On January 1, California pulled a stack of mid-size commercial buildings under the same embodied-carbon rules that had applied to large commercial projects since mid-2024. CALGreen’s mandatory embodied-carbon threshold dropped from 100,000 square feet to 50,000. A cohort of buildings that had been exempt on December 31 was not exempt on January 2.

Six months in, the operational picture is clearer than the compliance overhead the industry was bracing for. The developers most exposed have been the ones who spent the second half of 2025 assuming a further delay would materialize. It didn’t, and it isn’t going to.

The visible headline in January was the CALGreen threshold itself. The more important story has been what has happened in the widening ring of cities that don’t get the same press coverage, and the compliance rhythm that mid-size builders are now settling into whether they were ready for it or not. The bigger story still to come is the August 10 disclosure deadline sitting three weeks out on operators’ calendars.

What actually changed at the 50,000-square-foot line

CALGreen’s mandatory measures give designers three compliance pathways: adaptive reuse of an existing structure, a whole-building life-cycle assessment demonstrating a percentage reduction against a baseline building, or a prescriptive route based on product-level global warming potential limits verified through Environmental Product Declarations. Each pathway carries real cost implications. Reuse is the cheapest carbon route but the most operationally complex. WBLCA requires competent consultants and material take-offs that many mid-size projects have never had to produce. The prescriptive route sounds simplest but effectively locks specifications early, which does not sit comfortably with how mid-size developers actually run design.

None of these mechanics were new in January. What was new was who had to run them. A 55,000-square-foot mixed-use building in a secondary California market moved inside the same regulatory perimeter as a Bay Area office tower, and the design team was usually smaller, the consultants less specialized, and the schedule less forgiving of the discovery work embodied-carbon reporting demands.

Six months in, three patterns are visible from the design-firm side of the industry. WBLCA has become the pathway most mid-size projects are defaulting to, because it accommodates late design changes better than the prescriptive route does. Prescriptive is showing up mostly on repeat-typology projects — hotels, self-storage, warehouses — where specifications are stable enough that early lock-in isn’t a schedule risk. Reuse, despite being the cheapest carbon route, remains rare in mid-size project pipelines because the acquisition and entitlement work is heavier than the compliance savings.

The pattern is bigger than California

The Carbon Leadership Forum has been tracking embodied-carbon requirements affecting private commercial and large multifamily construction across North America. The current list includes CALGreen, Berkeley’s Green Building Requirements sections 4.405.1 and 4.408.1, San Francisco’s Construction and Demolition Debris Recovery Law, Palo Alto Municipal Code Section 5.24, Marin County Code Section 19.07, Denver Building Code sections 901.3.2.1 and 901.3.2.2, New Jersey Senate Bill 3091, the Vancouver Building By-laws, and Toronto’s Green Building Requirements. That is eleven distinct regimes in North America alone, and the New Buildings Institute has published embodied-carbon code overlays for both the International Building Code and the International Residential Code that any jurisdiction can adopt substantially as-is.

Two rough typologies have emerged. Prescriptive rules set caps on specific high-carbon materials — concrete, steel, aluminum, insulation — and require verification through EPDs. Performance rules require a whole-building assessment demonstrating an improvement against a reference building. Most mature regimes now combine both, giving developers a menu but requiring documentation either way.

The August 10 layer

The disclosure rules are what a lot of operators are actually working on right now. California’s Climate Corporate Data Accountability Act, SB 253, has its first mandatory reporting deadline on August 10 — a little over three weeks from the publication of this brief. The California Air Resources Board finalized the implementing regulation at its February 26 board meeting, ending months of rulemaking uncertainty. Companies doing business in California with more than $1 billion in annual revenue must report Scope 1 and Scope 2 emissions from fiscal year 2025 data by that date, with Scope 3 including embodied carbon following in the 2027 cycle.

SB 261, the companion climate-related financial risk disclosure statute, is separately on hold. The Ninth Circuit issued a preliminary injunction that applies specifically to SB 261, and CARB’s December 2025 enforcement advisory confirmed no enforcement against the original January 1, 2026 deadline pending the appeal. SB 253 was not affected by the injunction and remains fully in force.

For any national developer, embodied carbon has moved from a design consideration to a financial-reporting one. Any operator running a 2026 pro forma without a Scope 3 accounting line for embodied carbon in projects breaking ground this year is running the wrong pro forma.

Why mid-size builders were the exposed cohort

Large developers had been running WBLCA on flagship projects for years before January. Their design teams included sustainability consultants, their contractors had relationships with EPD-equipped suppliers, and their in-house counsel had already priced the compliance overhead. They absorbed the January threshold drop the way they absorbed the last one: with irritation but without material disruption.

The exposed cohort has been the developer whose portfolio sits between 40,000 and 80,000 square feet — the class that lived comfortably above the residential threshold but below the commercial one until January. Municipal caps rarely arrive with generous transition windows. Denver’s requirements attach to permit applications after their effective date. CALGreen’s rule triggers on permit submission after the effective date, with no phase-in for individual projects. A permit application filed on December 30 escaped; the same application filed on January 2 didn’t.

The EPD supply-chain question, six months in

The quieter compliance question was always going to be upstream. Prescriptive rules require product-level EPDs to verify limits, and EPD coverage varies enormously by material category. Structural concrete has good EPD availability from major suppliers in most markets. Structural steel is well covered. Rebar is uneven. Insulation is patchy at the manufacturer level. Glazing systems are frequently reported at the component rather than assembly level, which complicates verification.

What has actually shown up in Q1 and Q2 is exactly what design firms warned about: mid-size developers discovering, three weeks before a permit deadline, that a substituted product cannot be verified against the prescriptive limit and that the alternate substitution changes project cost. That’s the practical form the compliance shock has taken. Not a legal problem, a procurement one.

What to do now

The developers handling this well are doing three things at once. They have run a shadow WBLCA on one recent project to establish an internal baseline and identify which product categories drive their embodied-carbon score. They have audited their preferred-supplier lists for EPD availability at the SKU level rather than the manufacturer level. And they have pushed their design teams to select structural systems earlier in the schedule, which is uncomfortable but necessary if the prescriptive route is going to be viable on a given project.

None of that requires new regulation to be worthwhile. The upstream disclosure rules alone create financial-reporting exposure for developers doing business with regulated buyers. Embodied carbon has quietly become part of the operating stack for any developer above roughly $500 million in annual revenue. Six months of CALGreen enforcement at the 50,000-square-foot line, and now an August 10 SB 253 deadline three weeks out, has made that fact undeniable for a group of builders who spent 2025 believing it was someone else’s problem.