Residential Energy Code Compliance for Mercer Island
***The 2021 CODE UPDATES ARE EFFECTIVE MARCH 15, 2024***
Single Family – New & Additions
Single-family project will use one of three options provided by the Washington State Energy Code.
Single Family Prescriptive Worksheet 2021
Single Family Prescriptive Worksheet 2018
Each dwelling unit in a residential building shall comply with sufficient options from Table R406.2 (fuel normalization credits) and Table 406.3 (energy credits) to achieve the following minimum number of credits. To claim this credit, the building permit drawings shall specify the option selected and the maximum tested building air leakage, and show the qualifying ventilation system and its control sequence of operation.
*Please include selected credits on the Cover sheet and Permit set
Credit Selection Requirements - Varies On Size of Project and Scope
The most commonly selected compliance method at the city of mercer island is the energy credit selection, a summary of the requirements are below.
| Additions less than 500 square feet: | 2 credits Additions 150 square feet to 500 square feet. |
| Small Dwelling Unit: |
5 credits
|
| Medium Dwelling Unit: | 8 credits All dwelling units that are not included in Small or Large or addition. |
| Large Dwelling Unit: | 9 credits Dwelling units exceeding 5,000 sf of conditioned floor area |
| Additions less than 500 square feet: | 1.5 credits Additions less than 500 square feet: |
| Small Dwelling Unit: | 3 credits Dwelling units less than 1,500 sf in conditioned floor area with less than 300 sf of fenestration area. Additions to existing building that are greater than 500 sf of heated floor area but less than 1,500 sf. |
| Medium Dwelling Unit: | 6 credits All dwelling units that are not included in Small or Large |
| Large Dwelling Unit: | 7 credits Dwelling units exceeding 5,000 sf of conditioned floor area |
Building Assembly Assistance - Details
To assist with 2021 energy code construction detailing: IECC - created references that may help designers, homeowners, or contractors with detailing compliance in the energy code.
Site-Specific - Building Assemblies (For Reference)
*Note these details are not screened for code compliance in Mercer Island, and are for reference and convenience of our applicants. For Project-Specific Building Assemblies: Coordination between your engineer, architect, or site may be required.
Builders Field Guide to Energy Code
Washington State University - Energy Code Guide
- Note: Mercer Island Is not affiliated with WSU.
- If your building permit was submitted after March 15, 2024, it must meet requirements of 2021 WSEC-R
- If your building permit was submitted before February 1, 2021, it must meet requirements of 2015 WSEC-R
- *The Content of this page does not supersede the code.
