The purpose of this chapter is to establish regulations for
outdoor lighting that:
A. Minimize the unintended and/or adverse impact of the use of artificial
light at night (commonly known as light pollution) to the greatest
extent possible, in recognition of its negative effects on people
as well as wildlife.
B. Protect residents from light trespass that negatively affects the
enjoyment of their own property and their property values.
C. Control glare to increase the safety and security of residents and
visitors.
D. Minimize skyglow to preserve the ability to see the stars and Milky
Way, thereby preserving humanity's connection with the night
sky, fostering awe and wonder in current and future generations of
children as well as adults, and preserving the ability of the Maria
Mitchell Association to conduct astronomical research.
E. Provide adequate light for the safe performance of outdoor tasks
at night and to keep property free from harm.
F. Promote efficient and cost-effective lighting to conserve energy.
G. Preserve the historic and rural character of Nantucket.
BUG RATING SYSTEM
A lighting classification system created by the Illuminating
Engineering Society (IES) and the International Dark-Sky Association
(IDA) to describe the light pollution contributions from outdoor luminaires.
"B" relates to backlight, which often contributes to light trespass.
"U" relates to uplight, which contributes to skyglow and limits the
ability to see the stars. "G" relates to glare, which makes it difficult
to see.
CORRELATED COLOR TEMPERATURE (CCT)
A specification of the color appearance of the light emitted
by a lamp, measured in units called Kelvin (K). Correlated color temperature
(CCT) values are typically provided in lighting manufacturer data
sheets.
EMERGENCY LIGHTING
Temporary lighting required for public safety in the reasonable
determination of public safety officials.
ENVIRONMENTALLY SENSITIVE AREA
Any land that contains threatened or endangered species habitats,
is used for agricultural purposes, or is subject to a conservation
restriction.
EXTERNALLY ILLUMINATED SIGN
Any sign or display whose information content is made visible
at night by means of a luminaire mounted at some distance above, below,
or otherwise away from the surface containing the information or message
intended to be seen.
FLOODLIGHT
Any luminaire or lamp that incorporates a reflector or refractor
to concentrate the light output into a directed beam in a particular
direction.
FOOTCANDLE
A measurement of illuminance equivalent to one lumen per
square foot.
FULLY SHIELDED LUMINAIRE
A luminaire that is constructed so that, in its properly
installed position, all the light emitted shines below the horizontal
plane at the point where the light is emitted. See Figure 1 (below).
Luminaires with adjustable aiming are not fully shielded unless they
are aimed and shielded so that no light is emitted above the horizontal
plane at the point where the light is emitted.
Figure 1. Fully Shielded Luminaire
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GLARE
Intense light emitted by a lamp or luminaire that reduces
visibility and creates visual discomfort and/or momentary visual impairment.
HOLIDAY LIGHTING
Temporary decorative lighting installed in connection with
a national, state, local or religious holiday.
ILLUMINANCE
The amount of light falling onto a given surface area, often
measured in units called footcandles.
ILLUMINATING ENGINEERING SOCIETY (IES)
The professional society of lighting engineers and other
lighting professionals that is recognized as an authoritative body
on the science and application of lighting and which publishes and
promotes recommended practices for a variety of specific lighting
applications.
KELVIN
A unit of measurement used for the correlated color temperature
of light. Often denoted with the symbol K.
LAMP
The component of a luminaire that is the light source, not
inclusive of any reflective or refractive optics used to direct light.
This refers to bulbs that are easily removable and replaceable as
well as integrated systems like light emitting diodes (LEDs).
LANDSCAPE LIGHTING
Any lighting used to illuminate trees, shrubs, or other plant
material, as well as water features and decorative objects, in a yard,
garden, park, or pool deck.
LIGHT POLLUTION
Any unintended and/or adverse impact of the use of artificial
light at night.
LIGHT TRESPASS
Any light emitted by a luminaire that shines beyond the property
on which the luminaire is installed and increases the illuminance
at the property boundary line.
LUMEN
A unit of measurement of the amount of light emitted by a
luminaire or lamp, typically displayed by the manufacturer as part
of the product specification. Distinct from watts, which measures
the amount of power consumed by a luminaire or lamp rather than the
amount of light emitted. When used in this chapter, "lumens" refers
to the number of lumens of light emitted by a luminaire when the lamp
is new, not accounting for any depreciation over time, known as initial
lumens.
LUMINAIRE
A complete lighting unit, consisting of one or more lamps,
housing, lenses, reflectors, and other structural elements, but not
including any mounting pole or surface. This includes what is commonly
referred to as a light fixture as well as other types of lighting
units such as string lights and rope lights.
LUMINANCE
A measure of light emitted by or from a surface. Measured
in candelas per square meter (cd/m2).
SAFETY AND SECURITY LIGHTING
Lighting that is intended to prevent accidents and/or deter
or detect intrusions or other criminal activity occurring on a property
or site. For the purposes of this chapter, this shall include lighting
for entrances, walkways, roadways, parking lots, equipment yards,
and building security, but shall not include landscape lighting, string
lighting, rope lighting, decorative and accent lighting.
SKYGLOW
A glow in the night sky deriving from an artificial source
(or sources) of light.
SPORTS LIGHTING
Lighting to illuminate outdoor fields and other surfaces
used for the practice and/or play of any outdoor sport or athletic
activity. This term refers only to lighting intended to facilitate
play on outdoor surfaces, or to illuminate spectator viewing stands,
but not for illumination of any other part of a connected or adjacent
property such as a parking area.
SPOTLIGHT
A type of luminaire designed to project a narrow, intense
beam of light on a small area.
STRING LIGHTS
A type of luminaire consisting of small white or differently
colored electric lights spaced evenly along a cable and used for decoration,
including but not limited to "bistro" lights, "fairy" lights, and
"festoon" lights.
UPLIGHTING
Lighting placed or designed to shine the light above the
horizontal plane at the point where the light is emitted.
VERTICAL ILLUMINANCE
The amount of light falling on a vertical surface or plane.
When measuring vertical illuminance, the illuminance meter is held
vertically rather than horizontally.
All luminaires not specifically exempted in §
102-7 of this chapter shall comply with the following requirements:
A. Shielding. All luminaires with a lumen output greater than 600 lumens
shall be fully shielded except as follows:
(1) String lights, provided they comply with §
102-5A of this chapter.
(2) Temporary holiday lights, provided they comply with §
102-5C of this chapter.
(3) Luminaires for the lighting of flags, provided they comply with §
102-5D of this chapter.
(4) Sports lighting on nonresidential properties, provided it complies with §
102-5F of this chapter.
B. Correlated color temperature. The correlated color temperature (CCT)
of the light emitted by luminaires shall not exceed 2,700 Kelvin,
except as follows:
(1) If a 2,700 Kelvin (or lower) luminaire is not commercially available
for the application in question, a luminaire with a CCT of up to 3,000
Kelvin may be used unless otherwise provided by this chapter.
(2) Temporary holiday lighting is exempt from this requirement, provided it complies with the requirements stated in §
102-5C of this chapter.
(3) Sports lighting on nonresidential properties is exempt from this requirement, provided it complies with the requirements stated in §
102-5F of this chapter.
C. Lumen limits.
(1) Total lumens allowed per site. On no parcel or property shall the
total lumen output of all luminaires exceed 20,000 total lumens per
acre for residential properties or 40,000 total lumens per acre for
nonresidential properties, regardless of shielding.
(a)
Temporary holiday lighting and nonresidential sports lighting
may be excluded when determining total lumens.
(b)
For lighting within or mounted on external canopies at vehicle
fueling stations and drive-through bank tellers or automated teller
machines, an additional 10 lumens per square foot of canopy area shall
be allowed.
(2) Total lumens allowed for unshielded luminaires. On no parcel or property
shall the total lumen output of the luminaires that are not fully
shielded (excluding temporary holiday lighting) exceed a value of
5,000 lumens multiplied by the number of acres, or a total of 2,000
lumens, whichever is greater. Any luminaire that is either not fully
shielded by design or is installed so that light shines above the
horizontal plane at the point where the light is emitted shall be
counted as an unshielded luminaire for the purpose of this limitation.
(3) Maximum lumen allowed for a luminaire. The lumen output of any luminaire
on a residential property shall not exceed 1,500 lumens and the lumen
output of any luminaire on a nonresidential property shall not exceed
5,000 lumens.
D. Hours of illumination.
(1) All lighting, with the exceptions listed below, shall be turned off
by 11:00 p.m. or, in the case of nonresidential properties, within
one hour of the end of normal business or operating hours. Lighting
may not be turned on earlier than 6:00 a.m. or, in the case of nonresidential
properties, earlier than one hour prior to the start of business or
operations.
(2) The following exceptions shall apply:
(a)
Safety and security lighting: On residential properties, safety and security lighting may be used throughout the night. On nonresidential properties, safety and security lighting may be used throughout the night only if any luminaire with a lumen output above 600 lumens is controlled by motion sensor or other automatic controls so that the light output is automatically turned off or dimmed by at least 50% when activity has not been detected for 15 minutes or more. This requirement does not apply to streetlights, which may be used throughout the night provided they comply with §
102-5G of this chapter.
(b)
Lighting of flags may be used throughout the night, provided it complies with the requirements of §
102-5D of this chapter.
(c)
Sports lighting on nonresidential properties shall be turned
off by 10:00 p.m. or within one hour of the end of active play, whichever
is later.
The following types of lighting shall be exempt from the requirements
and prohibitions of this chapter:
A. Lighting required by law to be installed on motor vehicles.
B. Emergency lighting, for as long as emergency conditions identified
by public safety personnel continue to exist. This includes the activities
of law enforcement, fire, and other emergency services.
C. Temporary lighting required to save life, limb, or property from
imminent peril, provided that the use of this lighting continues only
during the hours of the peril.
D. Lighting employed during repairs of roads, utilities, and similar
infrastructure, provided that such lighting is deployed, positioned,
and aimed such that the resulting glare is not directed beyond the
work area.
E. Any form of lighting whose use is mandated by any legal jurisdiction
with broader authority than that of the Town of Nantucket, provided
that the lighting does not exceed the minimum requirements of that
legal mandate.
F. Lighthouse beacons owned by the United States Coast Guard.
G. Temporary lighting for events sponsored by the Town of Nantucket.
H. Temporary lighting approved by the Select Board in conjunction with
a special event permit, such as for concerts, fairs, and festivals,
provided that the impact of the lighting is required to be mitigated
to the greatest extent possible.
I. Lighting produced by the combustion of fossil fuels (such as natural
gas and propane) so long as the light source is completely enclosed
in a suitable housing such as a lantern, firepit or fireplace.
J. Underwater lighting of swimming pools or other water features.
The official charged with enforcing this chapter shall have
the authority to grant a partial or complete waiver of the requirements
of this chapter if a property owner demonstrates that bringing the
luminaire(s) for which the waiver is sought into full compliance with
this chapter would either (i) constitute a demonstrably unreasonable
hardship on the applicant, as balanced against the potential impacts
of noncompliance, or (ii) result in conditions that are materially
detrimental to health, safety, or welfare.
The effective date of the adoption or amendment of this chapter
shall be January 1, 2024. If such adoption or amendment is subsequently
disapproved, in whole or in part, by the Attorney General, this chapter
as it would have read without the disapproved portion of the adoption
or amendment so voted, shall be deemed to have continued in effect
from the date stated above.
The provisions of this chapter are hereby declared to be severable
and, if any provision or the application of such provision to any
property, person or circumstance shall be determined to be invalid,
such invalidity shall not be construed to affect the validity of any
other provision hereof or the application of any provisions to any
other property, person, or circumstances. The invalidity of any section
or provision of this chapter shall not invalidate any other section
or provision thereof.