Chapter 51-11C State Building Code adoption and amendment of the 2021 edition of the International Energy Conservation Code, Commercial.

Table C303.1.5U-Factors for Spandrel Panels and Glass Curtain Walls Rated R-Value of Insulation Between Framing MembersNoneR-4R-7R-10R-15R-20R-25R-30Frame TypeSpandrel Panel ABCDEFGHAluminum without Thermal BreakSingle glass pane, stone or metal panel10.3600.2420.2220.2120.2030.1…

C303.2 Installation. Materials, systems and equipment shall be installed in accordance with the manufacturer's instructions and the International Building Code.C303.2.1 Protection of exposed foundation insulation. Insulation applied to the exterior of basement walls, crawlspace w…

[Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-40000, filed 2/1/13, effective 7/1/13.]Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency.

C401.1 Scope. The provisions in this chapter are applicable to commercial buildings and their building sites.C401.2 Application. Commercial buildings shall comply with the fossil fuel compliance path according to Section C401.3, or with one of the following:1. Prescriptive compli…

[Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-40200, filed 2/1/13, effective 7/1/13.]

C402.1 General. Building thermal envelope assemblies for buildings that are intended to comply with the code on a prescriptive basis, in accordance with the compliance path described in Item 1 of Section C401.2, shall comply with the following:1. The opaque portions of the buildi…

C402.1.1Low energy buildings, semi-heated buildings and greenhouses. Low energy buildings shall comply with Section C402.1.1.1. Semi-heated buildings and spaces shall comply with Section C402.1.1.2. Greenhouses shall comply with Section C402.1.1.3.C402.1.1.1 Low energy buildings.…

C402.1.2 Equipment buildings. Buildings that comply with all of the following shall be exempt from the building thermal envelope provisions of this code:1. Are separate buildings with floor area no more than 500 square feet (50 m2).2. Are intended to house electric equipment with…

Table C402.1.3Opaque Thermal Envelope Insulation ComponentMinimum Requirements, R-value Methoda, jCLIMATE ZONE5 AND MARINE 4 All OtherGroup RRoofsInsulation entirely above deckR-38ciR-38ciMetal buildingsbR-25 + R-22 LSR-25 + R-22 LSAttic and otherR-49R-49Walls, Above GradeiMasshR…

C402.1.3 Insulation component R-value-based method.Building thermal envelope opaque assemblies shall comply with the requirements of Section C402.2 based on the climate zone specified in Chapter 3. For opaque portions of the building thermal envelope intended to comply on an insu…

C402.1.4 Assembly U-factor, C-factor, or F-factor-based method. Building thermal envelope opaque assemblies shall meet the requirements of Section C402.2 based on the climate zone specified in Chapter 3. Building thermal envelope opaque assemblies intended to comply on an assembl…

Table C402.1.4Opaque Thermal Envelope Requirementsa,fCLIMATE ZONE5 AND MARINE 4 All OtherGroup RRoofsInsulation entirely above deckU-0.027U-0.027Metal buildingsU-0.031U-0.031Attic and otherU-0.021U-0.021Joist or single rafterU-0.027U-0.027Walls, Above GradekMassd,gU-0.104U-0.078M…

Table C402.1.4.2Effective R-values For Steel Stud Wall AssembliesNOMINAL STUD DEPTH (inches)SPACING OF FRAMING (inches)CAVITYR-VALUE (insulation)CORRECTION FACTOR (Fc)EFFECTIVER-VALUE (ER)(Cavity R-Value × Fc) 3 1/216130.465.98 150.436.45 3 1/224130.557.15 150.527.80 616190.377.0…

C402.1.5 Component performance alternative. Building envelope values and fenestration areas determined in accordance with Equation 4-2 shall be permitted in lieu of compliance with the U-factors and F-factors in Table C402.1.4 and C402.4 and the maximum allowable fenestration are…

C402.2 Specific building thermal envelope insulation requirements. Insulation in building thermal envelope opaque assemblies shall comply with Sections C402.2.1 through C402.2.9 and Table C402.1.3.Where this section refers to installing insulation levels as specified in Section C…

C402.2.1Roof assembly. The minimum thermal resistance (R-value) of the insulating material installed either between the roof framing or continuously on the roof assembly shall be as specified in Table C402.1.3, based on construction materials used in the roof assembly.EXCEPTIONS:…

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapters 19.27A and 19.27 RCW. WSR 22-14-091, 23-12-101, and 23-20-021, § 51-11C-402211, filed 7/1/22, 6/7/23, and 9/25/23, effective 3/15/24. Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter …

C402.2.2 Above-grade walls. The minimum thermal resistance (R-value) of materials installed in the wall cavity between the framing members and continuously on the walls shall be as specified in Table C402.1.3, based on framing type and construction materials used in the wall asse…

C402.2.3 Floors. The thermal properties (component R-values or assembly U- or F-factors) of floor assemblies over outdoor air or unconditioned space shall be as specified in Table C402.1.3 or C402.1.4 based on the construction materials used in the floor assembly. Floor framing c…

C402.2.4 Slabs-on-grade. The minimum thermal resistance (R-value) of the insulation for unheated or heated slab-on-grade floors designed in accordance with the R-value method of Section C402.1.3 shall be as specified in Table C402.1.3.C402.2.4.1 Insulation installation. Where ins…

C402.2.5 Below-grade walls. The R-value of the insulating material installed in, or continuously on, the below-grade walls shall be in accordance with Table C402.1.3. The U-factor or R-value required shall extend to the level of the lowest floor of the conditioned space enclosed …

C402.2.6 Insulation of radiant heating systems.Radiant heating system panels, and their associated components that are installed in interior or exterior assemblies shall be insulated to an R-value of not less than R-3.5 on all surfaces not facing the space being heated. Radiant h…

C402.2.7 Airspaces. Where the R-value of an airspace is used for compliance in accordance with Section C401.2, the airspace shall be enclosed in an unventilated cavity constructed to minimize airflow into and out of the enclosed airspace. Airflow shall be deemed minimized where t…

C402.2.8 Above-grade exterior concrete slabs. Above-grade concrete slabs that penetrate the building thermal envelope including, but not limited to, decks and balconies, shall each include a minimum R-10 thermal break, aligned with the primary insulating layer in the adjoining wa…

C402.2.9 Vertical fenestration intersection with opaque walls.Vertical fenestration shall comply with Items 1, 2, and 3, as applicable.1. Where wall assemblies include continuous insulation, the exterior glazing layer of vertical fenestration and any required thermal break in the…

C402.3 Reserved.C402.4 Fenestration. Fenestration shall comply with Sections C402.4 through C402.4.4 and Table C402.4. Daylight responsive controls shall comply with this section and Section C405.2.5.[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapters 19.27A…

Table C402.4Building Envelope Fenestration Maximum U-factor and SHGC RequirementsCLIMATE ZONE5 AND MARINE 4U-factor for Class AW windows rated in accordance with AAMA/CSA101/I.S.2/A440, vertical curtain walls and site-built fenestration productsaFixedbU-factorU-0.34OperablecU-fac…

C402.4.1 Maximum area. The total building vertical fenestration area (not including opaque doors and opaque spandrel panels) shall not exceed 30 percent of the total building gross above-grade wall area. The skylight area shall not exceed 5 percent of the total building gross roo…

C402.4.2 Minimum skylight fenestration area. Skylights shall be provided in enclosed spaces that meet all the following criteria:1. Floor area of enclosed spaces is greater than 2,500 square feet (232 m2).2. Space is located directly under a roof and have a ceiling height greater…

C402.4.3 Maximum U-factor and SHGC. The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4.The window projection factor shall be determined in accordance with Equation 4-6.PF = A/B(Equation 4-6)Where: PF=Projection facto…

C402.4.4 Doors. Opaque doors shall be considered part of the gross area of above-grade walls that are part of the building thermal envelope, including the frame. Opaque doors shall comply with Table C402.1.4. Other doors shall comply with the provisions of Section C402.4.3 for ve…

C402.5 Air leakage-thermal envelope. The thermal envelope of buildings shall comply with Sections C402.5.1 through C402.5.8.[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40240, filed 11/26/19, effective 7/1/20. Statuto…

C402.5.1 Air barriers. A continuous air barrier shall be provided throughout the building thermal envelope. The continuous air barriers shall be located on the inside or outside of the building thermal envelope, located within the assemblies composing the building thermal envelop…

C402.5.5 Rooms containing fuel-burning appliances. Where combustion air is supplied through openings in an exterior wall to a room or space containing a space conditioning fuel-burning appliance, one of the following shall apply:1. The room or space containing the appliance shall…

C402.5.6 Doors and access openings to shafts, chutes, stairways, and elevator lobbies. Doors and access openings from conditioned space to shafts, chutes, stairways and elevator lobbies shall be gasketed, weatherstripped or sealed.EXCEPTIONS:1. Door openings required to comply wi…

C402.5.7 Air intakes, exhaust openings, stairways and shafts. Stairway enclosures, elevator shaft vents and other outdoor air intakes and exhaust openings integral to the building envelope shall be provided with dampers in accordance with Section C403.7.8.[Statutory Authority: RC…

C402.5.8 Loading dock weatherseals. Cargo door openings and loading dock door openings shall be equipped with weatherseals that restrict infiltration and provide direct contact along the top and sides of vehicles that are parked in the doorway.[Statutory Authority: RCW 19.27A.020…

C402.5.9 Vestibules. All building entrances shall be protected with an enclosed vestibule, with all doors opening into and out of the vestibule equipped with self-closing devices. Vestibules shall be designed so that in passing through the vestibule it is not necessary for the in…

C402.5.10 Recessed lighting. Recessed luminaires installed in the building thermal envelope shall be all of the following:1. IC rated.2. Labeled as having an air leakage rate of not more than 2.0 cfm (0.944 L/s) when tested in accordance with ASTM E 283 at a 1.57 psf (75 Pa) pres…

[Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-40300, filed 2/1/13, effective 7/1/13.]

C403.1 General. Mechanical systems and equipment serving heating, cooling, ventilating, and other needs shall comply with this section.EXCEPTIONS:1. Energy using equipment used by a manufacturing, industrial or commercial process other than for conditioning spaces or maintaining …

C403.1.4 Use of electric resistance and fossil fuel-fired HVAC heating equipment. HVAC heating energy shall not be provided by electric resistance or fossil fuel combustion appliances. For the purposes of this section, electric resistance HVAC heating appliances include, but are …

C403.2 System design. Mechanical systems shall be designed to comply with Sections C403.2.1 through C403.2.4. Where elements of a building's mechanical systems are addressed in Sections C403.3 through C403.13, such elements shall comply with the applicable provisions of those sec…

C403.2.1Zone isolation required. HVAC systems, DOAS and exhaust systems serving areas that are intended to operate or be occupied nonsimultaneously shall be divided into separate isolation areas. Zones intended to be occupied simultaneously may be grouped into a single isolation …

C403.2.2 Ventilation and exhaust.C403.2.2.1 Ventilation. Ventilation, either natural or mechanical, shall be provided in accordance with Chapter 4 of the International Mechanical Code. Where mechanical ventilation is provided, the system shall be configured to provide no greater …

C403.2.3 Fault detection and diagnostics. New buildings with an HVAC system serving a gross conditioned floor area of 100,000 square feet (9290 m2) or larger shall include a fault detection and diagnostics (FDD) system to monitor the HVAC system's performance and automatically id…

C403.2.4 Variable flow capacity. For fan and pump motors 5.0 hp and greater including motors in or serving custom and packaged air handlers serving variable air volume fan systems, constant volume fans, heating and cooling hydronic pumping systems, pool and service water pumping …