This phase includes the impacts of using the product over its expected service lifetime, including any maintenance that is expected and required. PCRs and EPDs define the expected service lifetime of the product under consideration. For bricks, a reasonable service lifetime is 80 years. Tuck-pointing (i.e. repair) of mortar could be expected once during this service lifetime. The definition of the service lifetime is helpful when EPD users want to compare durability and longevity of different products in the same category. For example, an asphalt pavement does not have as long a service lifetime as its concrete counterpart, and users can take this into account (in the context of other variables) when specifying products.
This phase includes the impact of a product’s deconstruction and final disposition. Where recycling occurs, this phase includes the impacts of recycling a product, both positive and negative. For example, crushing a brick wall and recycling it into sub-base for roads might have a net decrease in carbon impact (because virgin aggregate does not need to be quarried for the road sub-base) and a net increase in energy impact (because the energy required to crush the brick wall is part of this phase).
A product category rule (PCR) is the standardized method for conducting and reporting an LCA. The PCR ensures all products in a certain category (e.g. ready-mix concrete or roofing products) are measured the same way and environmental impacts are quantified in the same way in each lifecycle phase. The PCR defines boundaries for measurement—such as cradle-to-gate or cradle-to-grave—as well as the functional unit measured (e.g. 1 m3 of concrete, or 1 square of roofing material). (The measurement of 1 square of roofing material is equivalent to 9.3 m2 [100 sf].)
PCRs are developed by industry experts and stakeholders using a consensus-based, collaborative, transparent process. They are then verified by an expert review panel. The entire process must follow guidelines generally laid out in ISO 21930, Sustainability in Building Construction–Environmental Declaration of Building Products.
PCRs are costly and, as a result, there is not currently a large number of them. However, this is starting to change, and more are being developed each year. For example, the Institute for the Market Transformation to Sustainability (MTS) has developed a unique universal ISO-compliant PCR that can apply to any environmentally preferable product. It was rigorously developed by independent third-party LCA experts and open to a public comment period. The only variable in MTS’ PCR is the functional unit, which must be defined for each product. MTS administers Sustainable Materials Rating Technology (SMaRT), which is the leadership sustainable products standard. MTS also acts as the program operator for SMaRT EPDs, which follow the SMaRT PCR.
An environmental product declaration is a document created by the manufacturer to show results of a lifecycle assessment. It is verified by an expert and approved by a program operator, such as UL Environment (ULE) or the aforementioned MTS.
EPDs that comply with ISO 14025, Environmental Labels and Declarations–Type III Environmental Declarations: Principles and Procedures, enable stakeholders to make direct accurate comparisons of some environmental attributes—such as carbon footprint and embodied energy—of similar products. This enables stakeholders to assess products with the same traditional attributes (e.g. strength, durability, cost) and choose the product with the lowest environmental impact of interest.
EPDs can have requirements for how often they must be renewed. For example, SMaRT EPDs used by this author’s firm must be renewed every three years. During the renewal process, aspects like energy input can be revisited and updated.
Impact categories describe the effect of a product lifecycle—or individual phases—on specific areas of concern. Impact categories include:
- global warming (also referred to as ‘carbon footprint’);
- fossil fuel depletion;
- metal depletion; and
- water depletion.
PCRs define which impact categories must be reported in each EPD. Of course, EPDs can always report more impact categories than required by the PCR. (For example, the SMaRT PCR also includes human health air pollutants, human toxicity, and eco-toxicity for air, soil, and water.) Design professionals and owners should consider which impact categories are of greatest interest for their projects. For instance, while carbon footprint is likely always a concern, impact on water resources might also be of particular consideration in the arid Southwest.
Boundaries are an important element in LCAs and associated EPDs. Simply put, where does the product system start and stop? Does the LCA consider the electricity used to power the plant and also the energy required to create that electricity? Does the EPD include cradle-to-grave impacts (i.e. all lifecycle phases) or only cradle-to-gate impacts (i.e. limited to raw material extraction and manufacturing phases, but not construction, use, or end-of-life phases)?
EPDs present results of the lifecycle assessment. It is necessary to understand which boundaries are used to accurately compare environmental data. Typically, EPDs show information with one of the following sets of boundaries (Figure 1):
- cradle-to-gate: considers raw material extraction, transportation, and manufacturing, including
- energy to create the plant’s operational energy;
- cradle-to-job: cradle-to-gate plus transportation to the jobsite; and
- cradle-to-grave: all lifecycle phases—cradle-to-job plus construction, use, and end-of-life.