistic water footprint metric for building materials (WF_BM). While there are numerous gaps in aspects of embodied water impacts for specific building materials, the research to date indicates a scale of impact for metals on the high end, to technical ceramics (glass), non-technical ceramics (concrete, masonry, stone), and polymers at the low end, with natural materials in the mid-range. Composites vary depending upon the material compositions and fabrication processes. Furthermore, a general correlation between energy footprint and water footprint can be made, indicating a proportional relation. A distinction is also made for water stress measures between water withdrawal from surface or groundwater and water consumed in the building material production process. The latter is no longer available for the replenishment of water resources.