ASHRAE Journal - September 2023 - 48

TECHNICAL FEATURE
comply with this provision. Within North America, key
cards have significantly declined in use. The evaluation
conducted in the development of the addendum to
make this change revealed that this control method
had not yielded the intended energy savings,
explaining its declining use.
Dwelling Units
Dwellings units have different requirements for
both lighting fixtures and lighting controls from other
spaces within Standard 90.1. Standard 90.1 defines
dwelling units as a single unit providing complete
independent living facilities for one or more persons,
including permanent provisions for living, sleeping,
eating, cooking and sanitation. The luminaires and
lamps for dwelling units have an efficacy requirement.
Lighting efficacy is the " efficiency " of converting power
into visible light (lumens per watt [lm/W]). Standard
90.1-2022 Addendum br increased the efficacy for
luminaires in dwelling units to be no less than 50 lm/W
and lamps in dwelling units to be no less than 75 lm/W
for 75% of the permanently installed luminaires in the
space (Section 9.4.3).
Standard 90.1-2022 also established a requirement
for lighting controls for dwelling units. At least 50%
of the permanently installed luminaires in dwelling
units must be controlled with dimmers or devices that
automatically turn off the lighting within 20 minutes
of the space becoming unoccupied (Section 9.4.3).
Finally, Standard 90.1-2022 also established an
exterior lighting control requirement for dwelling
units. Permanently installed exterior luminaires (such
as those on a balcony or patio) dedicated to a dwelling
unit must have lighting controls that turn off the light
during daylight hours as well as when no activity has
been detected for 15 minutes in that area.
Lighting Controls
Multiple updates were made to lighting controls
requirements, including the daylighting control
wattage threshold (Section 9.4.1.1(e) and (f)); manual
dimming requirements (Section 9.4.1.1(d)); automatic
full off (Section 9.4.1.1(h)); and lighting controls in
open offices (Section 9.4.1.1(b)).
Standard 90.1-2022 reduced the wattage threshold
for daylight responsive controls to 75 W (addendum o)
for the primary sidelighted zone and 150 W for the
48
ASHRAE JOURNAL ashrae.org S E PTEM B ER 2023
secondary sidelighted zone. This change resulted from
the evaluation of updates in technology as well as the
cost and use of lighting controls. Projects determine
the area of daylighted space, and if the luminaires in
that calculated area sum to 75 W (150 W if secondary),
daylight responsive controls are required. A similar
change was made to the daylighting requirements in
toplighted spaces.
Bi-level lighting control was removed in favor of
multilevel control (addendum ba). Previous versions of
the standard required that spaces have the option of a
control point between 30% and 70% full lighting power,
which could be achieved via a dimmer, multiple switch
FIGURE 2 Open office with lights turned off, Chicago.
legs or step-ballasts. LEDs are more common and easily
dimmed, so the standard was changed to require a
manual dimmer that provides continuous dimming
from full power to 10% (or less) output.
Automatic shutoff has long been required in
Standard 90.1. Addendum ba revised the requirements
for automatic full off, adding exemptions to full off for
spaces where lighting is required for 24/7 operation
and spaces where patient care is rendered.
Open offices larger than 300 ft2 (28 m2) saw the
most significant change. Standard 90.1-2022 revised
Section 9.4.1.1(c) to address the needs of these large
open plan spaces. Previously, the standard established
9.4.1.1(c) so no more than 50% of the lighting power
could automatically turn on. This requirement also
prevented all the lights from turning on to half power.
As a result, large offices appeared dark in places
(Figure 2). To remedy this, open offices greater than
300 ft2 (28 m2) must now have occupancy controls
S E PTEM B ER 2023 ashrae.org ASHRAE JOURNAL
MICHAEL MYER
http://www.ashrae.org http://www.ashrae.org
ASHRAE Journal - September 2023

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