Outdoor Lighting Guide

This is a Guide to making outdoor lighting choices that will help preserve Nantucket’s starry nights as well as the nighttime environment that is so important to our quality of life, the island’s historic charm, and its wildlife – in short, a roadmap for lighting the outdoors with the Nantucket we all love in mind.

It provides practical guidance for complying with Nantucket's outdoor lighting bylaw (as amended at Nantucket’s 2023 Annual Town Meeting), as well as for going beyond the minimum requirements of the bylaw to be as dark-sky and neighbor friendly as possible.

Be a star. With the help of this Guide, please do your part to preserve an important part of Nantucket’s heritage and culture.

Introduction

What's at Stake

Nothing can beat the magic of the Nantucket sky on a clear night. Thirty miles at sea, the island can feel at times like an ocean liner, alone beneath a canopy of stars. It’s a view to stir the soul and one that has been cherished for centuries by residents and visitors. But that velvety blackness, and the celestial bodies it reveals, could be lost to us if we’re not careful.

Satellite data shows that our night skies are 25% brighter than they were just ten years ago, and it's likely even worse than that because satellites are essentially blind to the blue light emitted by LEDs. The culprit is light pollution – a catchall term for the negative effects of poorly designed or excessive artificial light at night – and if we don't do something about it, future generations may no longer be able to see the Milky Way, shooting stars, and the constellations.

And it's not just our view of the stars thats at stake. Light pollution is:

a serious quality-of-life issue for many, interfering with their sleep and enjoyment of their own property;
eroding the island’s historic character;
harmful to birds, pollinating insects, plants, and other wildlife;
compromising our safety and security;
a waste of energy; and
potentially harmful to human health.

To learn more, click here.

Help Nantucket become an International Dark Sky Community

For Nantucket to achieve certification as an International Dark Sky Community — a coveted designation awarded to communities that show an exceptional dedication to preserving the night sky — we must demonstrate (among other things) the use of dark sky friendly outdoor lighting by a significant number of businesses and homeowners as well as by the Town of Nantucket. Please do your part to help by ensuring that your own outdoor lighting is dark sky friendly!

Click here to learn more.

Outdoor Lighting Fundamentals

An understanding of the topics covered here is important for complying with Nantucket's outdoor lighting bylaw, particularly its requirements related to color temperature and lumens. If you're already familiar with these fundamentals, feel free to skip ahead.

Principles for Responsible Outdoor Lighting

The principles for responsible outdoor lighting jointly adopted in 2020 by DarkSky International and the Illuminating Engineering Society underlie the outdoor lighting bylaw adopted at Nantucket's 2023 Annual Town Meeting. Where you can be even more dark-sky friendly than the bylaw requires by following these principles, we encourage you to do that!

Use light only if it is needed. All light should have a clear purpose. Consider how the use of light will impact the area, including wildlife and their habitats.
Direct light so it falls only where it is needed. Use shielding and careful aiming to target the direction of the light beam so that it points downward and does not spill beyond where it is needed.
Light should be no brighter than necessary. Use the lowest light level required. Be mindful of surface conditions, as some surfaces may reflect more light into the night sky than was intended.
Use light only when it is needed. Use controls such as timers or motion detectors to ensure that light is available when it is needed, dimmed when possible, and turned off when not needed.
Use warmer color lights where possible. Limit the amount of shorter wavelength (blue-violet) light to the least amount needed.

SOURCE:

https://darksky.org/resources/guides-and-how-tos/lighting-principles/.

"Fully Shielded" Fixtures

Stated simply, fully shielded fixtures are designed and installed so that no light is emitted upwards, either directly or indirectly. This is the gold standard for preserving starry nights and avoiding light trespass and glare.

A few things to keep in mind:

Even if a fixture is designed to be fully shielded, if a longer bulb is used than what's intended and it extends below the fixture, that renders the fixture NOT fully shielded. Be sure to use the correct bulb.
Fixtures that have side panels made of glass or another material that is fully or semi transparent are NOT fully shielded (despite any claims to the contrary by the manufacturer) because the side panels reflect some of the light upwards.
All fixtures formally approved by DarkSky International (formerly known as the International Dark Sky Association) are fully shielded. However, "DarkSky Approved" LED fixtures that don't have a changeable bulb may not satisfy the color temperature and lumen restrictions of the outdoor lighting bylaw even though they are fully shielded. This may also be true of other fixtures marketed as "dark sky" fixtures.

More examples of fully shielded fixtures are provided here.

Think Lumens, not Watts

For years we’ve bought light fixtures and bulbs based on wattage – the amount of energy used – and associated that with their brightness. But with the introduction of more energy-efficient alternatives to incandescent bulbs, wattage is no longer an accurate way to gauge brightness. A 9-watt LED may be as bright as a 60-watt incandescent bulb. So, today, the best way to judge the brightness of a fixture or bulb is based on its lumen output, which is a direct measurement of the amount of light that the fixture or bulb emits. The higher the lumen value, the brighter the light.

What is the lumen output of standard incandescent bulbs?

For those still used to gauging brightness based on the wattage of incandescent bulbs, here are the commonly accepted lumen values for standard incandescent bulb wattages (in reality, this varies from manufacturer to manufacturer depending on the energy efficiency of their bulbs).

40W = 450 lumens

60W = 800 lumens

75W = 1100 lumens

100W = 1600 lumens

150W = 2600 lumens

Learn more about lighting and lumens here: https://www.energy.gov/energysaver/lumens-and-lighting-facts-label

How many lumens are needed for outdoor lighting?

The amount of lumens needed for outdoor lighting depends on what it’s being used for.

For example, 200 to 500 lumens is considered adequate for lighting an entryway. If you are using multiple fixtures, 250 lumens per fixture should be enough. If you have large windows that let indoor light outside, you may need even fewer lumens.

For other types of outdoor lighting, here's what is generally recommended.

Step lights: 12-100 lumens
Hardscape lights (on walls): 50-185 lumens
Landscape lights: 50-300 lumens
Landscape spotlights: 120 lumens
Path lights: 100-200 lumens
Lamp posts: 120-180 lumens
Pool lights: 200-400 lumens
Motion sensor lights: 300-700 lumens
Flood lights: 700-1300 lumens

Following these recommendations will help you stay within the lumens allowed under the outdoor lighting bylaw.

SOURCE:

https://www.homedepot.com/c/ab/how-many-lumens-needed-for-outdoor-lighting/9ba683603be9fa5395fab90170e343cd

https://www.lightingforgardens.com/blog/how-many-lumens-do-you-need-for-outdoor-lighting

https://nvlightingga.com/blog/how-bright-should-outdoor-lighting-be

https://www.streetlights-solar.com/how-many-lumens-do-i-need-for-outdoor-lighting.html

What is color temperature and why is it important?

Correlated color temperature (CCT) — often referred to as just "color temperature" — is a way of describing the hue or tint of light, ranging from warm (amber) to cool (bluish), and is measured in units called Kelvin (K). The higher the Kelvin, the bluer the light and the more harmful the light is.

Blue-rich light causes the most glare and sky glow, makes it harder to see (especially for older eyes), has damaging ecological impacts, and is disruptive to circadian rhythms. (Learn more here: https://darksky.org/news/why-is-blue-light-at-night-bad.)

Because of all this potential harm, the outdoor lighting bylaw generally restricts outdoor lighting to 2700K or less, consistent with the recommendation of the Massachusetts Medical Society. Only if 2700K is not commercially available for the use in question (rare, these days) may a higher color temperature be used and in no case should it be higher than 3000K. (To be the most dark-sky and neighbor friendly, we recommend using 2400K or less whenever possible.)

On some packaging, color temperature is referred to as Light Appearance.

Beware of terms like "warm white," "soft white," and "cool white" to describe color temperature (or Light Appearance) in lieu of a Kelvin (K) value. Manufacturers use these terms differently. For example, some use "warm white" to describe 3000K or less and others use it to describe 2700K or less. If the Kelvin (K) value isn't provided, contact the manufacturer for this information or choose another product.

Making sense of a light bulb "Lighting Facts" label

The Federal Trade Commission requires light bulb packaging to have a "Lighting Facts" label to provide shoppers with all the information they need to buy a bulb to meet their needs. This can be a bit confusing so here's a guide to help you understand the terms used. For preservation of dark skies, it's the lumen output and color temperature that matters. (Those terms are discussed in more detail above.)

Outdoor lighting, crime, and safety

Outdoor lighting is often intended to enhance safety and security at night, but excessive or poorly designed lighting can actually have the opposite effect.

Visibility should always be the goal. Glare from bright, unshielded lights actually decreases safety because it can be temporarily blinding as well as make it more difficult for our eyes to adjust to low-light conditions. These are potential hazards for everyone on our roads and even on your own property.

As for deterring crime, there's no conclusive evidence that bright lights do that (learn more here) and, in fact, poorly designed or installed lights can decrease security by creating blinding glare or dark shadows where those with bad intentions can hide.

In the top photo, the person at the gate isn't visible because of the glare from the bright, unshielded light. Only when the glare is removed does that person become visible.

Bottom line: following the principles for responsible outdoor lighting that are incorporated into Nantucket's outdoor lighting bylaw is the best way to have a safe and secure environment.

Keep indoor lighting indoors

Indoor lighting can contribute to light pollution when window coverings aren't used to keep the light inside. While that is beyond the scope of the outdoor lighting bylaw, we urge you to keep indoor lights indoors as much as possible!

Outdoor Lighting Bylaw

Chapter 102, Town of Nantucket Code (as amended May 2023)

Preface

We've done our best to accurately summarize the requirements of this bylaw. Of course, the language of the bylaw controls, not our interpretation of it, so please consult the bylaw itself if questions arise.

Quick Reference: Read This First. Easy Ways to Comply.

Here are easy ways to comply with the bylaw without delving into the details:

Use only bulbs and LED fixtures that are 2700K or less in color temperature (ideally, 2400K or less).
Use low-lumen bulbs, 600 lumens or less for outdoor light fixtures that aren't fully shielded and no more than 1500 lumens for fixtures that are fully shielded.
Add shields to floodlights that aren't fully shielded (and point them down) if the lumen output is more than 600 lumens and you can't or don't want to use lower lumen bulbs.
If your fixture is near another house or a publicly travelled road, replace fixtures that aren't fully shielded (e.g., onion and lantern fixtures) with ones that are, to minimize light trespass and glare and thus reduce the possibility of being charged with creating a public safety hazard or lighting nuisance.
Turn off all outdoor lights by 11pm (or, in the case of nonresidential properties, within an hour of closing).
Disable or stop using any lights that aren't needed for safety and security.
Don't use uplighting.

If you're willing to do all of the above, you are a dark-sky hero and have met or, in some cases, exceeded the minimum requirements of the bylaw.

If you aren't able or don't want to do all of the above, keep reading to see how the bylaw applies to you.

Applicability and Effective Date

New lighting installations. All outdoor lighting installed after Jan. 1, 2024, must comply with these regulations. (Sections 102-2C and 102-10)

Nonconforming existing lighting: Outdoor lighting that was installed on or before Jan. 1, 2024, that does not conform with the regulations can be used until Jan. 1, 2029, with three exceptions:

Public safety hazard or lighting nuisance. Lighting found to be a public safety hazard or nuisance under Section 102-6A must be brought into compliance within 90 days of being notified by the Town.
Substantial renovation. When more than 50% of the total assessed value or square footage of a structure is repaired or renovated, all outdoor lighting must be brought into compliance as part of the renovation.
Retrofit by the Town. If the Town of Nantucket retrofits a fixture that it owns (e.g., to convert it to LED), the fixture must be brought into compliance at the time that work is done.

(Section 102-2D(1))

Request for extension: Private property owners may request an extension from the Town Manager to use and maintain a nonconforming fixture for up to 10 years from the date the fixture was installed, provided that the fixture was compliant with the requirements that existed at the time of installation, it cost $100 or more, and it can't be brought into compliance by changing the bulb/lighting element or installing shielding (Section 102-2D(2)).

Administrative Waivers

An administrative waiver may be granted by the Town’s Lighting Enforcement Officer if a property owner demonstrates that compliance with one or more requirements would constitute an unreasonable hardship or be detrimental to health, safety, or welfare (Section 102-8).

If the unreasonable hardship is the cost of compliance, please contact Nantucket Lights about the possibility of obtaining financial assistance.

General Requirements

Outdoor lighting must comply with the following four requirements unless it falls within an exception or a general exemption:

It must be fully shielded if the lumen output is more than 600 lumens (click here for examples of fully shielded fixtures).
The color temperature must be 2700K or less.
It must not exceed specified limits on brightness (as measured in lumens).
It must be turned off during certain hours — between 11pm and 6am for residential properties, and between one hour after closing until one hour prior to opening for nonresidential properties.

(Section 102-4)

Each of these general requirements is discussed in detail here.

See below for general exemptions.

Requirements for Specific Types of Lighting

Exemptions

The following types of lighting are exempt from all the requirements and prohibitions of the outdoor lighting bylaw:

Lighting required by law to be installed on motor vehicles.
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.
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.
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.
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.
Lighthouse beacons owned by the United States Coast Guard.
Temporary lighting for events sponsored by the Town of Nantucket.
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.
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.
Underwater lighting of swimming pools or other water features.

(Section 102-7)

Prohibitions

Unless falling within an exemption, some types of lighting are altogether prohibited regardless of when it was installed. These include:

Uplighting of building facades or walls except for temporary holiday lighting.
Searchlights and sky beams except as required by public safety personnel.
Blinking, flashing or rotating lighting except for temporary holiday lighting.
Lighting on publicly owned property subject to a conservation restriction.
Lighting that creates a public safety hazard or nuisance in the form of light trespass or glare (see below), unless there are extenuating circumstances that justify an exception;

(Section 102-6)

Light trespass is when light shines beyond the property line. It constitutes a public nuisance if it exceeds the illuminance level at the property line specified in the bylaw unless the Lighting Enforcement Officers finds that there are extenuating circumstances related to safety and security that justify an exception. (Section 102-6A(1))

Glare is when bright light reduces visibility and causes visual discomfort or impairment. It constitutes a public safety hazard or nuisance when it could interfere with the safe movement of motor vehicles or when it interferes with the usual and reasonable use and enjoyment of property. (Section 102-6A(2))

Penalty for Noncompliance

Violations of this bylaw are subject to a fine of $100 for the first violation, $200 for the second violation, and $300 for the third violation and any subsequent violation (Section 102-9C(1)).

A fine may be imposed for each nonconforming fixture and each day that a violation continues constitutes a separate offense (Sections 102-9B(3) and 102-9C(2)).

Enforcement

Enforcement is the responsibility of the Town's Lighting Enforcement Officer (Section 102-9A). That position is currently held by Marcus Silverstein, msilverstein@nantucket-ma.gov, who is supervised by the Director of Planning, Leslie Snell, lsnell@nantucket-ma.gov.

Before reporting a suspected violation, we encourage you to contact the property owner in question and see if they would be willing to voluntarily make changes to their outdoor lighting. They may not be aware of the bylaw or the harm their lighting is causing. Often, a little education and gentle persuasion goes a long way! See the Resources section of this Guide for a suggested "Dear Neighbor" letter.

Definitions

For the purposes of this bylaw, the definitions found in Section 102-3 (repeated below) apply unless a contrary meaning is required by the context or is specifically prescribed:

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

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.

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.

ILLUMINANCE

The amount of light falling onto a given surface area, often measured in units called foot-candles.

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.

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.

UPLIGHTING

Lighting placed or designed to shine the light above the horizontal plane at the point where the light is emitted.

History

The outdoor lighting bylaw was proposed by Nantucket Lights founder Gail Walker and adopted at Nantucket's 2023 Annual Town Meeting (Citizen Warrant Article 76) on a vote of 298-152, following a motion to amend by Nantucket Public Schools Superintendent Beth Hallett that was defeated on a vote of 169-288.

Prior to the vote, the proposal received a positive recommendation from the Town’s Finance Committee and was endorsed by the Nantucket Civic League, the Nantucket Historical Commission, the Nantucket Land and Water Council, and many neighborhood associations.

Following its adoption, the bylaw was approved by the Massachusetts Attorney General on Sept. 8, 2023. See Town of Nantucket Notice here.

Resources

FAQ

Click here for answers to frequently asked questions.

Checklist

Click here for a checklist to help you determine what changes, if any, are needed to comply with the outdoor lighting bylaw.

Outdoor Lighting Inventory Form

Click here for an inventory form to help you determine what changes, if any, are needed to comply with the outdoor lighting bylaw.

Dark Sky Products

Click here for some examples of the many dark-sky friendly products that are commercially available. Note that these are subject to change as new products are discovered.

Dear Neighbor Letter

Click here to download a letter you can give to your neighbors. Feel free to modify it as you feel appropriate.

Information for Renters

Click here for suggested information to provide to renters. Feel free to modify this as you feel appropriate.

Financial Assistance

In most cases, the cost of complying with the outdoor lighting bylaw will not be expensive. However, if you need financial assistance to upgrade your lighting, we will try to help. Please complete this application form.

OUTDOOR LIGHTING GUIDE

Lighting with Nantucket in Mind

Special Offer

Introduction

Outdoor Lighting Fundamentals

Outdoor Lighting Bylaw

Resources

Acknowledgements

OUTDOOR LIGHTING GUIDE

Lighting with Nantucket in Mind

Special Offer

Introduction

Outdoor Lighting Fundamentals

Outdoor Lighting Bylaw

Resources

Acknowledgements

Cookie Notice