The credit requirements state that the site lighting shall meet or provide lower light levels and uniformity ratios than IESNA recommendations of: (Assumed IESNA Enhanced Security Level, Zone E4, as in high personal security or high vandalism area) 1.Minimum footcandles of not less than 0.5 2.Maximum to Minimum Ratio not to exceed 15:1 3.Maximum Average not to exceed 2.5 footcandles 4.Property light spill, not to exceed 0.2 foot-candles Focus of Interpretation: Subject property has two areas of different designs: 1.Front of store parking area that has customer parking and pedestrian walkways,designed to meet IESNA Zone 4 Enhanced security level. 2.Rear and side service areas that have no customer parking or pedestrian walkways, designed to be much lower light levels as this area is service drives only, designed to meet IESNA Zone 1 Basic security level. Question: Can different IESNA requirements be applied to different parts of the site depending on use? Rational: If all calculation points within the property are calculated, the minimum footcandles would be between 0.0 and 0.2 footcandles. This would be below IESNA Enhanced Security Level recomendations of 0.5 minimum footcandles. Thus the design has been calculated in multiple statistical areas of calculations, which are as recommended by IESNA. Thank You for your consideration.
The LEED-NC Reference Guide states on page 69 that ".it is important to try to use the lowest recommended values..", and on page 72 it states "use the minimum amount of light necessary and only light areas that require it." The intent of this credit is to find ways to minimize the amount of exterior lighting without compromising security and safety. The proposed approach to have lower light levels for the back and sides of the store while providing higher levels in the customer parking lot in the front of the store is a reasonable approach consistent with the credit requirements. For submission purposes, it will be necessary however to clearly indicate the different IESNA zones on the photometric site plan and to provide separate illuminance calculations that will demonstrate compliance for each zone. Applicable internationally.