This credit seeks to reduce light pollution that can block our view of the night sky and cause human health problems as well as ecological problems for many birds, insects, and other animals. Light pollution often represents nighttime lighting that isn’t needed and that may cause light trespass and contrast, reducing visibility.

More light can be less safe

Many people think that more lighting means better nighttime safety and security. However, too much exterior lighting can make outdoor and parking areas less safe by creating high contrast between lit and unlit spaces. Among other problems, when the human eye is flooded by bright light, it becomes harder to adjust to darker areas and shadows. Too much exterior lighting also means unnecessary energy consumption. Some objectives to keep in mind when striving for safe, efficient, and aesthetically pleasing lighting design are lighting uniformity, low contrast, no glare, and preventing light from spilling off the site. This can be achieved through judicious selection of fixtures with full cutoff that direct light toward the ground but prevent it from shining up into the night sky.

Flexibility in demonstrating compliance

This credit has two compliance options, which means your team has some flexibility in how it chooses to demonstrate compliance. The credit is concerned with exterior lighting only; there are no requirements to address interior lighting under this credit.

Option 1 deals directly with your exterior fixtures (both luminaires and illuminated signage) and the lamps you use. Option 2 assesses your building’s contribution to light pollution through nighttime illumination measurements taken around the project boundary.

If some of your exterior fixtures can’t comply with Option 1, there’s still a chance that your building can comply with Option 2. Unfortunately, there’s no good way to know whether you’ll comply with Option 2 except to perform the actual measurements, so teams often try to comply with Option 1 first.

What’s New in LEED v4.1

• No changes from v4

Should I upgrade?

This credit is unchanged from v4 so shouldn’t impact your choice of rating system.