Wash. Admin. Code § 51-11C-40232

Current through Register Vol. 24-17, September 1, 2024

Section 51-11C-40232 - Section C402.4.2-Minimum skylight fenestration area

C402.4.2Minimum 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 than 15 feet (4572 mm) for no less than 75 percent of the ceiling area.

3. Space type is one of the following: Office, lobby, atrium, concourse, corridor, gymnasium/exercise center, convention center, automotive service, manufacturing, nonrefrigerated warehouse, retail store, distribution/sorting area, transportation, and workshop.

Skylights in these spaces are required to provide a total toplit daylight zone area not less than 50 percent of the floor area and shall provide one of the following:

1. A minimum ratio of skylight area to toplit daylight zone area under skylights of not less than 3 percent where all skylights have a VT of at least 0.40, or VT_annual of not less than 0.26, as determined in accordance with Section C303.1.3.

2. A minimum skylight effective aperture, determined in accordance with Equation 4-5, of:

2.1. Not less than 1 percent using a skylight's VT rating; or

2.2. Not less than 0.66 percent using a tubular daylight device's VT_annual rating.

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EXCEPTIONS:

1. Skylights above daylight zones of enclosed spaces are not required in:

1.1. Spaces designed as storm shelters complying with ICC 500.

1.2. Spaces where the designed general lighting power densities are less than 0.5 W/ft² (5.4 W/m²) and at least 10 percent lower than the lighting power allowance in Section C405.4.2.

1.3. Areas where it is documented that existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed area for more than 1,500 daytime hours per year between 8 a.m. and 4 p.m.

1.4. Spaces where the daylight zone under rooftop monitors is greater than 50 percent of the enclosed space floor area.

1.5. Spaces where the total floor area minus the sidelit daylight zone area is less than 2,500 square feet (232 m²), and where the lighting in the daylight zone is controlled in accordance with Section C405.2.4.1.

2. The skylight effective aperture, calculated in accordance with Equation 4-tted to be 0.66 percent in lieu of 1 percent if the VT_annual of the skylight or TDD, as measured by NFRC 203, is greater than 38 percent.

C402.4.2.1Lighting controls in daylight zones under skylights. Daylight responsive controls shall be provided to control all electric lights within toplit daylight zones.

C402.4.2.2Haze factor. Skylights in office, storage, automotive service, manufacturing, nonrefrigerated warehouse, retail store, and distribution/sorting area spaces shall have a glazing material or diffus-er with a haze factor greater than 90 percent when tested in accordance with ASTM D 1003.

EXCEPTION:

Skylights and tubular daylighting devices designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles, or the geometry of skylight and light well.

C402.4.2.3Daylight zones. Daylight zones referenced in Sections C402.4.1.1 through C402.4.2.2 shall comply with Sections C405.2.5.2 and C405.2.5.3, as applicable. Daylight zones shall include toplit daylight zones and sidelit daylight zones.

Wash. Admin. Code § 51-11C-40232

Amended by WSR 16-03-072, Filed 1/19/2016, effective 7/1/2016

Amended by WSR 16-24-070, Filed 12/6/2016, effective 5/1/2017

Amended by WSR 19-24-040, Filed 11/26/2019, effective 7/1/2020

Amended by WSR 22-14-091, Filed 7/1/2022, effective 7/1/2023

Amended by WSR 24-16-145, Filed 8/7/2024, effective 9/7/2024

Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. 13-04-056, § 51-11C-40232, filed 2/1/13, effective 7/1/13.