Which states are still on older building codes?

A clean cross-state comparison is only honest if it is loud about what it cannot compare. Across the three codes, 39 of 153state-code cells have no single comparable statewide edition, so we show the source's verbatim description and mark them unknown instead of forcing a year. The reasons cluster:

• State-developed standards.California (Building Energy Efficiency Standards, Title 24), Florida, Oregon, Washington, and Vermont run their own energy codes that do not map to a single IECC edition. Calling any of them "IECC 20xx" would be wrong.
• Code-by-reference. Some states adopt the energy provisions through the IRC's Chapter 11 rather than a standalone IECC edition, so there is no clean standalone IECC year to report.
• Local amendments (home rule).Where the practical answer is set by a city — New York City's own electrical and construction codes, the District of Columbia's DC-specific editions — a statewide label would mislead. We flag the amendment and keep the verbatim description.
• No single statewide effective date. A handful of states leave adoption to local jurisdictions or had no one clean statewide date in the public record. We report that rather than invent one.

By code, that is 8 unknown for the NEC, 14 for the IRC, and 17for the IECC — the energy code, predictably, has the most. These rows are excluded from the distribution and from the "editions behind" arithmetic entirely.

• Source. ProFix Directory editorial compilation of public state building-code adoption status, cross-checked against the NFPA NEC enforcement maps (NFPA 70) and the International Code Council I-Code adoption maps (IRC, IECC). Read live from the committed seed data/seed/state-code-updates-2026.json — the same dataset behind the per-state code-update pages — as of 2026-06-08. ProFix-published open data, CC-BY-4.0.
• We never guess an edition. A numeric edition year is parsed only from an unambiguous "<CODE> <YYYY>" string. Every state-developed standard, code-by-reference pointer, locally amended set, or missing statewide date is classified as unknown and shown with its verbatim source description — never coerced to a year.
• "Behind by N editions" is arithmetic, framed as permitting context. It is the latest published edition (NEC 2023, IRC 2024, IECC 2024) minus the adopted edition. It describes which rulebook a permit office enforces and which provisions apply to a project — it is never a statement that a state is unsafe. An older adopted code is still a complete, enforced, legal standard.
• The NEC baseline is 2023, and we say why. NFPA published NEC 2026 in early 2026, but statewide adoption of it is only just beginning and no state in this dataset is on it yet, so NEC 2023 is the honest comparison baseline. IRC and IECC use the 2024 I-Codes, the current ICC model editions (published 2024-08-14).
• This is a cross-state comparison, not per-state prose.The detailed narrative of what each code change means for one state's contractors and homeowners lives on the /code-update pages; this study is the machine-readable matrix across all of them.
• Aggregate only, computed live. The summary is a per-state regulatory matrix — editions and counts — with no contractor, permit, or address anywhere. Every number is read from the seed at render time, so the study updates automatically when a state re-adopts; nothing here is hardcoded.