ASHRAE 90.1-2013 vs. IECC 2015: Key Differences in Lighting Control

Ankit Javeri
Author : Ankit Javeri
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    With the scheduled 3-year energy code iteration in place, states have to develop and implement their own around the latest national energy reference standard, or else, justify their non-compliance with the Department of Energy, which is in charge of determining what level of codes are needed for adoption.

    ASHRAE 90.1-2013: Energy Standard for Buildings Except Low-Rise Residential Buildings, is a joint iterative process between American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Illuminating Engineering Society (IES), for the lighting part. On the other hand, International Code Council – primarily composed of building officials – developed International Energy Conservation Code or IECC 2015.

    IECC 2015 is the most widely adopted energy code in the US, but references ASHRAE 90.1-2013 as an alternative compliance path. To be clear, both ASHRAE 90.1-2013 and IECC 2015 are not codes, but provide code-ready lexicon that can be used as a basis for the state code adoption in the commercial building sector.

    Case in point, below is a summary of the lighting control requirements mandated in ASHRAE 90.1-2013 and IECC 2015 – leveraged in an apple-to-apple comparison for similarities and differences, but using the former as the baseline point for measurement.

    Interior Lighting Control

    Restricted to Manual ON

    Under Section of ASHRAE 90.1-2013, no lighting should be automatically turned on. However, this lighting control requirement is not applicable in instances where manual ON operation will compromise the safety and security of the end users. On the other hand, IECC 2015 Section C405. provides specific detail as to turning the light on manually with no more than 50% power.

    Restricted to Partial Automatic ON

    ASHRAE 90.1-2013 Section covers this lighting control by detailing that only the partial 50% of the lighting power for general lighting is allowed for automatic ON operation, while the remaining lighting power is clearly restricted from being turned on automatically.

    Likewise, IECC 2015 also poses a restriction on the partial automatic ON operation lighting power to only 50% as per Section C405. However, in public spaces such as stairways, lobbies, corridors and building entrances, full automatic-ON operation can replace the manual lighting control for the safety of the building occupants.

    Bi-Level Lighting Control

    ASHRAE 90.1-2013 Section mandates that in addition to the full ON and OFF operation of the general lighting space, the lighting should be controlled in two levels with continuous dimming or one intermediate step between 30% and 70% of full lighting power.

    IECC 2015, as per Section C405., matches this lighting control requirement by subjecting the daylight responsive controls of institutional applications — classrooms, library reading rooms, laboratories and offices — to continuous dimming of full 100% to 15% full light output.

    Automatic Daylight Responsive Controls for Sidelighting and Toplighting

    In the event that the complete or partial combined input power of general lighting on the primary sidelighted areas is 150 W or greater, the general lighting on the identified areas shall be controlled by photocontrols as per ASHRAE 90.1-2013 Section

    Using the same principle for primary and secondary sidelighted areas but with values of 300 W or higher, photocontrols shall then reduce the lighting using continuous dimming with a first control point of 50-70% design lighting power, second control point of 20-40%, and a third control point that turns off all lighting power. All values are the same for the automatic daylight responsive controls for toplighting, but the daylight areas specifically pertain to those under the skylights and roof monitors.

    In IECC 2015 Section C405.2.3.2, the lighting control states that spaces garnering more than 150 W of general lighting within sidelight or toplight daylight zones should comply with Sections C405.2.3.2 and C405.2.3.3, respectively. However, exemptions for daylight responsive controls in this code include spaces in healthcare facilities with direct patient care, dwelling units and sleeping units, and lighting with specific application control.

    Automatic Partial OFF

    ASHRAE 90.1-2013 Section describes that within 20 minutes of all building occupants evacuating the spaces, the general lighting power should be reduced in an automatic partial OFF operation by at least 50%.

    Conversely, an exception is granted when your space meets these three requirements: a lighting power density of less than or equal to 0.89 W/ft2, illuminated with high-intensity discharge (HID) light, and an automatic lighting reduction rate of 30% within 20 minutes of occupants none in sight. For IECC 2015, there’s no specific clause relating to this lighting control requirement.

    Automatic Full OFF

    Within 20 minutes of all end-users clearing the spaces, all controlled lighting should be automatically turned off as per Section of ASHRAE 90.1-2013. In as much as the same operation but with a 10-minute allowance, IECC 2015 Section C405. mandates that all lighting power in the general space should be automatically shut off within 30 minutes of being unoccupied.

    Scheduled Shutoff

    In Section of ASHRAE 90.1-2013, spaces which are scheduled for time-out can be turned off in an automatic two-way operation from a control device programmed with specific shutoff times, or security and alarm system giving signals. Note that exceptions for this lighting control requirement include spaces with 24/7 operation, constant patient care and where automatic shutoff would deem building occupants in peril.

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    Parking Garage Lighting Control

    ASHRAE 90.1-2013 Section instructs that lighting control for parking garage should have scheduled shutoff, and each luminaire should be reduced to a 30% minimum of lighting power when there are no detected activities within 20 minutes in a specific lighting zone.

    Special Applications

    Both ASHRAE 90.1-2013 and IECC 2015 have equal designations on the special lighting control applications such as display or accent lighting, guestrooms with automatic OFF operation after 20 minutes of no activity, and supplemental task lighting.

    Exterior Lighting Control

    Drafted with the same exterior lighting prerequisites, ASHRAE 90.1-2013 and IECC 2015 require curfew-based lighting with automatic OFF operation in response to sufficient daylight, and reduction to at least 30% after 15-minute inactivity or after an hour of the end of business operations.


    With energy codes updating regularly on a 3-year timeframe, lighting controls has become more stringent in performance standards. Despite this complex code compliance, buildings at par with the latest lighting codes exude sustainability – recouping you a maximum return on investment with increased energy savings. As lighting control requirements are continuously developed in the succeeding codes, our proficient electrical engineers will guide you through the exhaustive process of design, specification, and installation so your lighting project is built for success.

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    Tags : Lighting Control IECC ASHRAE

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