Washington State Energy Codes: A Comprehensive Guide Key Changes in the 2024 Washington State Energy Codes Navigate: Washington Building Codes  The 2024 update to the WSEC introduces features several critical features and changes: Mandatory Heat Pump Heating: All new single-family homes, townhomes, and multi-family buildings up to three stories must include heat pump heating systems. This mandate applies statewide, with exceptions for rural areas lacking electricity access. Heat P...