Title 16 - Buildings and Construction
16.370 ENGERGY CONSERVATION CODE
16.370.C405.2.4
Section C405.2.4 of the International Energy Conservation Code is hereby amended to read as follows; provided however, Figures C405.2.4.2(1), C405.2.4.2(2), C405.2.4.2(3), C405.2.4.3 and C405.2.4.4 shall continue to read as originally published in the 2024 International Energy Conservation Code and accordingly said figures are not reprinted but are incorporated by reference:
C405.2.4 Daylight responsive controls. Daylight responsive controls complying with Section C405.2.4.1 shall be provided to control the general lighting within daylight zones in the following spaces:
1.
Spaces with a total of more than 150 watts of general lighting within primary sidelit daylight zones complying with Section C405.2.4.2.
2.
Spaces with a total of more than 300 watts of general lighting within sidelit daylight zones complying with Section C405.2.4.2.
3.
Spaces with a total of more than 150 watts of general lighting within toplit daylight zones complying with Section C405.2.4.3.
Exceptions:
1.
Daylight responsive controls are not required for the following:
2.
Spaces in health care facilities where patient care is directly provided.
3.
Sidelit daylight zones on the first floor above grade in Group A-2 and Group M occupancies.
4.
Enclosed office spaces less than 250 square feet (23.2 m2).
C405.2.4.1 Daylight responsive control function. Where required, daylight responsive controls shall be provided within each space for control of lights in that space and shall comply with all of the following:
1.
Lights in toplit daylight zones in accordance with Section C405.2.4.3 shall be controlled independently of lights in sidelit daylight zones in accordance with Section C405.2.4.2.
2.
Lights in the primary sidelit daylight zone shall be controlled independently of lights in the secondary sidelit daylight zone.
3.
Daylight responsive controls within each space shall be configured so that they can be calibrated from within that space by authorized personnel.
4.
Calibration mechanisms shall be in a location with ready access.
5.
Daylight responsive controls shall dim lights continuously from full light output to 15 percent of full light output or lower.
6.
Daylight responsive controls shall be configured to completely shut off all controlled lights.
7.
When occupant sensor controls have reduced the lighting power to an unoccupied setpoint in accordance with Sections C405.2.1.2 through C405.2.1.4, daylight responsive controls shall continue to adjust electric light levels in response to available daylight, but shall be configured to not increase the lighting power above the specified unoccupied setpoint.
8.
Lights in sidelit daylight zones in accordance with Section C405.2.4.2 facing different cardinal orientations [within 45 degrees (0.79 rad) of due north, east, south, west] shall be controlled independently of each other.
Exceptions:
1.
Within each space, up to 150 watts of lighting within the primary sidelit daylight zone is permitted to be controlled together with lighting in a primary sidelit daylight zone facing a different cardinal orientation.
2.
Within each space, up to 150 watts of lighting within the secondary sidelit daylight zone is permitted to be controlled together with lighting in a secondary sidelit daylight zone facing a different cardinal orientation.
C405.2.4.2 Sidelit daylight zone. The sidelit daylight zone is the floor area adjacent to vertical fenestration that complies with all of the following:
1.
Where the fenestration is located in a wall, the primary sidelit daylight zone shall extend laterally to the nearest full-height wall, or up to 1.0 times the height from the floor to the top of the fenestration, and longitudinally from the edge of the fenestration to the nearest full-height wall, or up to 0.5 times the height from the floor to the top of the fenestration, whichever is less, as indicated in Figure C405.2.4.2(1).
2.
Where the fenestration is located in a rooftop monitor, the primary sidelit daylight zone shall extend laterally to the nearest obstruction that is taller than 0.7 times the ceiling height, or up to 1.0 times the height from the floor to the bottom of the fenestration, whichever is less, and longitudinally from the edge of the fenestration to the nearest obstruction that is taller than 0.7 times the ceiling height, or up to 0.25 times the height from the floor to the bottom of the fenestration, whichever is less, as indicated in Figures C405.2.4.2(2) and C405.2.4.2(3).
3.
Where the fenestration is located in a wall, the secondary sidelit daylight zone is directly adjacent to the primary sidelit daylight zone and shall extend laterally to 2.0 times the height from the floor to the top of the fenestration or to the nearest full-height wall, whichever is less, and longitudinally from the edge of the fenestration to the nearest full-height wall, or up to 0.5 times the height from the floor to the top of the fenestration, whichever is less, as indicated in Figure C405.2.4.2(1).
4.
The area of the fenestration is not less than 24 square feet (2.23 m).
5.
The distance from the fenestration to any building or geological formation that would block access to daylight is greater than one-half of the height from the bottom of the fenestration to the top of the building or geologic formation.
6.
The visible transmittance of the fenestration is not less than 0.20.
7.
The projection factor (determined in accordance with Equation 4-4) for any overhanging projection that is shading the fenestration is not greater than 1.0 for fenestration oriented 45 degrees or less from true north and not greater than 1.5 for all other orientations.
FIGURE C405.2.4.2(1)—PRIMARY AND SECONDARY SIDELIT DAYLIGHT ZONES - see figure as originally published in the 2024 International Energy Conservation Code , which is incorporated herein by reference.
FIGURE C405.2.4.2(2)—DAYLIGHT ZONE UNDER A ROOFTOP MONITOR - see figure as originally published in the 2024 International Energy Conservation Code , which is incorporated herein by reference.
FIGURE C405.2.4.2(3)—DAYLIGHT ZONE UNDER A SLOPED ROOFTOP MONITOR - see figure as originally published in the 2024 International Energy Conservation Code , which is incorporated herein by reference.
C405.2.4.3 Toplit daylight zone. The toplit daylight zone is the floor area underneath a roof fenestration assembly that complies with all of the following:
1.
The toplit daylight zone shall extend laterally and longitudinally beyond the edge of the roof fenestration assembly to the nearest obstruction that is taller than 0.7 times the ceiling height, or up to 0.7 times the ceiling height, whichever is less, as indicated in Figure C405.2.4.3.
2.
Direct sunlight is not blocked from hitting the roof fenestration assembly at the peak solar angle on the summer solstice by buildings or geological formations.
3.
The product of the visible transmittance of the roof fenestration assembly and the area of the rough opening of the roof fenestration assembly divided by the area of the toplit zone is not less than 0.008.
FIGURE C405.2.4.3—TOPLIT DAYLIGHT ZONE - see figure as originally published in the 2024 International Energy Conservation Code , which is incorporated herein by reference.
C405.2.4.4 Atriums. Daylight zones at atrium spaces shall be established at the top floor surrounding the atrium and at the floor of the atrium space, and not on intermediate floors, as indicated in Figure C405.2.4.4.
FIGURE C405.2.4.4—DAYLIGHT ZONES AT A MULTISTORY ATRIUM - see figure as originally published in the 2024 International Energy Conservation Code , which is incorporated herein by reference.
(History: Ord. No. BC-3499, §174, 2026)
Effective on: 1/1/1901
