California Air Resources Board

I appreciate CARB’s charge to reduce the embodied carbon of building materials in California and the opportunity to share comments. I share CARB's goal and have spent the past 25 years of my professional career in pursuit of green building as a licensed architect, a LEED AP and, for the past 18 years, as a sustainability and green building consultant. I served for 10 years as the public member of the San Francisco Municipal Green Building Task Force and have consulted for public agencies and private clients in California on projects ranging from single family homes to libraries, office buildings, and airport terminals. I am an Associate Principal at the sustainability-focused engineering, design and consulting firm Arup, but these comments are my own (though I hope widely shared among my professional colleagues).

I understand that CARB has been charged with first developing a reporting system to gather data on embodied carbon in building materials, which it will presumably also use to track progress towards the 40% reduction goal. However, I believe strongly that the reporting system will both influence the direction of future reduction strategies and that it could quite likely be burdensome to industry. In addition, CARB’s excellent economic work to date (and widespread industry knowledge) has already established the primary materials where reductions would need to occur. Accordingly, my comments here outline reduction strategies in order to provide recommendations on how reporting can be designed to be most rational, efficient, and ultimately successfully within the building industry.

Because there are very significant differences among construction materials in how they are produced, handled, and installed, a one-size fits all approach to reporting on materials and projects both fails to advance the most impactful strategies and is not cost-effective. CARB’s current proposal for material and building reporting could be greatly strengthened by being aimed at specific sectors, while also reducing unnecessary impacts on the industry. I am concerned that, from an “Abundance” framework, CARB’s current plans to require reporting on all material manufacturing and importing and all projects (above cutoff thresholds) would place a large burden on the construction industry, driving up the cost of construction, with very little impact in GWP reduction in many cases.

These comments address concrete (including cement) and asphalt, steel, and wood as these are where I have the greatest experience with pursuing GWP reductions. I believe that a similar approach based on understanding the patterns of utilization and existing opportunities for GWP minimization within the other major material sectors (glass, insulation, etc.) could lead to the most effective and cost-effective reporting program and, ultimately, impact.

1. Cement, Concrete, and Asphalt
a. Because more than half of these materials are purchased by public sector agencies (US DOE: Pathways to Commercial Liftoff: Low-Carbon Cement), CARB should work with state (e.g. CalTrans, High-Speed Rail, Department of Water Resources) and local (Public Works) agencies that purchase concrete and asphalt to set GWP requirements on public projects. Having low-carbon mixes for different typical applications of concrete widely available in public sector us will make it much easier for the private sector to get compliant mixes. (e.g. for private civil projects using concrete, my experience is that every local supplier just wants to sell you a Caltrans mix). Public-sector purchasing leadership should be the primary focus on regulation of these materials, which will make it practical to extend the GWP limits in CALGreen 5.409.3 downwards over time and to include asphalt used in private projects.
b. Reporting should be focused on the limited number of concrete suppliers (batch plants, ready-mix companies, and precasting companies) in the state, rather than the very large number of projects using concrete, both to minimize cost burden on the industry and to improve accuracy. Project-level reporting has a very large room for error given the many details of concrete mix design, placement, and procurement; whereas concrete supplier reporting can give a very accurate picture of progress towards the GWP reduction target. Concrete suppliers are already aware of and able to report on the inputs and outputs of their businesses that are related to GWP in detail. In contrast, regular reporting of concrete GWP and volume at the project level comes with a substantial cost and at present is restricted to leadership projects within the building industry: at a guess, 5% of projects.
c. Supplier-level reporting will also provide a more effective focus for regulatory intervention, because the concrete supplier plays a key role in the ultimate selection of a concrete mix due to regional variations in climate, soil chemistry, and available materials, as well as day-of conditions like temperature, or truck-access distance to a pouring site. Projects that fail to meet low-GWP targets will likely be concentrated with a set of low-performing concrete suppliers; educating (or penalizing) those suppliers will improve the performance of many projects most cost-effectively, where local and regional factors can be addressed. While owners, contractors, and engineers will also need education to play their roles in achieving a project with low-carbon concrete, they often have less responsibility for the ultimate concrete mix selection than their suppliers.

2. Steel
a. There are limited options for reducing GWP of steel in construction:
i. Substituting wood for steel is typically effective at the project level, but is likely not practical or desirable at the statewide scale due to the limit of wood supply and the unwanted impacts of vastly increasing wood supply (e.g. deforestation and the increases in climate change, loss of biodiversity, etc. that come with it), unless a program of sustainable forest management both within and outside California can be part of the embodied carbon program.
ii. Design optimization of steel structures (using less material to accomplish the same goal) is a desirable outcome, but exceedingly hard to establish an appropriate baseline for, making it impractical to administer. Except in specific standard elements (e.g. floor slabs) and formulaic buildings, there are so many structural options and factors (bay spacing, deck span, importance factor, transfer loads, wind loads) and potential varieties of use that defining what a standard design would have been is practically impossible.
iii. Choosing steel from lower GWP suppliers is practical, but given the global trade in steel, would achieve no additional reductions; it would just shift California’s purchasing to the best performing steel mills while the same amount of output from bad performers would still reach the market, just used outside of California. This scenario would probably increase national or global shipping usage for steel as the lowest-cost way to achieve compliance, increasing overall GWP from the sector.
b. On the other hand, because most steel produced in the US and used in California is from Electric Arc Furnace (EAF) mills, getting the steel mills that sell products in California to purchase renewable energy would be a truly additional outcome of CARB’s regulation.
i. This is best accomplished by regulation – and hence reporting-- at the importer / distribution level, rather than at the project level, since there is no additionality to be achieved at the project level, while project-level reporting would increase construction costs and the industry is largely unprepared for it. One outcome of project-level reporting could be that every member of the construction supply chain would have to put in place a tracking (chain of custody) system to match each piece of steel to its mill of origin or EPD. While this would require a lot of work, it would not change the total impact of steel used for construction in California unless it creates a higher demand for low-GWP steel. But demand for low-GWP steel can be created by placing a requirement on importers and distributors, who can then allocate the total amount of steel (and its GWP) to projects as cost-effectively as possible through standard market mechanisms.
ii. This requires assessing the GWP of stage A1 of the lifecycle for steel products. A1 reporting may not be needed for all products (e.g. likely not significant for wood), but for steel A1 reporting is essential as A1 represents the area in which regulation can be effective in actually reducing GWP.

3. Wood
a. The biggest opportunity for reducing GWP of wood production is likely in design optimization. While optimization can be very hard to define in general (e.g. for steel, as noted above), light-framed wood construction is largely conducted under prescriptive structural codes that make a prescriptive baseline for wood uniquely possible. Against this baseline, improved practices could be used as the central focus of regulation, as improved practices are known within the industry but far from universally in use.
i. Improved practices include requiring 24” on center framing instead of 16” framing, 2-stud corners instead of 3 studs, avoided duplication of studs around window openings, etc. (These techniques are sometimes referred to as “advanced framing” or “optimized framing;” many also reduce the thermal conductivity of exterior walls, saving energy and GWP in building operation.)
ii. Requiring use of these techniques would avoid baseline questions like how big a residential baseline unit should be, which are difficult if not impossible to answer.
iii. These techniques are also practical to inspect for on a job site, and most if not all building officials are familiar with standard framing techniques and would be able to spot the differences easily.
b. Reporting for wood under this optimization approach would take place at the project level, but to be cost-effective could be inspection-based and would use readily available quantities to estimate wood volume reduction – e.g. square footage, linear feet of wall, number of windows and doors. (Because of overage in purchase and off-cuts in construction, determining the actual installed wood volume at high level of precision from purchase invoices is not practical.)
c. An additional strategy aimed at getting wood mills to electrify and purchase renewable energy could also be implemented. This should be implemented and reported at the mill level, with the same benefits and considerations as with the steel mill recommendations above and would be complementary to the recommended optimization strategy.

More generally, I would recommend that CARB go to the legislature to ask for authorization to fulfill its mandate through collaboration with BSC, other state agencies, and local building and public works departments, in order to maximize the cost-effective use of public resources and deliver a coordinated statewide approach to building industry partnership and regulation.

4. To the degree that CARB requires project-level reporting or compliance, it should work through local building departments. An investment from CARB in improving and harmonizing building permits across the state would be a good demonstration of “Abundance” thinking, creating value and streamlining what is often a cumbersome process today with a confusing amount of variation between jurisdictions. Harmonization would make embodied carbon policy (and state building codes generally) more effective. On the other hand, creating a second set of permits for construction projects in California would be the opposite. Working through local building departments would also allow for ready enforcement of new embodied carbon rules, conserving public resources and upskilling local agencies and staff. The California Energy Commission writes the Energy chapter of the state building Code, and it is enforced through local building departments; it would seem that CARB could ask for authority to do the same for embodied carbon.

5. CARB should also coordinate its requirements with CALGreen code section 5.409 on Life Cycle Assessment and low GWP materials. Much of what CARB wants projects to do is already starting to be required by the Building Standards Commission; requiring applicants to submit similar but different things to two different agencies could be confusing and also risks duplication of effort. As noted above, if CARB could work through the Building Code, it could increase its impact by spending its resources training building officials to enforce these sections instead of creating a duplicative parallel structure.

Thank you for your attention to these comments, and for your work to help our building industry reduce its emissions. I would be happy to make myself available for further conversation to assist CARB in making its implementation of AB2446 and AB43 as practical, impactful, and cost-effective as possible.

Sincerely yours,

Raphael Sperry, AIA, LEED AP, ENV SP