C405.2.5
Daylight
responsive controls.
Daylight responsive controls
complying with Section C405.2.5.1 shall be provided to control the
general lighting within
daylight zones in the
following spaces:
1. Spaces with a total of
more than 75 watts of general lighting within primary
sidelit daylight zones complying with Section C405.2.5.2.
2. Spaces with a total of more than 150 watts
of general lighting within the combined
primary and secondary daylight zones
complying with Section C405.2.5.2.
3. Spaces with a total of more than 75 watts
of
general lighting within
toplit daylight
zones complying with Section C405.2.5.3.
EXCEPTION:
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Daylight responsive controls are not
required for the following:
1. Spaces in health care facilities where patient care
is directly provided.
2. Sidelit daylight zones on the first floor above
grade in Group A-2 and Group M occupancies where the fenestration adjoins a
sidewalk
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C405.2.5.1
Daylight responsive controls
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 primary sidelit
daylight zones shall be controlled independently of lights in secondary sidelit
daylight zones in accordance with Section C405.2.5.2.
2. Lights in toplit daylight zones in
accordance with Section C405.2.5.3 shall be controlled independently of lights
in sidelit daylight zones in accordance with Section C405.2.5.2.
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 in that zone.
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 C405.2.5.2 facing different cardinal orientations
(i.e., within 45 degrees of due north, east, south, west) shall be controlled
independently of each other.
EXCEPTION:
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Up to 75 watts of general lighting are
permitted to be controlled together with lighting in a daylight zone facing a
different cardinal orientation.
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9.
Incorporate time-delay circuits to prevent cycling of light level changes of
less than three minutes.
10. The
maximum area a single daylight responsive control device
serves shall not exceed 2,500 square feet (232
m2).
11.
Occupant override capability of daylight dimming controls is not permitted,
other than a reduction of light output from the level established by the
daylighting controls.
C405.2.5.2
Sidelit daylight zone.
The sidelit daylight zone is the floor area adjacent to vertical
fenestration which complies with the following:
1. Where the fenestration is
located in a wall, the primary side-lit 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 C405.2.5.2(1).
2. The secondary sidelit daylight zone is
directly adjacent to the primary 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 2 feet, whichever is less, as indicated
in Figure C405.2.5.2(1).
3. Where
clerestory fenestration is located in a wall, the side-lit
daylight zone includes a lateral area twice the depth of the clerestory
fenestration height, projected upon the floor at a 45 degree angle
from the center of the clerestory fenestration. The
longitudinal width of the sidelit daylight zone is calculated the same as for
fen-estration located in a wall. Where the 45 degree angle is
interrupted by an obstruction greater than 0.7 times the ceiling height, the
side-lit daylight zone shall remain the same lateral area but be located
between the clerestory and the obstruction, as indicated in Figure
C405.2.5.2(2).
4. Where the
fenestration is located in a rooftop monitor, the 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 fenestra-tion 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
C405.2.5.2(3) and C405.2.5.2(4).
5.
If the rough opening area of a vertical fenestration assembly is less than 10
percent of the calculated primary sidelit daylight zone area for this
fenestration, it does not qualify as a sidelit daylight zone.
6. The visible transmittance of the
fenestration is no less than 0.20.
7. The projection factor (determined in
accordance with Equation 4-5) for any overhanging projection which 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 C405.2.5.2(1) Sidelit Daylight Zone Adjacent to
Fenestration in a Wall
Click to view
image
Figure C405.2.5.2(2) Sidelit Daylight Zone Adjacent to
Clerestory Fenestration in a Wall
Click to view
image
Figure C405.2.5.2(3) Sidelit Daylight Zone Under a Sloped
Rooftop Monitor
Click to view
image
C405.2.5.3
Toplit daylight zone.
The toplit daylight zone is the floor area underneath a roof fenestration
assembly which complies with 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 C405.2.5.3(1).
2. Where toplit daylight zones overlap with
sidelit daylight zones, lights within the overlapping area shall be assigned to
the toplit daylight zone.
3. The
product of the visible transmittance of the roof
fenestra-tion assembly and the area of the rough opening of
the roof fenestra-tion assembly, divided by the area of the toplit daylight
zone is no less than 0.008.
4.
Where located under atrium fenestration, the toplit daylight zone shall include
the bottom floor area directly beneath the atrium fenestration, and the top
floor directly under the atrium fenestration, as indicated in Figure
C405.2.5.3(4). The toplit daylight zone area at the top floor is calculated the
same as for a toplit daylight zone. Intermediate levels below the top floor
that are not directly beneath the atrium are not included.
Figure C405.2.5.3(1) Toplit Daylight Zone Under a Rooftop
Fenestration Assembly
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image
Figure C405.2.5.3(2) Toplit Daylight Zone Under a Rooftop
Monitor
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image
Figure C405.2.5.4 Toplit Daylight Zone Under Atrium
Fenestration
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image
C405.2.5.4
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 C405.2.5.4.