Washington Administrative Code

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.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40250, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-40250, filed 2/1/13, effective 7/1/13.]

[Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40260, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-40260, filed 2/1/13, effective 7/1/13.]

[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 …

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40325, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40325, filed 1/19/16, effective 7/1/16. Sta…

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40326, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40326, filed 1/19/16, effective 7/1/16. Sta…

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40327, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40327, filed 1/19/16, effective 7/1/16. Sta…

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40328, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40328, filed 1/19/16, effective 7/1/16. Sta…

[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapter 19.27 RCW. WSR 19-24-040, § 51-11C-40329, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW 19.27A.025, 19.27A.160, and 19.27.074. WSR 16-03-072, § 51-11C-40329, filed 1/19/16, effective 7/1/16. Sta…

C403.3 Equipment selection. Heating and cooling equipment installed in mechanical systems shall be sized in accordance with Section C403.3.1 and shall not be less efficient in the use of energy than as specified in Section C403.3.2.[Statutory Authority: RCW 19.27A.020, 19.27A.025…

C403.3.1 Equipment and system sizing. The output capacity of heating and cooling equipment shall be not greater than that of the smallest available equipment size that exceeds the loads calculated in accordance with Section C403.1.2. A single piece of equipment providing both hea…

C403.3.2 HVAC equipment performance requirements. Equipment shall meet the minimum efficiency requirements of Tables C403.3.2(1) through C403.3.2(16) when tested and rated in accordance with the applicable test procedure. Plate-type liquid-to-liquid heat exchangers shall meet the…

Table C403.3.2(1)Minimum Efficiency Requirements—Electrically Operated Unitary Air Conditioners and Condensing Unitsc,dEquipment TypeSize CategoryHeating Section TypeSubcategory or Rating ConditionMinimum EfficiencyTest ProcedureaAir conditioners, air cooled< 65,000 Btu/hbAllSpli…

Table C403.3.2(2)Electrically Operated Air-Cooled Unitary Heat Pumps—Minimum Efficiency RequirementsEquipment TypeSize CategoryHeating Section TypeSubcategory or Rating ConditionMinimum EfficiencyTest ProcedureaAir cooled (cooling mode) < 65,000 Btu/hAllSplit System, three phase …

Table C403.3.2(3)Water Chilling Packages—Minimum Efficiency Requirementsa,b,e,f Size Category Path APath BTest ProcedurecEquipment TypeUnitsFLIPLV.IPFLIPLV.IPAir-cooled chillers< 150 tonsEER(Btu/Wh)≥ 10.100≥ 13.700≥ 9.700≥ 15.800 ≥ 150 tonsEER(Btu/Wh)≥ 10.100≥ 14.000≥ 9.700≥ 16.1…

Table C403.3.2(4)Electrically Operated Packaged Terminal Air Conditioners, Packaged Terminal Heat Pumps, Single-Package Vertical Air Conditioners, Single-Package Vertical Heat Pumps, Room Air Conditioners and Room Air-Conditioner Heat Pumps—Minimum Efficiency RequirementseEquipme…

Table C403.3.2(5)Warm Air Furnaces and Combination Warm Air Furnaces/Air-Conditioning Units, Warm Air Duct Furnaces and Unit Heaters—Minimum Efficiency RequirementsEquipment TypeSize Category (Input)Subcategory or Rating ConditionMinimum Efficiencyd,cTest ProcedureaWarm-air furna…

Table C403.3.2(6)Gas- and Oil-Fired Boilers—Minimum Efficiency RequirementsEquipment TypeaSubcategory or Rating ConditionSize Category (Input)Minimum EfficiencyTest ProcedureaBoilers, hot waterGas-fired< 300,000 Btu/hg,h for applications outsidethe U.S.82% AFUEDOE 10 C.F.R. 430 A…

Table C403.3.2(7)Heat Rejection Equipment—Minimum Efficiency RequirementsiEquipment TypeaTotal System Heat Rejection Capacity at Rated ConditionsSubcategory or Rating ConditionhPerformanceRequiredb,c,d,f,gTest Procedurea,ePropeller or axial fan open-circuit cooling towersAll95°F …

Table C403.3.2(8)Electrically Operated Variable Refrigerant Flow Air Conditioners—Minimum Efficiency RequirementsbEquipment TypeSize CategoryHeating Section TypeSubcategory or Rating ConditionMinimum EfficiencyTest Procedurea < 65,000 Btu/hAllVRF Multi-Split System13.0 SEER VRF A…

Table C403.3.2(9)Electrically Operated Variable Refrigerant Flow Air-to-Air and Applied Heat Pumps—Minimum Efficiency RequirementsbEquipment TypeSize CategoryHeating Section TypeSubcategory or Rating ConditionMinimum EfficiencyTest Procedurea < 65,000 Btu/hAllVRF Multi-Split Syst…

C403.3.3 Hot gas bypass limitation. Cooling systems shall not use hot gas bypass or other evaporator pressure control systems unless the system is designed with multiple steps of unloading or continuous capacity modulation. The capacity of the hot gas bypass shall be limited as i…

C403.3.4Boiler requirements.Boiler systems shall comply with Sections C403.3.4.1 through C403.3.4.5.2.C403.3.4.1 Combustion air positive shut-off. Combustion air positive shut-off shall be provided on all newly installed boiler systems as follows:1. All boiler systems with an inp…

C403.3.5 Dedicated outdoor air systems (DOAS). For buildings with occupancies as shown in Table C403.3.5, outdoor air shall be provided to each occupied space by a dedicated outdoor air system (DOAS) which delivers 100 percent outdoor air without requiring operation of the heatin…

C403.3.6 Ventilation for Group R-2 occupancy. For all Group R-2 dwelling and sleeping units, a balanced ventilation system with a heat recovery system shall provide outdoor air directly to all habitable spaces. The heat recovery system shall have a 60 percent minimum sensible rec…

C403.3.7 Hydronic system flow rate. Chilled water and condenser water piping shall be designed such that the design flow rate in each pipe segment shall not exceed the values listed in Table C403.3.7 for the appropriate total annual hours of operation. Pipe sizes for systems that…

C403.3.8 Hydronic coil selection. Hydronic coils shall comply with Sections C403.3.8.1 and C403.3.8.2.EXCEPTION:Replacement coils within existing equipment.C403.3.8.1 Chilled-water coil selection. Chilled-water cooling coils shall be selected to provide a 15°F or higher temperatu…