by Julie Rapoport, PhD, PE, LEED AP
When selecting products for a new project, architects, engineers, specifiers, and building owners consider many criteria, from aesthetics to strength to cost. Green buildings require an additional level of scrutiny to determine products’ environmental impacts in several categories, including operational and embodied energy, carbon footprint, and emissions.
Historically, evaluation of environmental impact relied on supplier claims, with some stakeholders researching specific aspects of a product’s composition and manufacture. Now, independently conducted lifecycle assessments (LCAs) and third-party-verified environmental product declarations (EPDs) are emerging as important tools for comparing some of the environmental attributes of similar products. (Another tool, Health Product Declarations [HPDs], which are recognized by the Leadership in Energy and Environmental Design [LEED] program, are even more nascent than EPDs. The topic will be worthy of an article in itself, once more of the initial groundwork has been completed and additional consensus achieved.)
With growing calls for increasing product transparency and the role it will likely play in U.S. Green Building Council’s (USGBC’s) newest version of Leadership in Energy and Environmental Design (LEED) due this summer, these resources are beginning to become mainstream for specification materials. LCAs and EPDs provide standardized methods for verifying manufacturers’ environmental claims and allow for accurate side-by-side product comparisons. As such, LCAs and EPDs are an excellent way to prevent ‘greenwashing’—defined by the Oxford English Dictionary as “disinformation disseminated by an organization so as to present an environmentally responsible public image.”
‘Product benchmarking’ is a baseline assessment of environmental impacts across all relevant categories—from extraction of the product’s raw materials to its end-of-life disposition. Benchmarking and quantification of environmental impacts are necessary elements of green building because they provide a better method of making apples-to-apples product comparisons. Accurate measurements of products’ environmental impacts enable reduction of the overall building’s environmental impact.
The three tools discussed in the following paragraphs—LCAs, PCRs, and EPDs—work together. Product category rules are first developed, a lifecycle assessment is performed according to the PCR, and an environmental product declaration publishes the results of the LCA.
A lifecycle assessment is an analysis of every component of a product’s manufacture and use. The lifecycle includes raw material extraction and transportation to manufacturing site (i.e. extraction phase), manufacturing, transportation to the jobsite and construction (i.e. construction phase), use, and end-of-life phase. (LCAs have some commonalities with lifecycle cost inventories [LCCIs]—used by individual companies for decades to evaluate their product supply chain for pinpointing inefficiencies and expense-cutting opportunities—but the two are not the same.)
An LCA that complies with International Organization for Standardization (ISO) 14040, Sustainability in Building Construction–Environmental Declaration of Building Products, is conducted by an independent third-party, ensuring unbiased results and confidence by end users.
This lifecycle phase include the impacts due to extracting raw materials and transporting them to the manufacturing site. For instance, products using aggregate as a raw material include the quarrying of the material and its transportation to the manufacturing site in their extraction phase. For short-haul distances, roundtrip transportation is considered because the truck that delivers the aggregate would directly return to the quarry for an additional load. (Where recycled materials are used, their impacts are allocated to their original product and to the new product according to a separate analysis outside the scope of this article.)
This phase includes all operational energy required to run the manufacturing plant, as well as all upstream energy to create the operational energy. (This is significant because for standard grid-delivered electricity, about two-thirds of the energy is lost during transmission. That is, for every 1 kWh of electricity used at the manufacturing site, about 3 kWh of electricity are made.) For product-specific LCAs and EPDs, this phase looks specifically at local energy grid sources.
This means identical plants manufacturing the same product can have different impacts in the manufacturing phase depending on where in the country they are located and what kind of fuel is used to generate electricity (e.g. manufacturing sites relying on coal combustion will have a higher carbon footprint than those relying on natural gas combustion, as the carbon emissions per unit of energy for coal are about twice as high as those for natural gas). Where manufacturers use renewable energy, such as locally mounted solar panels, there is a corresponding reduction in environmental impacts.
This phase includes transportation of finished products to the jobsite and accessory materials required for construction, as well as the construction itself. For example, the lifecycle of brick includes the use of mortar because a brick wall cannot generally be built or function without mortar. Depending on the distance the finished goods are transported, the LCA will consider one-way or two-way transportation. For example, brick and ingredients for mortar are generally moved on flatbed trucks on an as-needed basis by contract haulers. Consequently, one-way transportation is considered for this phase, as back-hauls on flatbed trucks are common and expected.