R503.1 General.Alterations to any building or structure shall comply with the requirements of the code for new construction, without requiring the unaltered portions of the existing building or building system to comply with this code. Alterations shall be such that the existing building or structure is no less conforming to the provisions of this code than the existing building or structure was prior to the alteration.
Alterations shall not create an unsafe or hazardous condition or overload existing building systems.
Alterations shall be such that the existing building or structure uses no more energy than the existing building or structure prior to the alteration. Alterations to existing buildings shall comply with Sections R503.1.1 through R503.2.
The code official may approve designs of alterations which do not fully conform to all of the requirements of this code where in the opinion of the code official full compliance is physically impossible and/or economically impractical and:
The alteration improves the energy efficiency of the building; or
The alteration is energy efficient and is necessary for the health, safety, and welfare of the general public.
R503.1.1 Building envelope. Building envelope assemblies that are part of the alteration shall comply with Section R402.1.3 or R402.1.5, Sections R402.2.1 through R402.2.10, R402.3.1, R402.3.2, R402.3.5, and R402.4.2.
EXCEPTION: | The following alterations need not comply with the requirements for new construction provided the energy use of the building is not increased: |
| 1. Storm windows installed over existing fenestration. |
| 2. Existing ceiling, wall or floor cavities exposed during construction provided that these cavities are filled with insulation. 2 x 4 framed walls shall be insulated to a minimum of R-15 and 2 x 6 framed walls shall be insulated to a minimum of R-21. |
| 3. Construction where the existing roof, wall or floor cavity is not exposed. |
| 4. Roof recover. |
| 5. Roofs without insulation in the cavity and where the sheathing or insulation is exposed during reroofing shall be insulated either above or below the sheathing. |
| 6. Surface-applied window film installed on existing single pane fenestration assemblies to reduce solar heat gain provided the code does not require the glazing fenestration to be replaced. |
R503.1.1.1 Replacement fenestration. Where some or all of an existing fenestration unit is replaced with a new fenestration product, including sash and glazing, the replacement fenestration unit shall meet the applicable requirements for U-factor and SHGC in Table R402.1.3. Where more than one replacement fenestration unit is being installed, an area-weighted average of the U-factor and SHGC of all replacement fenestration shall be permitted to be used to demonstrate compliance.
R503.1.2 Heating and cooling systems. New heating, cooling and duct systems that are part of the alteration shall comply with Section R403.
EXCEPTIONS: | 1. Where ducts from an existing heating and cooling system are extended, duct systems with less than 40 linear feet in unconditioned spaces shall not be required to be tested in accordance with Section R403.2.2. |
| 2. Existing duct systems constructed, insulated or sealed with asbestos. |
R503.1.3 Service hot water systems. New service hot water systems that are part of the alteration shall comply with Section R403.5.
EXCEPTION: | Replacement of water heating equipment shall not be required to comply with Section R403.5.5. |
R503.1.4 Lighting. New lighting systems that are part of the alteration shall comply with Section R404.1.
EXCEPTION: | Alterations that replace less than 10 percent of the luminaires in a space, provided that such alterations do not increase the installed interior lighting power. |
[Statutory Authority: RCW
19.27A.020,
19.27A.045,
19.27A.160, and chapter
19.27A RCW. WSR 24-03-084, § 51-11R-50300, filed 1/16/24, effective 3/15/24; WSR 23-02-060, 23-12-102, and 23-20-022, § 51-11R-50300, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24. Statutory Authority: RCW
19.27A.045 and chapter
19.27A RCW. WSR 20-21-081, § 51-11R-50300, filed 10/19/20, effective 2/1/21. Statutory Authority: RCW
19.27A.020,
19.27A.045,
19.27A.160 and chapter
19.27 RCW. WSR 20-01-047, § 51-11R-50300, filed 12/9/19, effective 7/1/20. Statutory Authority: RCW
19.27A.025,
19.27A.045,
19.27A.160, and
19.27.074. WSR 17-10-063, § 51-11R-50300, filed 5/2/17, effective 6/2/17. Statutory Authority: RCW
19.27A.020,
19.27A.045,
19.27A.160, and
19.27.074. WSR 16-02-127, § 51-11R-50300, filed 1/6/16, effective 7/1/16.]