Life cycle assessment and buildings

As building teams attempt to assess the sustainable attributes of building products and systems, Life Cycle Assessments, or LCAs, and Environmental Product Declarations, or EPDs, are gaining attention. In 2010, the American Institute of Architects published the AIA guide to building life cycle assessment in practice [PDF]. More recently, the Carbon Leadership Forum published Life cycle assessment of buildings: A practice guide, in 2019. These are both good resources for life cycle assessment and buildings.

Whole building LCA is similar to a product LCA, but the product is the building. A complete whole building LCA includes all materials in the building but, for simplification, the LCA is often limited to only the materials found in the largest quantities or with the most impact. For a whole building LCA, the functional unit might be “the entire building from design to demolition for a 50-year service life,” or it might be computed on a per-square-foot basis and limited to one life cycle stage (e.g., construction).

Whole building LCA principles can also be used for a variety of purposes, such as:

To provide insights into building materials choices (including new products) and design options.
To show benefits of refurbishment vs. demolition plus reconstruction
To compare structural systems and finish choices for reduced environmental impact
To achieve an LCA-based certification, or to make environmental claims about buildings
To provide decision support for policy design, including the introduction of new building technologies
To provide guidance on product and process development, marketing, and selection of suppliers or subcontractors

The whole building LCA process is informed by ISO 21931, which sets standard references and modeling assumptions. ASTM standard E2921 further describes how to compare whole buildings LCAs in codes, standards, and rating systems. European standard EN 15978:2011 also codifies LCA for buildings and defines the following life cycle stages:

Life cycle stages

Product	A1	Extraction, production
	A2	Transport
	A3	Manufacturing
Construction	A4	Transport
Construction	A5	Construction, installation
Use	B1	Use
	B2	Maintenance
	B3	Repair
	B4	Replacement
	B5	Refurbishment
	B6	Energy Use
	B7	Water Use
End of life	C1	Demolition
	C2	Transport
	C3	Processing
	C4	Disposal
Beyond	D	Reuse, recycling, recovery

Building life cycle stages (adapted from ISO 21931 [13] and EN 15978 [12]).

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LCA tools for buildings

Athena Impact Estimator

The Athena Impact Estimator assists design teams in exploring the environmental footprint of different material choices and core-and-shell system options. It is a stand-alone program that allows users to model custom assemblies and envelope configurations, and provides flexibility for proposed designs and existing buildings. Technical knowledge of the building construction is required for data input. The Impact Estimator allows users to include energy simulation results to calculate operating energy effects alongside the effects of embodied energy.

BEES online

The Building for Environmental and Economic Sustainability, or BEES tool, helps design teams select cost-effective, environmentally-preferable building products. Environmental performance is determined using the ISO 14040 life cycle assessment approach. Results include life-cycle impact assessment results developed based on current Product Category Rules. Economic performance is measured using the ASTM standard life cycle cost method.

BIRDS

The Building Industry Reporting and Design for Sustainability tool, also called BIRDS tool, uses LCA and life cycle costing, or LCC, together to evaluate the sustainability of the materials and energy used in a building over its lifetime. It assesses 12 environmental impacts alongside economic performance to yield an assessment of the business case for design alternatives in buildings.

The BIRDS database includes energy, environmental, and cost measurements for over 12,000 new commercial and non low-rise residential buildings, covering 11 building prototypes in 228 cities across all U.S. states for 9 study period lengths.

One Click LCA

One Click LCA is a construction sector LCA software that allows users to calculate and reduce the environmental impact of building and infrastructure projects, products, and portfolios. The tool has a materials database and integrates with a variety of CAD/BIM and energy software tools. It also has a separate EPD generator tool. The software is not free, but a free embodied carbon version is available called One Click LCA Planetary.

Tally

The Tally application allows architects and engineers to quantify the environmental impact of building materials for whole building analysis as well as comparative analyses of design options. The user can define relationships between BIM elements and construction materials from the Tally database. The result is LCA on demand, and a layer of decision-making information that allows designers to evaluate various design options in real time. Tally is easy to use and requires no special modeling expertise, but it is not a free tool. The Tally methodology is consistent with LCA standards.

Embodied carbon

The current focus on carbon emissions has brought to light the importance of embodied carbon in materials. As buildings become more energy efficient, the global warming potential (GWP) of embodied carbon in building materials has a greater life cycle impact than carbon from operating energy.

EC3

The Embodied Carbon in Construction Calculator, or EC3 tool, is an open-access tool that allows benchmarking, assessment, and reductions in embodied carbon, focused on the upfront (Stage A1-A3) supply chain emissions of construction materials. The EC3 tool uses third-party verified EPDs.