Calculations Obtrusive Light - Concepts

AGi32 will calculate Obtrusive Light according to methods set forth by one of three standards:

Obtrusive light may be defined simply as unwanted light. More specifically, it may include light that falls onto the property of others, sometimes called spill light or light trespass, and glare, or excessive light from luminaires that hinders vision.

AS4282 further defines Obtrusive Light: "Spill light which, because of quantitative, directional or spectral attributes in a given context, gives rise to annoyance, discomfort, distraction or a reduction in the ability to see essential information, e.g. signal lights."

The AGi32 user may place appropriate calculation points (in grids or lines) as defined by either of these standards, calculate, and then run a Compliance Test to determine whether the lighting design passes or fails, according to the standard selected. The Obtrusive Light command makes placement of the lines and/or grids of points, as well as running a Compliance Test, easy.

Definitions

The following definitions are from AS4282-2019:

Obtrusive Light: Spill light which, because of quantitative, directional or spectral attributes in a given context, gives rise to annoyance, discomfort, distraction or a reduction in the ability to see essential information, e.g., signal lights.

Spill Light (stray light): Light emitted by a lighting installation which falls outside the boundaries of the property on which the installation is sited.

Threshold Increment (TI): The measure of disability glare expressed as the percentage increase in contrast required between an object and its background for it to be seen equally well with a source of glare present. Note: Higher values of TI correspond to greater disability glare.

Upward Waste Light Ratio (UWLR): The proportion of the luminous flux emitted by the luminaire above the horizontal in the installed position. Note: UWLR also meets the LEED version 4 definition of percent uplight.

 

The following definitions are from IDA/IES MLO-2011

Glare: Lighting entering the eye directly from luminaires or indirectly from reflective surfaces that causes visual discomfort or reduced visibility.

Initial Luminaire Lumens: Calculated as the sum of the initial luminaire lumens for all luminaires.

Light Pollution: Any adverse effect of artificial light including, but not limited to, glare, light trespass, sky-glow, energy waste, compromised safety and security, and impacts on the nocturnal environment.

Lighting Zone: An overlay zoning system establishing legal limits for lighting for particular parcels, areas, or districts in a community.

Property Line: The edges of the legally defined extent of privately owned property.

Uplight: For an exterior luminaire, flux radiated in the hemisphere at or above the horizontal plane.

Vertical Illuminance: Illuminance measured or calculated in a plane perpendicular to the site boundary or property line.

 

Information on placing Obtrusive Light calculation points may be found here:

Obtrusive Light - Illuminance/Intensity

Obtrusive Light - Threshold Increment

Upward Waste Light Ratio (UWLR)

 

Information on running a Compliance Test may be found here:

Obtrusive Light - Compliance Test