Standards keep getting tighter: a lighting design that was considered very efficient a decade ago won’t earn you any points under this credit today. Even today’s standard practice is not likely to earn you points, so don’t fall in the trap of waiting until the lighting design is complete to calculate the project’s lighting power density. Instead, incorporate lighting power optimization strategies early in design to optimize lighting power density for your project and earn up to five points here. 

The best way to earn points in this credit is with a layered approach that provides relatively low-level indirect ambient light supplemented by task lighting. Direct-indirect fixtures just below the ceiling are a good solution, but the ceiling itself has to be highly reflective for that to work. That approach tends to be very cost-effective because you need fewer fixtures for indirect ambient lighting, and, if done well, it creates a very comfortable and appealing visual environment. 

Daylighting and controls don’t help with this credit

For EAp2, overall lighting power had to be reduced by 10% from ASHRAE 90.1-2007 levels. For EAc1.1, your project earns an additional point for each 5% incremental reduction you achieve, up to a total of five points for a 35% reduction (you can earn a sixth point for exemplary performance through IDc1 for 40% reduction). It helps to set reasonable goals for light levels in the space, on the lower end of IESNA standard recommendations. 

This credit addresses lighting power only—not lighting energy use. That means that good practices for reducing lighting energy use, such as occupancy sensors and daylighting with dimming controls, won’t earn you any points here, but they will with EAc1.2: Optimize Energy Performance—Lighting Controls.

Two ways to calculate

There are two ways to calculate lighting power density for your project: the building area method and the space-by-space method. The latter is more complicated, but it tends to work out better if you have a lot of display lighting or decorative lighting. The ASHRAE standard lists allowable lighting power in Section 9.5.1 for building types, and in Section 9.6.1 for individual space uses.