Significant changes to residential provisions of the 2021 Washington State energy Code
Effective March 15, 2024
The state building and energy codes are updated every three years statewide. The 2021 Washington State Energy Code (WSEC) will be effective statewide on March 15, 2024 (delayed from July 1, 2023 and October 29, 2023).
The originally published code text of residential provisions of the 2021 WSEC can be found online on the State Building Code Council website. However, some provisions of the energy code are undergoing additional changes and are not yet finalized.
Learn more about the significant changes to the residential provisions of the energy code:
Overview (in development)
Heating & Cooling Systems (in development)
Water Heating (in development)
Additional Energy Efficiency Credits (in development)
King County energy code changes
Effective January 1, 2023
Consistent with King County’s Strategic Climate Action Plan, the King County Council has approved advanced energy code provisions beyond those provided by the Washington State Energy Code external link . The county amendments include the following:
Multifamily buildings with 4 or more stories and all commercial buildings
- Requirements for improved window thermal performance
- Prohibition of fossil fuel and electric resistance heating in most cases
- A requirement to use heat pump water heaters for multifamily buildings with central hot water service
- An increase in the number of required efficiency package credits
- A requirement to install solar panels or other on-site renewable energy
The full code text of these amendments can be found in King County Code Title 16.
Single family buildings, duplexes, and townhouses
- Solar-ready provisions
The full code text of solar-ready provisions can be found in 2018 International Residential Code (IRC) Appendix T external link (Washington State Legislature website)
For more information
- Learn about significant changes for commercial and multifamily buildings on our Energy code update handout
- Learn about the solar-ready provisions for single-family buildings on our Solar-ready provisions handout
At the state level, adoption of the 2021 International Energy Conservation Code (IECC) with state amendments is currently under consideration. Adoption is expected to be effective on July 1, 2023.
Washington State adopted the 2018 Washington State Energy Code—which is the 2018 International energy Conservation Code with amendments—effective on Feb. 1, 2021.
This code regulates elements of new and existing buildings related to energy use, including:
- Building envelope
- Mechanical systems
- Water heating and distribution
The 2018 Washington State Energy Code is divided into Commercial and Residential provisions.
Commercial provisions apply to:
- Non-residential buildings
- Multifamily buildings of four or more stories
Residential provisions apply to:
- Single family homes
- Multifamily buildings of three or fewer stories
Federal tax credit for solar photovoltaics
The federal solar energy tax credit has increased! The Inflation Reduction Act expanded the tax credit to 30% of a solar energy system’s value. Learn about the recent changes and check this Department of Energy website external link to find out if you’re eligible to claim the credit.
Continuously burning pilot lights prohibited on gas fireplaces
Beginning September 1, 2022, gas fireplaces installed in Washington State may not have continuously burning pilot lights.
To reduce energy waste, the State Building Code Council (SBCC) adopted law that prohibits these types of pilot lights, which are also known as “standing” pilot lights. This prohibition is already in effect for other types of equipment, including furnaces, cooking appliances, pool heaters, and spa heaters. Newer technologies that replace standing pilot lights will both reduce the energy used by the appliance and save homeowners money on their utility bills.
This rule was originally intended to go into effect on February 1, 2021. The SBCC delayed it for 19 months because supply chain problems made it hard to get equipment that meets the new rule.
Support and compliance forms for energy code are available from:
Washington State University Energy Program external link
(residential provisions only)
- Send email
- Phone: 360-956-2042
Washington State Energy code Commercial Technical Support external link
(commercial provisions only)
- Send email
- Phone: 360-539-5300
Beyond energy code minimums
- King County’s Green Building Handbook and green sheets will help you make decisions that will save energy and reduce costs.
- King County’s GreenTools program is designed to help anyone in King County green their built environment while addressing critical environmental issues like global warming, habitat restoration, solid waste reduction, and community planning. GreenTools provides technical assistance, hands-on training, and policy development through community partnerships in the public and private sectors.