Establish Design Criteria

In the previous version of this course we discussed the IES lighting guidelines in terms of four documents: IES RP-20-14, Lighting for Parking Facilities, IES RP-33-14, Lighting for Exterior Environments, IES TM-15-11, the Luminaire Classification System and the Joint IDA-IES Model Lighting Ordinance. As previously noted, this was a sizable body of information which was difficult to navigate for many professionals. In 2018, the IES combined the first two of these documents along with a summary of the third and fourth into IES RP-8-18, Design and Maintenance of Roadway and Parking Facility Lighting. While no less information is presentated, it does put all you need to know into one publication!

The first task is to identify the "Lighting Zone" where our project is located. This is discussed in RP-8-18, Chapter 4: Obtrusive Light. We will assume the project is in a city business district with relatively high ambient light. This corresponds to Lighting Zone 3 (LZ3). From Table 4-2 we can identify a maximum vertical illuminance level at the property line.

 

MAXIMUM vertical illuminance at any point in the plane of the property line for LZ3: 8 lux (0.74 fc)

 

The guidelines for parking area lighting can be found in RP-8-18, Chapter 17: Parking Lots and Parking Garages. Table 17-2 provides the illuminance guidelines we are searching for. Assuming we have a smooth asphalt surface (R4) we can identify pre-curfew requirements for LZ3.

 

Target MINIMUM maintained horizontal illuminance level at grade is 5 lux (0.46 fc).

Uniformity ratio: Max/Min 15:1

 

Target MINIMUM maintained vertical illuminance level at 5’ above grade is 2.5 lux (0.23 fc).

Uniformity ratios: Max/Min 15:1

NOTE: the average to minimum ratio has been dropped in IES RP-8-18.