Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-11C - State Building Code adoption and amendment of the 2021 edition of the International Energy Conservation Code, Commercial › Section 51-11C-40232 - Section C402.4.2-Minimum skylight fenestration area

Current through Register Vol. 24-14, July 15, 2024
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 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 VTof 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
VTannual 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
spower 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 with Section C405.2.3.1.
2. The skylight effective aperture, calculated in
						  accordance with Equation 4-5, is permitted to be 0.66 percent in lieu of 1
						  percent if the VTannual of the skylight or
TDD
, as measured by NFRC 203, is greater than 38
						  percent.
C402.4.2.1
Lighting controls in
			 daylight zones under skylights.
Daylight responsive controls shall be
			 provided to control all electric lights within toplit daylight zones.
C402.4.2.2
Haze factor.
Skylights in office, storage, automotive service, manufacturing,
			 nonrefrigerated warehouse, retail store, and distribution/sorting area spaces
			 shall have a glazing material or diffuser 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 aury of skylight and light well.
C402.4.2.3
Daylight 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.