Interior Lighting Level Issues
October 8, 2007
NC ENERGY CONSERVATION CODE CHAPTER 805 INTERIOR LIGHTING LEVELS CHANGE UPDATE
On January 1, 2007, the NC Building Code enacted some rather startling lighting changes. The changes effect both the lighting levels as well as the controls for light fixtures. The code changes effect every type of building with the exception of dwelling units (apartments, condos, residences, and the guest rooms in a hotel). The changes that affect lighting levels can be summarized as follows:
The "Power Levels" for maximum Watts per Square Foot for all types of buildings have drastically been reduced. The most typical is for office spaces. The maximum level went from 1.5W/SF down to 1.0W/SF. This is a reduction of 33%. To illustrate this, let's take a typical office - 10' X 14' (okay, not typical, but it works well for illustration purposes because the larger size requires two light fixtures). Under the old code, you could install two 2X4 acrylics with three T8 lamps, or two 2X4 parabolics with three T8 lamps, or one 8 ft indirect fluorescent with a cross section of three T8 lamps. All three of these options gave you more than adequate footcandle levels (43, 49, and 32, respectively), but all three options use 1.27W/SF. This was way under the 1.5W/SF requirement, but it does not come anywhere close to the new 1.0W/SF requirement. Basically, it comes down to the fact that you can no longer indiscriminately use acrylic and parabolic fixtures with T8 lamps and hope to meet the energy code.
The option available to us is the newer T5 technology.
As a quick summary, here are a few of the maximum power levels now required under the North Carolina Building Code:
- Retail 1.6W/SF
- Educational 1.2W/SF
- Restaurants 1.6W/SF
- Power Levels
- New Buildings: 10.5% to 42% less than ASHRAE standards (1 to 10 points) - lighting is approximately 25% of load, so reductions below levels above help greatly
- Existing Buildings: 3.5% to 35% less than ASHRAE standards (1 to 10 points)
- We are available to lay out lights.
