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. The following buildings, or enclosed portions thereof, separated from the remainder of the building by building thermal envelope assemblies complying with this code shall be exempt from all thermal envelope provisions of this code:
1. Those that are heated and/or cooled with a peak design rate of energy usage less than 3.4 Btu/h × ft2 (10.7 W/m2) or 1.0 watt/ft2 (10.7 W/m2) of floor area for space conditioning purposes.
2. Those that do not contain conditioned space.
3. Unstaffed equipment shelters or cabinets used solely for personal wireless service facilities.
C402.1.1.2 Semi-heated buildings and spaces. The building envelope of semi-heated buildings, or portions thereof, shall comply with the same requirements as that for conditioned spaces in Section C402, except as modified by this section. The total installed output capacity of mechanical space conditioning systems serving a semi-heated building or space shall comply with Section C202. Building envelope assemblies separating conditioned space from semi-heated space shall comply with exterior envelope insulation requirements. Semi-heated spaces are not required to comply with the opaque wall insulation provisions of Section C402.2.3 for walls that separate semi-heated spaces from the exterior or low energy spaces. Fenestration that forms part of the building thermal envelope enclosing semi-heated spaces shall comply with Section C402.4. Semi-heated spaces shall be calculated separately from other conditioned spaces for compliance purposes.
Opaque walls in semi-heated spaces shall be calculated as fully code compliant opaque walls for both the target and proposed for the Target UA calculations for Component Performance compliance per Section C402.1.5, and for the Baseline Building Design for Total Building Performance compliance per Section C407. The capacity of heat trace temperature maintenance systems complying with Section C404.7.2 that are provided for freeze protection of piping and equipment only shall not be included in the total installed output capacity of mechanical space conditioning systems.
EXCEPTION: | Provided the total installed heating output capacity of mechanical space conditioning does not exceed the criteria for semi-heated space as defined in Section C202, a semi-heated building or space may comply with this section when served by heat pumps without electric resistance back up and connected to a heating only thermostat. |
C402.1.1.3 Greenhouses.Greenhouse structures or areas that comply with all of the following shall be exempt from the building envelope requirements of this code:
1. Exterior opaque envelope assemblies complying with Sections C402.2 and C402.4.4.
EXCEPTION: | Low energy greenhouses that comply with Section C402.1.1.1. |
2. Interior partition building thermal envelope assemblies that separate the greenhouse from conditioned space complying with Sections C402.2, C402.4.3 and C402.4.4.
3. Fenestration assemblies complying with the thermal envelope requirements in Table C402.1.1.3. The U-factor for the skylight shall be for the roof assembly or a roof that includes the assembly and an internal curtain system.
EXCEPTION: | Unheated greenhouses. |
4. No mechanical cooling is provided.
5. For heated greenhouses, heating is provided by a radiant heating system, a condensing natural gas-fired or condensing propane-fired heating system, or a heat pump with cooling capacity permanently disabled as preapproved by the jurisdiction.
Table C402.1.1.3
Fenestration Thermal Envelope Maximum Requirements
Component | U-Factor BTU/h-ft2-°F |
Skylights | 0.5 |
Vertical fenestration | 0.6 |
[Statutory Authority: RCW
19.27A.045 and chapter
19.27A RCW. WSR 24-16-145, § 51-11C-40211, filed 8/7/24, effective 9/7/24. Statutory Authority: RCW
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19.27 RCW. WSR 22-14-091, 23-12-101, and 23-20-021, § 51-11C-40211, filed 7/1/22, 6/7/23, and 9/25/23, effective 3/15/24. Statutory Authority: RCW
19.27A.025,
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19.27 RCW. WSR 20-21-080, § 51-11C-40211, filed 10/19/20, effective 2/1/21. Statutory Authority: RCW
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19.27 RCW. WSR 19-24-040, § 51-11C-40211, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW
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19.27A.045,
19.27A.160, and
19.27.074. WSR 16-24-070, § 51-11C-40211, filed 12/6/16, effective 5/1/17. Statutory Authority: RCW
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19.27.074. WSR 16-03-072, § 51-11C-40211, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW
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19.27 and
34.05 RCW. WSR 13-04-056, § 51-11C-40211, filed 2/1/13, effective 7/1/13.]