The Pol 04 credit references the ILP obtrusive guidance notes which have now been updated.
The ILP Guidance notes for the Reduction of Obtrusive Light, 2020 are available free of charge from the ILP website www.theilp.org.uk.
Tables 3-8 of the ILP guidance and their accompanying notes outline four sets of recommendations:
- Limits to the average upward light ratio of the luminaires, to restrict sky glow.
- Limits to the illuminance at the windows of nearby properties for which light trespass might be an issue.
- Limits to the intensity of each light source in potentially obtrusive directions beyond the site boundaries.
- Limits to the average luminance of the building if it is floodlit.
In each case the limiting values depend on the location of the site of the building (e.g. rural, urban or city centre). A calculation of illuminance (2) or intensity (3) is not required if all luminaires are cut-off types and angled so that light in potentially obtrusive directions is blocked.
This update will be reflected in the next version of the manual.