The IECC is actually not a code, but instead a template for legal jurisdictions to use to implement an energy code. These jurisdictions may adopt the IECC in whole, in part or modify it based on local needs.
Today, most states have energy codes based on IECC and the ASHRAE/IES 90.1 energy standard. IECC references ASHRAE/IES 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, currently the national energy standard, as an alternative standard.
The IECC lists requirements and minimum standards for the design of lighting and other energy-using systems and features of energy-efficient buildings. This article by the Lighting Controls Association describes the basic requirements of the IECC, highlighting major lighting-related changes in the new 2012 version. Note that for each feature described, exceptions may apply; consult IECC 2012 for specific details.
Residential and commercial requirements in the 2012 IECC are more strongly differentiated in two separate sections.
The residential lighting provisions in the 2012 IECC are relatively simple. Mainly, at least 75% of the lamps in permanent light fixtures must be high-efficacy, defined as T8 or smaller-diameter linear fluorescent lamps, or lamps with a minimum efficacy of 40 lumens/W for <15W, 50 lumens/W for 16-40W, and 60 lumens/W for >40W lamps. In the 2009 IECC, 50% of the lamps were required to be high efficacy.
The commercial section of 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 by building and space type, with the designer and owner ultimately deciding how best to accomplish the lighting goals within the power constraint.
Occupancy sensors. Occupancy sensors are now specifically required in a series of spaces, including classrooms, conference/meeting rooms, employee lunch and break rooms, private offices, restrooms, storage rooms, custodial closets, and other enclosed spaces 300 sq.ft. or smaller. The sensor must turn the lights OFF within 30 minutes of vacancy and provide manual-ON or auto-ON-to-<50% operation.
Daylight harvesting. The 2012 IECC follows the 2009 IECC in requiring general lighting in defined daylight zones (areas expected to receive high, consistent daylight levels) to be separately controlled from other general lighting in the space.
While daylight zones define an area of daylight availability and separate control, the system designer then determines on their own how best to zone the lighting for manual or automatic control. IECC 2012 limits the maximum size of these control zones to 2,500 sq.ft. Options for automatic daylight harvesting control include continuous dimming with a 100% to <35% light output range or multilevel controls offering 100%, a step between 50% and 70%, and another step between OFF and 35%.
Additional controls. The 2012 IECC further requires 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.
Interior lighting power allowances. The interior lighting power allowances, expressed as W/sq.ft., or lighting power density (LPD), are largely unchanged from the 2009 IECC, with these exceptions:
* 1.0 to 0.9W/sq.ft. for office;
* 1.5 to 1.4W/sq.ft. for retail;
* 0.8 to 0.6W/sq.ft. for warehouse buildings;
* 0.8W/sq.ft. for fire stations, new to the list; and
* reduction from a base of 1000W to 500W for the additional retail lighting power allowance.
With the 2012 version, 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 IECC Space by Space Method is based on ASHRAE/IES 90.1, but with slight differences in the space types, and with different lighting power allowances for many spaces.
(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 tradeoffs permitted between spaces.)
Additional energy efficiency measures. Another major change in the IECC is Section C406, Additional Efficiency Package Options, which requires the building to either:
1) optimize HVAC efficiency beyond code;
2) optimize lighting efficiency beyond code; or
3) produce renewable energy onsite.
In this case of lighting, this entails achieving a lower LPD value using the Building Area Method—e.g., 0.99 instead of 1.2W/sq.ft. for school/university buildings, for example.
Readers may obtain a copy of the new 2012 IECC here.