This bill adds new sections to chapter 19.27 RCW and one to chapter 43.330 RCW to require embodied carbon emissions reductions for large building projects and to create related reporting and rulemaking processes. It applies to new construction, additions, and renovations of 100,000 square feet or larger covered by the International Building Code, excluding school district construction. The State Building Code Council (SBCC) must adopt rules to implement the requirements and may consult specified state agencies, the University of Washington, an existing technical work group, and other parties. Projects may comply by one of three pathways: reuse at least 45% of an existing structure and envelope (with limits on added area), demonstrate reductions in life-cycle stages A1–A3 for project-wide covered products using productand facility-specific environmental product declarations (EPDs) for at least 90% of covered products, or demonstrate reductions using a whole building life-cycle assessment (WBLCA) compared to a functionally equivalent reference building. The design professional of record (a licensed architect or engineer) must perform calculations, update them based on procured products, and attest to their accuracy with a stamped letter before substantial completion, and must enter required data into a public database maintained by the Department of Commerce. The Department of Commerce must create and maintain a public database and website with reporting forms, guidance, templates, and a list of acceptable software, and must conduct random audits of 3% of projects each year; audit findings do not create penalties. The bill sets code-cycle timelines: product/facility EPDs or WBLCA results and reporting are required for covered products in the 2024 code cycle, an industry-regional EPD is required if product/facility-specific EPDs are unavailable before 2027, and the SBCC must adopt more stringent codes in the 2027 and 2030 cycles. Construction permitted under the 2030 code must achieve a 30% reduction in embodied carbon emissions either from a project-wide static baseline (using Carbon Leadership Forum 2023 material baselines or comparable averages determined by the council) or compared to the reference building. The SBCC must report progress by December 31, 2028, and every three years thereafter; the Department of Commerce must report major database and audit findings on the same schedule. This is a procedural and regulatory change establishing new compliance pathways, reporting duties, modeling and certification requirements, and agency duties; it does not create a new crime or impose criminal penalties. Several important details are not specified in the provided text: the bill refers to "covered products" but does not define them here, the method for calculating the referenced "industry average" and the basis for the 90% threshold (for example by cost, mass, or volume) is left to SBCC rulemaking, the "project-wide static baseline" is not defined in this extract, the contents of the external standards and data sources cited are not included, and the bill text as provided contains an internal subsection numbering inconsistency and does not describe the technical work group's composition.

If enacted, large building projects (new construction, additions, or renovations 100,000 sq ft or larger, excluding school district projects) will face new requirements to show they cut "embodied carbon" either by reusing much of an existing structure, by using productand facility-specific environmental product declarations (EPDs) to show lower A1–A3 impacts for most covered products, or by doing a whole-building life-cycle assessment compared to a reference building. That means architects and engineers must do extra calculations, get or update EPDs, run or hire WBLCA work, enter results into a public system maintained by the Department of Commerce, and formally attest with a stamped letter before substantial completion. Projects may need different materials, more reuse, or added modeling costs to meet the 2030 target of roughly a 30% reduction, and audit risk exists (Commerce will randomly audit about 3% of projects annually) though audits do not trigger penalties. State agencies will take on new rulemaking, reporting, and oversight tasks: the State Building Code Council must adopt rules, define covered products and baselines, and phase in targets in the 2027 and 2030 code cycles, while Commerce must build and run a public database, produce guidance and training, and report progress starting in 2028. Practical impacts depend on several items left to rulemaking—what exactly counts as "covered products," how the 90% product threshold and industry averages are calculated, and how the "project-wide static baseline" is defined—so project costs and compliance choices will vary until those details are set.