2018 Washington State Energy Code

New to the energy code? Please read this.


The State Building Code Council voted on May 24, 2023, to delay the effective date of the 2021 codes for 120 days, which changed the effective date from July 1, 2023 to October 29, 2023. On September 15, 2023, the State Building Code Council agreed on another delay. The new effective date for all building codes is March 15, 2024.

The Council is also entering rulemaking to modify sections in the commercial and residential energy codes to address legal uncertainty stemming from the decision in California Restaurant Association v. City of Berkeley recently issued by the Ninth Circuit Court of Appeals.


Our energy code team provides support to those who use the residential sections of the Washington State Energy Code (WSEC-R).

For assistance and updates:

2021 WSEC-R Training

2021 WSEC-R Forms and Documents

Please use the updated documents for the WESC-R Codes for your testing and code certificates needed for final Certificate of Occupancy (C of O).

See below for instructions on how to utilize the code compliance documents and tools.

2018 WSEC-R Training Opportunities

Please review training opportunities on various energy code compliance topics and duct testing before working on your permit application documents.

Questions About Commercial Portions of the WSEC?

Contact Evergreen Technology Consulting at 360-539-5300 or email com.techsupport@WAenergycodes.com. If your project is a mixed use building, please contact Evergreen prior to working on residential low-rise R2 units.

2018 WSEC-Commercial

Permit Application Documents

Right-click the form name and save it to your computer so you can use the form's automated functions.

Options for Code Compliance

Prescriptive Method

The prescriptive path is the typical compliance approach. To follow this approach, you will need to complete a prescriptive worksheet, glazing schedule, and heating system sizing calculator.


  1. NEW Energy Option 3.5.2 per this SBCC emergency rule. Option 3.5.2 applies to single-family homes and allows air-source, inverter-driven, centrally ducted heat pumps with minimum HSPF of 10.0 as long as other conditions are met. The Single-Family Prescriptive worksheet has been updated to include this option. 
  2. Table R406.2 in 2018 WSEC-Residential references two tables that are provided in 2018 WSEC-Commercial: Table C403.3.2(1)C and C403.3.2(2). These tables are copied here for your convenience.
  3. Table 406.3, Option 2, in 2018 WSEC-Residential references section numbers in the 2018 IRC and IMC that are no longer accurate. We will update our prescriptive worksheets and the Code Compliance Calculator soon to reflect these changes. In the meantime, here are the updated section numbers:
    • IRC 2015 Section M1507.3 Whole-House Mechanical Ventilation System corresponds to IRC 2018 Section M1505.4 Whole-House Mechanical Ventilation System
    • IMC 2015 Section 403.8 Ventilation Systems for Group R Occupancies corresponds to IMC 2018 Section 403.4 Group R Whole-House Mechanical Ventilation System

Prescriptive Worksheets

This approach is the simplest method of WSEC code compliance. A project complies with building envelope requirements if it meets all minimum insulation levels required.

One- and Two-Family Prescriptive Worksheet - All Climate Zones with Table 406: This worksheet is used for detached one- and two-family residences and multiple single-family residences (townhouses) and other IRC building types (IRC-WA Section R102.2, WBC Section 310).

Multifamily Prescriptive Worksheet - All Climate Zones with Table 406: This worksheet is used for Group R-2 buildings three stories or less in height above grade plane. Other Group R-2 buildings must comply with the commercial energy code.

Instructions for printing or emailing prescriptive worksheets

Prescriptive Checklist : This is a guide for those working to comply with the 2018 WSEC-R. It lists items that apply to most residential new construction projects but should not be viewed as a comprehensive list of code requirements.

Code Compliance Calculator

The Code Compliance Calculator (C3) will help you document building designs for the 2021 and 2018 WSEC-R. It is especially useful for designs using the UA percent trade-off for Option 1 envelope measures (Section R402.3) and the Total UA Alternative (Section R402.1.5). C3 replaces the UA Alternative Worksheet (formerly referred to as the Component Performance worksheet) and integrates the glazing schedule and the heating system sizing worksheet. It also includes a ventilation calculator to determine whole house mechanical ventilation airflow rate per IRC and IMC, and a maximum allowable duct leakage calculator per RS-33. 

C3 requires Excel for Windows installed on your computer (not web-based) and is not available for Macs. If you do not need a UA trade-off or total UA alternative analysis, we recommend using the PDF prescriptive worksheets instead of C3 because they are simpler and compatible with most PDF software on PCs and Macs.

Disclaimer: Results from the C3 assume that all data is entered correctly and completely. Results do not constitute an official decision. Your analysis should be reviewed by your building official/authority having jurisdiction.

Code Compliance Calculator and readme

Glazing Schedule

Using the Prescriptive Method, all glazing must have an “area weighted average” U-Factor of 0.30. This means that some windows can have a higher U-factor than 0.30 and some can have a lower U-factor than 0.30, as long as the area weighted average is U-0.30 or lower. You may need to complete this form to document glazing compliance when applying for your building permit. It is useful to have tested values when filling out this forms. NFRC AMMA provides custom U-values.

Glazing Schedule

Heating System Sizing

We recommend you use the HVAC Sizing Tool from BetterBuiltNW, which is based on Manual J.

The previous Heating System Sizing Worksheet may be useful only if you do not have cooling. This calculator assumes that your glazing products have an area weighted average of U-0.30. Choose insulation levels and enter the areas of each building component. Hover your cursor over the red triangles to see the embedded help notes. An instruction sheet is also provided.

Heating System Sizing Worksheet

Heating System Sizing Instructions

Duct Testing Documentation

Duct Testing Affidavit (New Construction)

Duct Testing Affidavit (Existing Construction)

Alterations (Remodel) Worksheet

Requirements for alterations or remodels of existing structures differ from the requirements for new construction. When doing a combined addition and remodel, use the Alteration (Remodel) Worksheet for the remodeling portion and the Prescriptive Worksheet for the new portion. No credits from Table 406.2 are required and existing buildings are not necessarily required to meet all of the energy code requirements.

Alterations (Remodel) Worksheet


Compliance Certificate

The certificate should be completed by the builder or other approved party and posted in the space where the furnace is located, a utility room, or another approved location in the building.

2018 WSEC Compliance Certificate

2018 Compliance Certificate - Instructions

Insulation Certificate for Residential New Construction

Insulation Certificate

Technical Assistance and Testing Resources

Duct Testers

This list of duct testers includes individuals who attended the one-day duct testing training offered by the WSU Energy Program or completed the online training and meet the minimum requirements to test ducts for the WSEC. If you are interested in being certified as a duct tester by the WSU Energy Program, please see the Duct Testing and Design information on our Training Opportunities webpage.

Technicians who can verify that they have successfully completed duct testing training provided by the Northwest ENERGY STAR Program or Performance Tested Comfort Systems (PTCS) may also be qualified to test ducts under the WSEC.

Home Energy Raters (HERS)

For information about Home Energy Raters, see the Building Efficiency webpage.

2021 WSEC-R Resources

Training Opportunities

Forms and Documents

2018 WSEC-R Resources

Training Opportunities

Permit Application Documents

Tech Assistance & Testing Resources

Additional Resources 

WSU Energy Code FAQs;

Relationship with SBCC

The WSEC-R team is not an affiliate of, nor do we speak for, the Washington State Building Code Council (SBCC). Official opinions of WSEC intent are made only by the SBCC in response to official inquiries submitted to SBCC by authorities having jurisdiction (AHJ). While we try to stay aligned with SBCC, the technical support we provide is advisory only and non-binding on AHJ, builders, designers, and building trades personnel who build or remodel residential structures. Please contact the State Building Code Council to discuss concerns about the new code.