Unlike many of the other Materials & Resources credits, this credit is about overall design and construction choices rather than using specific products.
This credit is applicable to any construction type, but the ways in which you can assess and document life-cycle impact reductions depends on where you’re starting.
Start by reviewing the four credit options to see which best applies to your project. The first three options all deal with building reuse, while the fourth option is broader.
Option 1. Historic buildings
Historic buildings have obvious cultural value, but preservation of any existing structure also provides environmental value by reducing the need to extract, manufacture, and transport new construction materials. This in turn lowers the life-cycle environmental impacts of a building—and can lower the cost as well.
Is this option for me?
If your building is on a historic registry, you’ve practically achieved this credit already. If not, you’ll need to show that it’s eligible for such a designation through alignment with existing local or national criteria for historic buildings. Check with your local planning board, or a government register of historic places, to determine if your building might be considered to have historic value.
Look out for paperwork.
If you’re attempting this path, you must show formal approval for design changes from a historic authority, planning committee, or historic buildings professional, even if your building is not officially on a historic registry.
What’s new in LEED v4.1
Should I upgrade?
Since this option hasn’t changed, there’s no need to do a one-off substitution.
Options 2 and 3: Existing and abandoned buildings
Is this option for me?
Options 2 and 3 are available for any existing building but may not be right for every existing building. Because compliance is based on the total amount of conserved materials, these options are best suited for projects where material preservation is a major project goal.
If there is substantial demolition or renovation work planned, Option 4 (see below) may be a safer bet. To guarantee success, develop a preservation plan and perform credit calculations as early as possible in the design process.
Note that for both Option 2 and Option 3, you can’t double count your preserved materials under Building Product Disclosure and Optimization–Sourcing of Raw Materials.
SITES-LEED equivalency is not offered for this credit. The related SITES credit cannot be used to automatically earn this LEED v4.1 credit.
What’s new in LEED v4.1
- Option 2 hasn’t changed.
- Option 3 has been split up and now has multiple paths, having restored the guidance from LEED 2009 about maintaining 1) a combination of structural and nonstructural elements, 2a) existing walls, floor, and roof, and 2b) interior nonstructural elements. You can’t combine paths 1 and 2.
- SITES equivalency has been removed.
Should I upgrade?
There’s no reason to do a one-off substitution for Option 2, since it hasn’t changed. Under the newly split up Option 3, you may find it easier to achieve at least some of the available points since you don’t have to preserve all of the building elements as required under v4.
Notes on Options 1, 2, and 3: What’s in and what’s out
For these options, compliance is based on the percentage of surface area that’s being reused or preserved. Both exterior and permanently installed interior elements should be included in these calculations, including the surface area of up to three separate layers in each assembly.
For example, if you keep a brick wall but replace the drywall on the inside face, you’ll still get partial credit for preserving the assembly. One layer must be structural, and the other two layers must be interior and exterior finishes.
For buildings officially considered blighted or abandoned by a local authority, up to 25% of the surface area can be excluded from the calculations if it’s deteriorated or damaged. Hazardous materials can also be excluded from both options. If you remove a layer of an assembly and don’t replace it, you can exclude that layer from the calculations since you haven’t created a demand for new materials. Lastly, window assemblies are excluded from credit calculations, so you won’t be penalized for upgrading to more-energy-efficient frames.
Look out for salvaged materials.
Salvaged materials from both on and off the project site can contribute to reuse calculations. This provides a path to claim the environmental benefits of the reused materials if it’s too difficult to estimate replacement costs for MRc3: Sourcing of Raw Materials. However, salvaged materials are only significant in the calculations if they replace an existing material—in which case the salvaged layer gets counted as reused. If it’s a newly added layer, then it has a neutral impact in the calculations, so it’s not possible to achieve this credit through adding salvaged materials alone.
Option 4: Life-cycle Assessment
Life-cycle assessment (LCA), as it applies to buildings pursuing LEED, involves creating an inventory of the environmental impacts associated with building materials’ manufacture, transportation, use, and disposal. Think of it as a life-cycle cost estimate, only in this case the “costs” are metrics in key environmental impact areas (called “indicators” in LCA terminology). Commonly used LCA indicators represent atmospheric impacts, fossil-fuel resource depletion, and some ecological effects.
LCA is intended to be an iterative modeling tool that informs decisions during the design process, much like an energy model. It can be a time-intensive process, but if it’s set up to support broader project goals and not just the LEED credit, LCA can be a rewarding way to validate sustainability strategies that are otherwise hard to assess.
How you use the LCA will likely depend on when the process begins relative to design decisions, the context of your project, owner commitment, and the time and resources available to updating the model. Committing to using LCA as a tool throughout the design process will reduce the risk of missing targets and can help you get the most value from the process.
First, define your goals
To achieve Path 1, all you need to do is conduct an LCA. It’s a way to get your feet wet without having to show specific levels of impact reductions. You can get a point for this approach.
Path 2 offers two points, with a lower threshold than previously required in LEED v4. You must demonstrate a 5% reduction in three of the six impact categories (the six are ozone depletion potential, acidification, eutrophication, tropospheric ozone formation, and non-renewable energy resource depletion), one of which must be global warming potential, or GWP—commonly referred to as embodied carbon.
To achieve Path 3, your project must demonstrate at least a 10% reduction in global warming potential and at least two of the five other basic indicators. Since many choices may have tradeoffs in environmental impacts, decide early in the process which indicators you want to prioritize.
Think carefully about which elements have the most influence over your project’s life-cycle impacts, and which areas you have the most control over. This credit specifically excludes all MEP equipment and operating energy, so it’s all down to design optimization and material selection.
For a newly constructed building, there might be a few specific materials that provide opportunities: maybe all the glass on the market turns out to be essentially the same in terms of environmental impacts, but you have control over selecting a locally made concrete with high fly ash content.
Items such as interior finishes and furniture are optional, but don’t plan to spend too much time over details in your LCA that have small effects on life-cycle impact reductions. These items should really only be included when other opportunities are limited, or if the LCA is going to help inform selection of a particular type of product, such as drywall with a reduced carbon footprint.
Select an LCA tool
There are many different databases and public LCA tools out there. Some are free, some aren’t, some are easy, some are complex, and some may even integrate with existing design software. It’s important to find a tool that aligns with your experience level and will provide the right information to document this credit. Start by asking the following questions:
- Is the tool recommended specifically for evaluating buildings?
- Does it follow standard methodologies? Look for ISO 14044 and ISO 21930 or EN-15804.
- Does it measure the six basic indicators required for LEED compliance (global warming potential, ozone depletion potential, acidification, eutrophication, tropospheric ozone formation, and non-renewable energy resource depletion), and any others that are important to my goals?
- Does the tool’s database cover my project’s region?
- Does it allow for custom inputs if I want to include a specific product?
- Will the inputs be easy for me to calculate and update as I go?
Define your baseline
Just like with an energy model, the results of an LCA only make sense as a comparison against a baseline. However, unlike with an energy model, there are no hard-and-fast requirements for what should be included in that baseline.
The LEED Reference Guide provides some specific requirements for the baseline that are designed to create one that is “functionally equivalent” to the proposed case. In other words, the baseline should meet the project brief and any regulatory requirements, and have the same gross floor area, program, and location as the proposed building. It should also use assemblies that can meet the insulation requirements of EAp2: Minimum Energy Performance (don’t forget, in this case the minimum energy performance required by LEED certification is another functional requirement!). Lastly, the source, quality, and precision of the data should be the same in each case to create a valid comparison.
Outside of that guidance, the requirements are vague because what defines an appropriate baseline really depends on the project’s context and goals. It is critical to begin the LCA with a clear understanding of what you’re comparing your project against and how that comparison will drive design decisions, as well as what design variables will be in play.
Refine and assess until goals are met
Use the LCA as a tool to evaluate potential major decisions, and weigh the change to each of the six indicators against other considerations (such as energy consumption, cost, or availability).
Start with an early conceptual model and include major structural and envelope components, even if generic. The results of this early model may not match your final design, but it’ll provide the relative contributions of each material to the building’s overall impacts and tell you where the best opportunities are for further reduction—and where not to spend too much effort on alternatives. For example, window assemblies might have high embodied energy, but if your building’s window-to-wall ratio will only be 15%, then it will make more sense to focus on the wall assemblies instead.
Updating the LCA model as you go
As the design progresses and becomes more detailed, the LCA should get more detailed as well.
Continue to update the model and track how the impacts change relative to the original results until the project’s goals are met.
- Example. A new building is built in a confined urban lot with strict zoning requirements that determine the massing. The team decides that the biggest impact is in their material selection. They look at other new buildings in the area to come up with a baseline material palette. After creating a baseline that’s the same shape as the proposed building, they compare the life-cycle impacts of façade options and select the one with the greatest reduction in global warming potential.
What’s New in LEED v4.1
- “Path 2” reintroduces the LEED 2009 language about reusing existing building structure and skin (Path 2a), and existing interior elements (Path 2b). While the calculation methods are familiar from the old LEED, the thresholds in 4.1 are lower, making these points easier to achieve than they used to be.
- Option 4: Whole-Building LCA now has several additional paths. Two of these new paths are stepping stones, creating an easier entry point for those encountering whole-building LCA for the first time. There is also a new Path 4 that assigns the most points (four) to a solution that offers the most significant reduction in embodied carbon.
Should I upgrade?
Version 4.1 opens up several new choices that could put this credit in reach for a lot more projects. Path 1 is especially helpful as it provides an entryway into LCA for first timers. And who knows? If you define a baseline building, you could even achieve one of the other options.