Mill Creek Building Department

WSEC-R 2021 energy code compliance resources for builders and contractors in Mill Creek, Snohomish County.

Building Department

Mill Creek Community Development

Last verified: 2026-04-19

Code environment

Climate Zone

CZ4

Western WA — moderate climate requirements.

Radon Zone

Zone 2

Moderate potential — mitigation recommended.

Ready to check your compliance?

wsec.ai generates a complete R406 credit summary you can submit with your permit application to Mill Creek Community Development.