WSEC 2021 energy compliance analysis

What code applies

Renton adopts the Washington State Energy Code (WSEC 2021, WAC 51-11R) as the statewide standard — effective March 15, 2024. There is no WSEC 2024 edition. No Renton-specific local amendments to the alteration provisions have been found; Washington State statute makes WSEC both the maximum and minimum energy code, which constrains city-level amendments.

Renton is in Climate Zone 4C (Marine).

What the analysis covers

Under WSEC 2021 Section R503 (alterations): building envelope assemblies that are part of the alteration must comply with the R-value requirements in R402.1.3 or R402.1.5. Additions greater than 500 sf of heated floor area are subject to full energy code requirements under Section R502.

The WSU Energy Program publishes a dedicated WSEC-R 2021 Alterations & Remodels compliance form that Washington building departments use to document remodel energy compliance. Ask Renton CED at the pre-application meeting whether a third-party energy rater is required for your project or whether contractor self-certification on the WSU WSEC-R worksheet is accepted.

Two compliance paths

• Prescriptive path. Each component (wall, roof, window, equipment) meets the table value in the code. Documented with the WSU compliance form.
• Performance path (REScheck). Trade-offs allowed across components — useful when one existing component can't be upgraded without cost-prohibitive work.

Why this happens during design, not later

If the energy analysis discovers the existing house has to be re-insulated or the heating system replaced as a condition of the alteration, that scope affects every later number — bid, schedule, PSE coordination. Settling it during design keeps the budget honest.