Reducing Light Pollution: Meeting Uplight and Light Trespass Requirements

Light pollution, caused by excessive or misdirected artificial outdoor lighting, has become a growing concern in recent years. It not only affects our ability to appreciate the beauty of the night sky, but it also has negative impacts on human health, wildlife, and the environment. As a result, many organizations and building projects are now focusing on reducing light pollution by complying with uplight and light trespass requirements. In this article, we will explore two options for meeting these requirements: the Backlight-Uplight-Glare (BUG) method (Option 1) and the Calculation method (Option 2), as well as the requirements for internally illuminated signage.

Uplight Requirements

Uplight refers to the amount of light emitted from a luminaire above the horizontal plane. Excessive uplight can contribute to skyglow, which is the brightening of the night sky over populated areas. To meet uplight requirements, projects can choose between Option 1, which uses the BUG rating method, or Option 2, which uses the calculation method.

Option 1: BUG Rating Method

The BUG rating method is based on the specific light source installed in the luminaire, as defined in the Illuminating Engineering Society (IES) TM-15-11, Addendum A. The maximum uplight ratings for luminaires are provided in Table 1, based on the lighting zone of the project property, as defined by the IES/International Dark Sky Association (IDA) Model Lighting Ordinance (MLO) User Guide.

Table 1: Maximum Uplight Ratings for Luminaires

Option 2: Calculation Method

The calculation method involves determining the percentage of total lumens emitted above horizontal. The maximum allowed percentage of total lumens emitted above horizontal, by lighting zone, is provided in Table 2.

Table 2: Maximum Percentage of Total Lumens Emitted Above Horizontal, by Lighting Zone