In 1998, the ICC released the International Energy Conservation Code (IECC), followed by a 2000 version (with 2001 supplement), 2003 version (with 2004 supplement), 2006 version (with 2007 supplement), and 2009 version. The IECC is a model energy code that covers lighting in addition to other energy-using building systems. The IECC references ASHRAE Standard 90.1 as an alternative path of compliance.
IECC 2009 contains a number of changes impacting lighting for commercial buildings, including:
• Forced choice of compliance with entirety of IECC or 90.1
• Required circuiting for independent control of lighting in “daylight zones”
• Revision of additional retail display allowances
• Added exemptions to interior lighting wattage that must be counted for compliance
• Splitting the exterior power allowance using a system of outdoor lighting zones
• Clarifications and practical application language changes
“The new IECC incorporates some useful revised language that can make compliance easier and adds some new stringency requirements that together make a generally more effective code,” says Eric Richman, LC, senior research engineer at Pacific Northwest National Laboratory and a member of the U.S. Department of Energy’s Building Energy Codes Program. “I would advise users to evaluate the option of using the alternative 90.1 Standard for compliance to get the best fit for their project. There are tools available online to help users understand the differences between the different codes and standards.”
For more information about energy codes, visit www.energycodes.gov. Also be sure to check out EE203: Lighting & Commercial Energy Codes, an LCA Education Express course.
Standard 90.1 as Alternative Compliance Path
Previous versions of IECC allowed various construction disciplines—lighting, mechanical, envelope—to be able to comply with either the applicable version of IECC or designated version of ASHRAE 90.1. IECC 2009 changed that with this section:
Section 501.2. Application. The commercial building project shall comply with the requirements in Sections 502 (Building envelope requirements, 503 (Building mechanical systems), 504 (Service water heating) and 505 (Electrical power and lighting systems) in its entirety. As an alternative the commercial building project shall comply with the requirements of ASHRAE/IESNA 90.1 in its entirety.
“This change forces all disciplines to comply with one code,” says Richman. “In the past, different disciplines have found more appropriate application for their part in one code or the other. This restriction, while easier to implement from a code official’s perspective, could limit design flexibility and overall compliance. Specifically, if the IECC path is chosen, lighting designers will not have the Space by Space Method—which is not included in IECC 2009—as an option for compliance.”
As a result, he adds, whoever designs the lighting system will need to negotiate with the project’s architect and mechanical designer to determine the best path for code compliance of the overall project, which may in some cases involve some concessions in design flexibility.
In terms of lighting controls, the primary differences between IECC 2009 and the 1999-2007 versions of ASHRAE 90.1 are the daylight zone control and light level reduction requirements in IECC 2009. But there are a number of nuances of which the designer must also be aware.
Daylight Zone Control
Since California’s Title 24-2005 energy code, energy codes have begun making attempts to realize energy savings through lighting controls that take advantage of daylighting.
IECC 2009 now addresses daylighting control, albeit gently, as only separate control zoning is required (via separate circuiting) and no specific method of control is mandated:
505.2.2.3. Daylight zone control. Daylight zones, as defined by this code, shall be provided with individual controls that control the lights independent of general area lighting. Contiguous daylight zones adjacent to vertical fenestration are allowed to be controlled by a single controlling device provided that they do not include zones facing more than two adjacent cardinal orientations (i.e., north, east, south, west). Daylight zones under skylights more than 15 ft. from the perimeter shall be controlled separately from daylight zones adjacent to vertical fenestration.
Exception: Daylight spaces enclosed by walls or ceiling height partitions and containing two or fewer light fixtures are not required to have a separate switch for general area lighting.
“This new requirement does not specify a control type, so any method, including manual switching that provides control of the daylight zone separately from the other general lighting, will comply,” says Richman.
IECC’s light level reduction (dimming or bilevel switching) requirement can be satisfied along with the daylight zone control requirement, as long as dimming or bilevel controls are provided in the daylight zone separately from other areas.
Other options include automatic shutoff and dimming based on input from a photosensor.
What spaces are affected? The code defines a “daylighting zone” differently based on whether it is adjacent to vertical fenestration (e.g., windows) or skylights:
Under skylights: The area under skylights whose horizontal dimension, in each direction, is equal to the skylight dimension in that direction plus either the floor-to-ceiling height or the dimension to a ceiling height opaque partition, or one-half the distance to adjacent skylights or vertical fenestration, whichever is least.
Daylight zone = L x W
L = the LOWEST value of …
(length of skylight) + (distance from floor to ceiling) OR
(length of skylight) + (distance to the nearest opaque ceiling-height partition such as a wall) OR
1/2 the distance between the skylight and an adjacent skylight or window
W = the same as the above, but width instead of length
Adjacent to vertical fenestration: The area adjacent to vertical fenestration which receives daylight through the fenestration. For purposes of this definition and unless more detailed analysis is provided, the daylight zone depth is assumed to extend into the space a distance of 15 ft. or to the nearest ceiling height opaque partition, whichever is less. The daylight zone width is assumed to be the width of the window plus 2 feet on each side, or the window width plus the distance to an opaque partition, or the window width plus one-half the distance to adjacent skylight or vertical fenestration, whichever is least.
Daylight zone = depth x width
Depth = the LESSER value of …
15 ft. OR
Distance from vertical fenestration and nearest ceiling-height opaque partition (e.g., wall)
Width = the LOWEST VALUE of …
Width of window plus 2 ft. on each side OR
Width of window + Distance to opaque partition (e.g., wall)
Width of window + (1/2 distance to adjacent skylight or vertical fenestration)
Exterior Lighting Control
All exterior lighting not specifically exempted by IECC 2009 must have automatic shutoff either when sufficient daylight is available or the lighting is no longer required to be operating during the night. Lighting designated for dusk-to-dawn operation therefore must be controlled by a photosensor (daylight) or astronomical time switch (scheduling).
The previous version of IECC says that non-dusk-to-dawn outdoor lighting must be controlled by an astronomical time switch. The 2009 version (Section 505.2.4) amended this to specify that non-dusk-to-dawn fixtures can be controlled by either a time switch or a combination of 1) an astronomical time switch and 2) a photosensor.
Allowing light fixtures with combined control increases flexibility by allowing the user to decide which is best for the application.
Total Interior Lighting Power—Exceptions
IECC 2009’s section 505.5.1 describes the procedure for adding up the total connected interior lighting power in a building. IECC 2009 now includes a significant number of new exceptions. One of these, in language converging with ASHRAE 90.1-2007, is included:
14. Furniture mounted supplemental task lighting that is controlled by automatic shutoff.
This change reinforces the intent that all lighting, including task lighting, should comply with the energy code as long as it’s part of the original lighting design. It also encourages automatic shutoff, which would usually be a fixture-mounted or nearby occupancy sensor.
Line-Voltage Track and Interior Lighting Power
IECC 2009 clarifies the criteria for determining the installed lighting power for line-voltage track lighting in Section 505.5.1.4.
In previous versions, the track lighting must be counted as contributing at least 30W/linear foot of track to the installed lighting power. This was to try to offset a loophole in previous codes that could not account for unlimited track heads added after installation. Unfortunately, this penalizes installations with an actual wattage below 30W.
Various manufacturers began offering devices that limit the current available for the track section to a load closer to the actual lighting design, but acceptance by code inspectors was not guaranteed. IECC 2009 has followed ASHRAE 90.1-2007 by officially recognizing these methods, stating that the input watts for line-voltage track fixtures contributing to the installed lighting power can be 30W/linear foot or the wattage limit of either 1) the system’s circuit breaker or 2) another permanent current-limiting device on the system.
“This change allows greater flexibility in design while still requiring complete accounting for all possible used wattage for compliance,” says Richman.
Solutions include sub-panels with current-limiting breakers and current-limiter track connectors with a re-settable breaker that trips if the connected load exceeds the current limit.
Additional Power Allowances for Retail Display Lighting
Following ASHRAE 90.1-2007, IECC 2009 revises additional lighting power allowances for retail spaces. IECC 2009 says that separately controlled, non-general lighting installed in sales areas and used to highlight merchandise can claim additional lighting power up to but not greater than the wattage of the specified non-general light fixtures from the applicable allowance shown in Table 1 below. These changes were made to increase application clarity and simplicity while reducing the potential for overlighting.
Interestingly, however, IECC 2009, while following 90.1-2007 in terms of its structure, has additional power allowances that are significantly lower than 90.1-2007—e.g., 0.6W/sq.ft. for Retail Sales Areas 1 and 2, which is 40% and 65% respectively lower than 90.1’s 1W/sq.ft. and 1.7W/sq.ft.; 1.4W/sq.ft. for Retail Sales Area 3, which is 46% lower than 90.1’s 2.6W/sq/ft.; and 2.5W/sq.ft. for Retail Sales Area 4, which is nearly 41% lower than 90.1’s 4.2W/sq.ft.
“The current language in IECC 2009 takes the most recent language from 90.1 applied to spaces, applies it to whole building compliance, and incorporates different lower allowances based on work done in the Northwest that looked at more efficient and somewhat higher cost technology, primarily ceramic metal halide,” says Richman. “There is still some controversy regarding the overall cost effectiveness and length of payback time in applying this technology, but the IECC chose these as part of the overall increased code efficiency strategy.”
He adds: “These new allowances may limit display design flexibility in some display-intensive retail spaces, particularly smaller areas, if cost issues are critical. However, it is unlikely that most common retail applications will adversely suffer.”
Exterior Building Lighting Power
IECC 2009 now includes a dramatically different methodology for calculating exterior building lighting power based on exterior lighting zones.
Section 505.6.2 now basically says:
Total outdoor lighting power = Base site allowance + Permitted individual allowances based on lighting zone
The base site allowances are shown in Table 505.6.2 and should be familiar to designers who have worked with the previous version of IECC.
The individual allowances are listed in Table 505.6.2(2) and are based on whether the application is in Lighting Zone 1, 2, 3 or 4.
The Lighting Zones are included in Table 505.6.2(1):
“For interior lighting, builders and specifiers are already familiar with choosing appropriate space and area types for compliance that will also be acceptable to the building official,” says Richman. “The next exterior section also requires the assignment of an appropriate exterior lighting zone. The four-zone split recognizes that exterior lighting needs for effective vision are different depending on the surrounding ambient lighting conditions. Therefore, locations with low-light surroundings do not require the same higher level of illumination as other areas.”
Typically, he says, most applications will fall into Zone 2 or Zone 3, where light level needs and therefore power allowances tend to be lower for many common applications such as parking and walkways. These allowances, however, should match the lighting needs and compliance should not be difficult if designs are based on appropriate light level recommendations.
“This one choice can affect the allowance amounts for all exterior applications and is likely to get more attention from building officials than specific area type choices,” Richman points out. “Therefore, I believe this is an area where arranging agreement on the zone choice from the building official upfront, if possibly controversial, would be a wise move to avoid potential issues later. Users should also note that the previous 5% of total exterior wattage adder has been replaced with a base allowance for the applicable exterior zone. Any user-developed calculation methods or spreadsheets need to be updated to account for this.”