ASHRAE/IESNA Standard 90.1 institutes power density limits for (W/ft2). Credits are given for using controls in the early versions, while it becomes mandatory in later versions of 90.1. This standard is used as a basis for state energy codes, and many states have adopted earlier or the most recent version. To check the status of adoption of ASHRAE/IESNA 90.1 by states into their energy codes, check

California is one of the states that has used this standard as a basis for its most recent energy-efficient regulations. CA Title 24 includes energy-efficient prescriptions for new residences, as well as requirements for day and outdoor .

Intended Outcomes:

  • Limit the power consumed by in buildings

  • Save more energy by addressing “time” portion of “energy = power X time”

  • Limit the number of incandescent sources in new residences & reduce utility load

  • Use natural light as an energy strategy, and incorporate energy efficiency into outdoor requirements

Industry Impacts:

  • More systems with higher efficacy

    W/ft2 X lm/W = lm/ft2

    Power density X Efficacy = Light Level

  • So, when power densities get smaller, efficacy must get bigger to keep light levels the same

  • Big push to produce efficient, compatible “systems,” including controls

  • Even more electronics

  • Improved luminaire optical designs

Market/User Impacts:

In CA, new residences must use some “high efficacy” in their kitchens & baths, which typically translates to the use of compact fluorescent lamps (CFL). In addition, some of the inefficient must be controlled by dimmers or occupancy sensors.

New office buildings & major retrofits all across the U.S. are now using T8 or T5 fluorescent systems – many are indirect and smaller than what they were using before. New (and retrofit) retail spaces are trying ceramic Metal Halide in lieu of halogen lamps, and industrial facilities are trying T5 High Output systems to replace standard Metal Halide.

 ASHRAE Standard
 ASHRAE/IESNA Standard 90.1-2001