by Lauren Richardson
Sustainability Manager at Green Badger
For a long time, embodied carbon was something everyone agreed was important, but almost nobody had to deal with it. It lived in conference keynotes and pilot credits.
That’s over. Embodied carbon is now a prerequisite in LEED v5 and a mandatory requirement in California’s building code. More states are following suit. If you’re a GC or sustainability manager, this is a line item on your projects today. Not someday. Today.
In our last post, Embodied Carbon on Real Projects: What Teams Are Actually Tracking, we covered what field teams track day to day. This one goes deeper: what the rules require, where LEED v5, CALGreen, and state Buy Clean requirements align, and how to build one process that checks all boxes.
Why Timing Matters for Embodied Carbon
Embodied carbon is the carbon from making, moving, and installing your building materials. It’s the footprint of your concrete, steel, glass, and insulation before the building ever turns the lights on.
Operational carbon can be tuned over decades with better controls, retrofits, or a cleaner grid. Embodied carbon gives you one shot: procurement. Once the concrete is poured, the carbon is locked in.
That’s why the rules focus on the buy. That’s why contractors are at the center of it.
LEED v5: From “Nice to Have Points” to “No Certification Without It”
Under LEED v4 and v4.1, embodied carbon was optional. You could chase a WBLCA credit, collect EPDs for points, or skip it all and still get certified.
LEED v5 closes that door. Embodied carbon now shows up in two places.
The Prerequisite: Quantify and Assess Embodied Carbon (MRp2)
This is the big one. MRp2 is mandatory. Every LEED v5 project has to measure its embodied carbon.
The prerequisite doesn’t require a reduction target. It asks you to know your number. In practice, that means:
- Calculating the embodied carbon of your major building elements — structure, enclosure, and hardscape
- Using actual material quantities and real product carbon data
- Identifying the biggest carbon drivers on the project
For contractors, someone must collect installed quantities by material and manufacturer and pull the corresponding EPDs.
The Credit: Reduce Embodied Carbon (MRc2)
Once you’ve measured, LEED v5 rewards you for doing better. MRc2 awards points for coming in below a baseline, and there are two main ways to get there.
Path 1: Whole-building LCA. The design team models the building and compares it to a baseline.
Path 2: Product-based comparison. The team compares the GWP of selected products (from their EPDs) against industry baselines like the Carbon Leadership Forum (CLF) material baselines. This path is in procurement and submittals, where the GC has the most control.
Either way, the credit is based on the actual products you buy and not the design-stage estimate. Early numbers are fine for setting a baseline, but the procurement-stage actual is the number that counts.
A quick note on baselines: A baseline is the industry average for a material — the number you’re trying to beat. Think of it like a fuel economy sticker. Before you know if a car is efficient, you need to know what’s normal for that class. The CLF does the same for building materials. They analyze EPD data from thousands of products and publish an average GWP by material category. MRc2 isn’t asking “is your carbon number low in absolute terms?” It’s asking “is your product better than typical?” The CLF baseline is that yardstick.
CALGreen: Embodied Carbon Is Now Code
If LEED v5 is the carrot, CALGreen is the rulebook.
California was the first state to mandate embodied carbon reduction in its building code. LEED is voluntary. The building code is not. Any nonresidential new construction over 50,000 square feet must comply.
Here are the sections that relate to embodied carbon:
Building reuse (Section 5.105.2). Maintain at a minimum 45% combined of the existing building’s primary structural elements and building enclosure. The lowest-carbon building is often the one that’s already built.
Whole-building LCA (Section 5.409.2). Show at least a 10% GWP reduction compared to a reference baseline building of similar size, function, complexity, type of construction, material specification, and location using a cradle-to-grave WBLCA.
Product GWP limits, Prescriptive Path (Section 5.409.3). Show that key materials come in under maximum GWP values established in Table 5.409.3. Each product must have a Type III EPD (product-specific or factory-specific). The covered materials are:
- Structural steel
- Concrete reinforcing steel
- Flat glass
- Mineral wool board insulation
- Ready-mixed concrete
For concrete, a weighted average across all mixes installed on the project is allowed. Industry-wide EPDs are acceptable for concrete only.
For most GCs, the prescriptive path is the most familiar. It’s a submittal review with one more number to check. The catch is the number must be known before you buy, so the EPD has to be in hand before the mix gets approved.
Where LEED v5 and CALGreen Overlap
If you’re building a LEED v5 project in California, you’re dealing with both. Here’s the good news: the data is almost the same.
- Installed material quantities by product and manufacturer
- Product-specific Type III EPDs
- GWP values in consistent, comparable units
- A clear baseline to compare against
The difference is what each does with the data. CALGreen asks, “Did you pass?” LEED v5 asks, “How did you do and can you do better?”
The smartest move is to build one data set that serves both. Collect it once, organize it by structure, enclosure, and hardscape, and use it for code compliance and LEED documentation.
CALGreen vs. Buy Clean California — What’s the Difference?
Buy Clean California is about public money. If the state is paying for a highway, a bridge, or a public building, the steel, concrete, and glass that goes into it has to meet carbon limits. The government isn’t going to spend taxpayer dollars on high-carbon materials anymore.
CALGreen is about building permits. If you’re building anything nonresidential over 50,000 square feet in California (with anyone’s money), you have to meet carbon limits to get your permit.
Buy Clean says, “You want state money? Follow the rules.”
CALGreen says, “You want to build in California? Follow the rules.”
CALGreen borrowed its carbon limits directly from Buy Clean and made them slightly less stringent. If you’re already tracking EPDs for one, you’re most of the way there for the other.
States, Cities, and the Federal Government Are All Moving in the Same Direction
It’s not just California. States across the country are starting to require embodied carbon accountability through Buy Clean legislation. California led with the Buy Clean California Act, setting hard GWP limits on structural steel, rebar, flat glass, and mineral wool insulation for public projects. Colorado, Maryland, Michigan, Oregon, and others have followed with their own versions, targeting the same core materials and requiring EPDs to prove compliance. Cities like Boston are joining too. At the federal level, GSA and DOT have moved to embed Buy Clean requirements into public procurement. The direction is clear and not reversing.
What This Means in Practice
If you’re working in LEED v5, here’s the good news: the EPDs, CLF baselines, and material categories are all the same infrastructure. A solid MRc2 workflow and Buy Clean compliance run on the same data. You’re not building two systems but one that works for both. This isn’t just about chasing a plaque. It’s about being ready for where the industry is heading.
Confirm requirements at kickoff. Is this a LEED v5 project? Is it over the CALGreen threshold? Which compliance path is the design team using?
Write it into the contract. Include EPD and quantity requirements in bid packages and subcontracts. If it’s not in the scope, it won’t show up in the submittal.
Use a takeoff sheet from day one. Green Badger’s Material Takeoff Sheet and instructions give trades one format for material, manufacturer, quantity, units, and location.
Check the data, not just the paperwork. Before filing an EPD, confirm it’s a Type III EPD, current, matches the installed product, and its declared unit aligns with the baseline. An EPD in cubic feet won’t match a baseline in metric tons without a density conversion.
Track during construction, not at closeout. Finding out a concrete mix exceeds the CALGreen limit after it’s poured is a problem you can’t fix. Flag it at submittal while there’s still time to change the mix.
The Bottom Line
Embodied carbon is required now. LEED v5 makes measuring it a condition of certification. CALGreen makes reducing it a condition of the building permit for a growing number of California projects. Buy Clean policies are pushing in the same direction.
The teams that do well here aren’t the ones with the most sustainability experts. They’re the ones that build embodied carbon into the processes they already run: bid packages, submittals, and procurement.
Green Badger’s EC3 integration brings verified data from more than 100,000 products straight into your project — so you can track GWP, compare alternatives, and document compliance without a spreadsheet maze. Book a demo to see how it works.
