Whole building life cycle assessment through LEED v4
As the architectural and construction industries increasingly emphasize sustainability, more comprehensive methods are being developed to evaluate and reduce environmental impacts by buildings. Over the years, holistic environmental assessment of buildings, building components and building materials from has gained significant importance.
LCA and LEED v4
LEED v4 Building Design and Construction (BD+C) includes a new credit, Building Life-cycle Impact Reduction. One of the options available for this credit is Option 4: Whole building life cycle assessment (LCA), worth three points, with a possible exemplary point. The new credit encourages projects to make early design decisions to reduce environmental impact. LCA is a tool that allows architects and other building professionals to understand the energy use and other environmental impacts associated with all life cycle phases of the building: raw material procurement, manufacturing, construction, operation and decommissioning.
LCA is the cradle-to-grave quantification of potential environmental impacts of products or services. It considers the entire value chain using the ISO 14040/44 standard. LCA removes the guesswork; one can assess buildings to understand their environmental “hot spots” and identify greener alternatives. Commonly reported impact metrics include global warming (“carbon footprint”), acidification (“acid rain”), eutrophication (“algal bloom”), photochemical oxidant creation (“summer smog”) and ozone depletion (“the ozone hole”).
The details on requirements
The LEED v4 Building Life-cycle Impact Reduction credit requires improving building life cycle impacts by 10 percent compared to a baseline building (the performance requirements are found in ASHRAE 90.1-2010), using a life cycle assessment software. Other requirements include:
- The baseline and proposed buildings must be of comparable size, function, orientation and location.
- The energy performance for the proposed building has to demonstrate a minimum energy improvement of 5 percent (BD+C: New Construction), when compared with the baseline building.
- The service life of the baseline and proposed buildings must be the same, and at least 60 years, to fully account for maintenance and replacement.
- The LCA must be calculated for six listed environmental impact categories (global warming potential (greenhouse gases), in kg CO2e; depletion of the stratospheric ozone layer, in kg CFC-11; acidification of land and water sources, in moles H+ or kg SO2; eutrophication, in kg nitrogen or kg phosphate; formation of tropospheric ozone, in kg NOx, kg O3 eq, or kg ethene; and depletion of nonrenewable energy resources, in MJ) with three of them, including global warming potential, demonstrating at minimum a 10 percent reduction.
- No category of impacts may increase by more than 5 percent, compared to the baseline design. The scope of the LCA should be a cradle-to-grave assessment, from design to demolition. The LCA should follow the system boundaries A1–A4, B1–B7 and C1–C4 according to ISO 21930 for the building structure and enclosure. This includes the product stage, construction process, use stage and end-of-life stage.
- In addition to the three points, an extra point is awarded through the Innovation credit by displaying reduction in all six impact categories by 10 percent, instead of only three, as LEED v4 requires.
LCA is a long‐established, credible, multi‐criteria method for the transparent evaluation of a wide range of goods and services. The comparison of whole building LCA results and of individual impact parameters, for each design alternative between baseline and proposed building design, can guide teams in achieving the goal of sustainable design.