In a New Light

The International Energy Conservation Code (IECC) is a model residential and commercial building energy code produced by the International Code Council, an organization dedicated to building safety and fire prevention. The IECC provides a list of requirements and minimum standards regulating building design, including lighting and other energy-using systems. As a model code, it is intended as a template and has no regulatory effect until a legal jurisdiction adopts it in whole or as modified.

The IECC references ASHRAE/IES 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, currently the national energy standard, as an alternative. Today, most states have a commercial building energy code in place based on IECC and ASHRAE/IES 90.1 and at least as stringent as ASHRAE/IES 90.1 2004.

First published in 1998, the IECC was updated in 2000, 2003, 2006, 2009 and 2012. The latest version more strongly differentiates residential and commercial requirements in two separate sections. In terms of lighting, the residential provisions are relatively simple. The main requirement is that at least 75 percent of the lamps in permanent lighting fixtures must be high-efficacy, which the code defines as T8 or smaller diameter linear fluorescent lamps or lamps with a minimum efficacy of 40 lumens per watt (LPW) for <15W, 50 LPW for 16–40W, and 60 LPW for >40W lamps.

On the commercial side, the code contains both mandatory and prescriptive lighting provisions. The mandatory provisions require tandem wiring in certain fluorescent applications; maximum wattage for exit signs; circuiting for daylight harvesting control; and automatic shutoff, light level reduction and other controls. The prescriptive provisions establish limits on lighting power, and the designer and owner ultimately decide how best to accomplish the lighting goals within the power constraint.

New provisions
Many lighting-related provisions are new in IECC 2012. Note that for each new feature, exceptions may apply; consult IECC 2012 for specific details.

Occupancy sensors are now specifically required in a series of spaces, including conference/meeting rooms, classrooms, lunch/break rooms, private offices, restrooms, storage rooms, custodial closets, and other enclosed spaces 300 square feet or smaller. The occupancy sensor must turn the lights off within 30 minutes of vacancy and feature manual-on or auto-on-to-<50-percent operation.

As in IECC 2009, general lighting in defined daylight zones, or areas of daylight availability suitable for daylight harvesting control, must be separately controlled from general lighting in the rest of the space. Control zones, or groups of lighting fixtures assigned to specific controllers, are defined within these daylight zones. IECC 2012 limits the maximum size of a daylight harvesting control zone to 2,500 square feet. The design may then control these zones using either manual controls or automatic daylight harvesting controls, including continuous dimming with a 100 to <35 percent light output range or multilevel controls offering 100 percent, a step between 50 and 70 percent, and another step between off and 35 percent.

Additionally, IECC 2012 contains a new list of other controls, such as separate control of display and accent lighting from general lighting, supplemental task lighting and others, bringing it more in line with ASHRAE/IES 90.1. Previous exterior lighting control requirements are continued from IECC 2009 without change.

The interior lighting power density (LPD) caps changed little from IECC 2009: 1.0 to 0.9W per square foot for office, 1.5 to 1.4W per square foot for retail, and 0.8 to 0.6W per square foot for warehouse buildings, in addition to adding fire stations (0.8W per square foot) to the list. The additional lighting power allowance for retail is reduced from a base of 1,000W to 500W. One big change is, for the first time, the IECC recognizes the space-by-space method in addition to the building area method (and total building performance method, requiring building modeling) as a compliance path, providing greater design flexibility.

The building area method specifically requires adding up the installed interior lighting power in an entire building (or major section) and ensuring it is not greater than the single interior lighting power allowance for that building type. The space-by-space method also compares the total installed lighting wattage in the building but allows the user to develop the lighting power allowance based on the space type, with each type having its own LPD and with trade-offs permitted between spaces.

The IECC space-by-space method is based on ASHRAE/IES 90.1 but with slight differences in the space types and with different LPD caps for many spaces.

A final big change is Section C406, Additional Efficiency Package Options, which requires the building to optimize heating, ventilating and air conditioning efficiency beyond code; optimize lighting efficiency beyond code; or produce renewable energy on-site. In the case of lighting, meeting the change entails achieving a lower LPD value using the building-area method—e.g., 0.99 instead of 1.2W per square foot for school/university buildings.

The result is an aggressive series of standards and requirements that provides a template for designing energy-efficient buildings. Get it at

DILOUIE, L.C., a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at

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