Changes in LEED v4.1 make life cycle assessment and embodied carbon management more flexible

Changes in LEED v4.1 make life cycle assessment and embodied carbon management more flexible 600 392 Mantle

You’ve probably heard of a “LEED Building”; you may even live or work in one. LEED (Leadership in Energy and Environmental Design) is the most popular green building rating system in the world. Its voluntary best-practices have played a major role in the greening of the construction industry. Canada has over 3,800 LEED buildings. Over a quarter of all new institutional and commercial buildings in Canada target LEED.

The newest version of the building design and construction (BD+C) standard – v4.1 – was released in December 2018. Although billed as an incremental update, v4.1 does include some significant improvements and, among other things, provides more options to teams wanting to address embodied carbon (expressed in LEED as ‘global warming potential’).

The system is updated every few years to reflect ever-evolving best practice in construction. The previous update – LEED v4, launched in late 2013 – added a new strategy not seen in previous versions: whole-building life cycle assessment (LCA). This credit awards project teams that reduce embodied carbon by selecting construction materials from lower carbon sources. This could include strategies such as using concrete with a higher percentage of recycled materials, specifying 100% recycled steel, or prioritizing carbon-storing mass-timber harvested from responsibly-managed forests in your structure. A number of our previous blogs provide an overview and roundup on other meaningful approaches to reducing embodied carbon. LCA is the methodology used to measure embodied carbon and several other types of pollution that result in environmental damage like toxicity, acid rain, aquatic degradation, ozone depletion and smog formation.

The inclusion of LCA in v4 was a major step in bringing the concept of embodied carbon and LCA out of academic discussions and into the mainstream construction design community. Its importance was recognized by assigning three LEED points to the LCA credit, whereas most LEED credits carry a single point. Additionally, an exemplary performance option could award a fourth point, and in some cases a regional priority credit another still – for up to five points being available. The credit was achieved if the LEED building was able to demonstrate at least a 10% reduction against a reference building in at least three environmental damage categories (LEED’s LCA credit includes six categories). One of the three must be embodied carbon. Additionally, none of the categories can be 5% worse in the LEED building vs the reference.

This approach was a good first start. It recognized the importance of climate change (global warming) by prioritizing embodied carbon as the only category that was required to be reduced. Any other two categories could be used to round out the three-category 10% reduction requirement. The approach also addressed the trade-offs inherent in design decisions by requiring that no category can be 5% worse in the LEED building vs the reference. This means that project teams can’t get the three LCA points if their solution saves one element of the environment by sacrificing another. For example, the production of certain types of building insulation could result in toxic emissions or smog; we don’t want to have a zero-carbon building at the expense of clean air.

Although this credit shifted the market and brought discussions of LCA and embodied carbon to project teams, its uptake was slow. Firstly, most project team members had little to no experience with LCA. They didn’t know where to start and were nervous to begin what they perceived to be a steep learning curve without having any sense of the results. “How much will this cost? Will we have to specify different materials? Are you sure we’ll get the three points?” These were questions that most project teams couldn’t answer. Although some teams were likely attracted to this credit for the high value associated with it (three to five points), just as many if not more project teams were likely scared away from the ‘all-or-nothing’ structure of the three base points since no option existed to achieve one or two points. They didn’t have the LCA experience to know what it would take to achieve those three points and couldn’t guarantee them to the client. Losing three points towards the end of your certification process could make or break your target threshold (Silver vs Gold vs Platinum). This made the LCA credit high-reward, but also quite high-risk for those not familiar with this type of analysis.

The updates in v4.1 address this by restructuring the points to a sliding scale. The better your building performs, the more points available. Project teams can now achieve points according to the following:

  • First point: awarded for conducting the LCA in accordance with the methodology and data requirements.
  • Second point: awarded if the LCA demonstrates a 5% reduction in the LEED building vs a reference building in at least three of the six categories, one of which must be embodied carbon (global warming potential).
  • Third point: as above with at least 10% reduction.
  • Fourth point: awarded if the LCA demonstrates a 20% reduction in embodied carbon and 10% reduction in any two other categories. Incorporate building reuse and/or salvage materials into the project.

Points two through four require that no category can increase by more than 5% in LEED building vs reference building.

This revised approach awards project teams no mater how good or bad the building’s LCA-based environmental impacts are calculated to be. It allows project teams to ‘guarantee’ at least one point just by performing the LCA and introducing the design and construction team to the process. This is a very different opportunity/risk balance than the previous approach and allows the LEED consultant to approach the client, saying: “Let’s perform an LCA. We’ll get at least one point and won’t have to change the materials we end up selecting; this is just an information gathering exercise to help us better understand our impacts. We might also identify some opportunities for minor changes that could result in an additional one to three points”. This proposition carries much less risk and allows an easier and less daunting introduction to LCA.

Projects already registered under LEED v4 have the opportunity to ‘substitute’ v4.1 rules on a credit-by-credit basis. The v4.1 rules are currently in beta, however teams who ‘opt-in’ to using them for a given credit are able to lock-in the currently posted version. This means that even if the v4.1 rules are revised in the future, locking in the substitution now will preserve the current version for your project. ‘Locking-in’ the substitution to v4.1 rules for this credit is strongly encouraged as they carry significant benefit and no apparent downside.

Contact Mantle for more information on performing a LEED-compliant life cycle assessment (LCA) to understand and reduce your project’s embodied carbon and get up to five LEED points!