LCA for buildings
Life cycle assessment (LCA) is the latest addition to the sustainability toolbox for buildings. LCA looks at the upstream and downstream burdens throughout the entire building life cycle, with a focus on embodied environmental impacts. Embodied impacts become more critical as operating consumption, such as energy and water, is reduced through optimization of design and building management.
LCA provides a quantitative basis for environmentally improved designs, removing the guesswork, unintentional greenwashing and burden shifting (when improvement in one life phase merely creates more burden in another phase).
The Athena Sustainable Materials Institute is the first North American organization dedicated to the use of LCA in construction. The Athena Institute is well-known for its common-good mandate to develop LCA data on construction materials and systems and to make these data accessible to building designers through user-friendly tools such as our Impact Estimator for Buildings.
Whole-building LCA and embodied carbon are part of some green building codes, standards and rating programs. See our page on LCA credits to learn more.
Whole-building LCA explained
As with any cradle-to-grave LCA study, LCA for a building measures all of the flows between a building and nature over its lifetime and then estimates the resulting impacts on air, land and water.
The cradle-to-grave lifetime of a building includes manufacturing and transporting of construction materials, the process of construction, a long phase of building occupancy and maintenance, demolition, and removal of waste materials. Resources are consumed and emissions created during every life phase.
At the core of a whole-building LCA study is a bill of materials. This includes types and quantities of the major materials that comprise the building, any material waste during product manufacturing and construction, and material replacements over the life of the building. Cradle-to-grave consumption of energy and water resources are also included: for example, product transportation to site, the operation of construction equipment, and, optionally, building operation.
This material and resource consumption data is translated into a life cycle inventory (an accounting of all the flows to and from nature), which is then run through a life cycle impact assessment model for LCA results: the impact of the building on global warming, acidification, smog and so forth.
Next step is to review the results. Do they make sense, where are the hot spots, and what’s next: maybe some what-if experiments, refining the design, re-running the model, and documenting the final results.
In all applications, LCA is used as an estimating science, not an exact one. This is particularly true when applying LCA to buildings, given the uncertainty in results due to data gaps, methodology variations, and the difficulty in predicting the future for a long-lived product like a building.
The Athena Impact Estimator for Buildings, our simplified LCA software tool, is provided for free to the sustainable design community in order to make whole-building LCA feasible in everyday practice. Want help learning the tool, or want to engage us to do a whole-building LCA study? Send us an email.
Embodied carbon explained
“Embodied carbon” is a shorthand way to refer to all the lifetime greenhouse gas (GHG) emissions due to a building other than for building operation. Most embodied emissions are upstream of building occupancy – they are primarily related to the manufacturing of materials.
Embodied carbon is simply the global warming potential (GWP) result from a whole-building LCA study. The Athena Impact Estimator for Buildings is ideal for calculating embodied carbon.
GHG emissions due to material manufacturing, use and disposal are more significant than many people realize. First, these emissions are a big upfront GHG pulse (versus the slow accumulation of GHG savings over time from low-carbon building operation), which makes them a good near-term target for climate change mitigation. Second, as buildings approach net-zero operation, embodied impacts will make up most of the carbon footprint in the built environment.
Embodied carbon has long been overlooked in sustainability strategy. This is starting to change. Some green building programs and policy are recognizing the importance of reducing embodied carbon through design decisions.
The Athena Impact Estimator for Buildings is ideal for calculating embodied carbon and exploring tactics for reducing it.
Want help complying with embodied carbon reporting requirements? We can do it for you, or coach you through it, on an hourly-fee basis. Contact us for more information.
See our briefing note on whole-building LCA and embodied carbon.