Increasing Efficiency by Design

By Oct. 18, 2013, all states in the United States must put in place a commercial building energy code at least as stringent as the ASHRAE/IES 90.1 2010 energy standard, according to a Department of Energy (DOE) ruling on Oct. 19, 2011.

ASHRAE/IES 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, is a model energy code produced by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Illuminating Engineering Society (IES). First published in 1975, it was updated in 1980, 1989, 1999, 2001, 2004, 2007 and 2010. It regulates building energy efficiency by imposing requirements on design.

Today, most states have adopted 90.1 or the International Code Council’s (ICC’s) International Energy Conservation Code (IECC) either verbatim or amended as their commercial building energy code. The IECC references 90.1 as an alternative compliance standard. Some states, such as California, have created their own code, and others have no code for various reasons, such as home rule constitutions requiring adoption of codes at the county level of government.

The 2004 version of 90.1 was the national energy standard until July 2011. At that time, the DOE issued a ruling recognizing the 2007 version. Regarding the lighting requirements, there is not much difference between the 2004 and 2007 versions of 90.1. In October 2011, the DOE recognized the 2010 version of 90.1, which differs significantly in the lighting department. According to, more than half of the states have already adopted codes at least as stringent as the 2007 version, which may have prompted the DOE to jump to the next level.

Also in July 2011, the DOE issued a rule requiring new federal buildings, for which construction design begins on or after Oct. 11, 2012, to comply with ASHRAE/IES 90.1 2007. The October 2011 ruling did not change that.

So what will be required? ASHRAE/IES 90.1 includes both mandatory and prescriptive lighting provisions. Mandatory provisions cover lighting controls, tandem wiring, exit signs and outdoor building grounds lighting. The prescriptive part establishes maximum allowed lighting power density (LPD, in watts per square foot) for spaces and buildings. The designer may comply with LPD on a building-area basis by building type, space-by-space-area basis by space type, or through building energy modeling.

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 total allowance is calculated as a space-weighted average.

With regard to lighting, the 2010 standard’s scope expanded from new construction and renovation to lamp-plus-ballast retrofits in which 10 percent or more of the connected lighting load is an indoor or outdoor area. For these lighting alteration projects, the owner must meet LPD limits and automatic shut-off requirements.

While LPD caps were raised for some space types, caps were lowered in a majority of building and space types, making 2010 more stringent than preceding versions. The lower the lighting-power allowance, the more expertise is required to satisfactorily serve two masters: the energy code and occupants who want a high-quality lighting environment.

The lighting control requirements are dramatically expanded in the 2010 version, requiring automatic shut-off controls covering both indoor and outdoor lighting and with all interior automatic controls restricted to manual-on or auto-on-to-50-percent operation, bilevel switching for stairwells and space control, occupancy sensors in a broad range of space types, daylight harvesting in daylighted spaces, and other requirements covering specific applications. Additionally, a list of advanced options—such as automatic continuous daylight dimming—are identified with power adjustment credits for basic space types, such as office, meeting, retail and public spaces. These factors can be applied to adjust a space’s LPD caps, rewarding adoption of these advanced control strategies with a higher design lighting power allowance. All lighting controls must be calibrated, adjusted, programmed and functionally tested to ensure options in accordance with construction documents and manufacturer installation instructions.

Finally, certain documents must be turned over to the owner at project completion, including as-built drawings, operating and maintenance manuals, recommended relamping program, a schedule for inspecting and recalibrating lighting controls, and a complete narrative of how each lighting control system is supposed to operate.

These requirements will challenge lighting designers to provide energy--efficient and well-lighted spaces, automatic shut-off control in retrofits, and a stronger role for electrical contractors able to offer functional testing and the required documentation.

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

About the Author

Craig DiLouie

Lighting Columnist
Craig DiLouie, L.C., is a journalist and educator specializing in the lighting industry. Learn more at and .​

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