Lighting Efficiency in New Small Commercial Construction in Minnesota


This study examined the current practice in lighting system design and installation in twenty-two small commercial buildings constructed in the Twin Cities Metro Area between May, 1991, and September, 1992. At the time of construction, these buildings were subject to Minnesota Energy Code requirements equivalent to the Code of Federal Regulations (CFR) title 10, part 435.103 "1989" requirements (also equivalent to ASHRAE/IES 90.1-1989). The study looked at the number of buildings that actually complied with the "1989" and "1993" CFR requirements, and the incremental costs and savings associated with installing state-of-the-art lighting equipment.

The level of awareness of and compliance with the lighting provisions of the energy code was first investigated through discussions with design firms, design-build contractors and code officials. The design firms were aware of the code and said they design to it, but the design-build contractors were completely unaware of it. No code officials were checking compliance or enforcing the code, and they generally felt they lacked the time, budget and expertise to do so.

A random sample of new commercial construction and additions was selected from 127 possible sites in twenty-three communities, and included 10 retail, 7 office, 3 warehouse, and 2 public spaces, ranging in size from 1,400 to 79,000 square feet, with most under 50,000 square feet. Electrical plans were collected when available, and site visits were performed to inventory the lighting equipment installed in the spaces. This information was then analyzed using the DOE code compliance software package, LTGSTD 2.2, in order to determine whether the connected interior lighting power was within the limits specified by the 1989 code. The buildings were also run through the software using the more stringent 1993 numbers in order to see how much of an effect this would have had on compliance, since the 1993 values have since been incorporated into the Minnesota Code.

The efficiency of lighting equipment selected was surprisingly low, especially since 19 of the buildings are served by utilities offering DSM rebates. For example, only three of the twenty-two buildings used T8 lamps and electronic ballasts.

For the buildings surveyed, 14 passed the 1989 code while 8 failed to meet it using either the prescriptive or the system performance method. Using the 1993 numbers, only 7 would have passed, and 15 would have failed to meet the code. The buildings were then reanalyzed assuming substitution of the most efficient lamps and ballasts available without changing the layouts, to determine if compliance could be achieved by simply using more efficient equipment, or if more significant design work would be necessary to meet the code.

Simply changing from standard to high efficiency lamps and ballasts would be sufficient to enable all twenty-two sites to meet the 1989 numbers. However when these state-of-the-art systems were run through the software using the 1993 numbers, 5 sites still could not pass the code. These sites would need some further design work, or at least some controls such as energy management systems, in order to obtain credits which would allow them to pass this code.

The state-of-the-art equipment would add approximately 0.6% on average to the total cost of the buildings, but would reduce the connected lighting power by an average of 26%. With lighting accounting for over one third of the electricity cost in commercial buildings, this is a significant reduction. The paybacks for installing state-of-the-art lighting equipment at the time of construction for these sites averaged 3.2 years based on the incremental cost over the standard equipment, including utility rebates, and 3.5 years without rebates.

Clearly utilities cannot assume that code requirements are being met simply because they have been adopted, especially in small commercial buildings. Since small buildings account for 96% of commercial buildings and 56% of commercial energy use, utilities and state code officials must find more effective ways to reach this market, including better code education and enforcement, better designed and marketed incentives, and low-budget design assistance aimed at the design-build market.

Full report (PDF):
Lighting Efficiency in New Small Commercial Construction in Minnesota