Lighting and the energy codes

Engineers have many resources when designing energy-efficient lighting in nonresidential buildings. Lighting designers do not have to sacrifice quality or reduce lighting levels just to meet energy codes.
By Kenneth L. Lovorn, PE, Lovorn Engineering Associates, Pittsburgh October 26, 2015

This article is peer-reviewed.Learning Objectives:

  • List the codes and standards that outline energy-efficient lighting design, such as ASHRAE Standard 90.1 and the International Energy Conservation Code.
  • Apply lighting power density to lighting design.
  • Recall that lighting design software and lighting controls play a role in lighting design. 

Prior to the 1973 gasoline crisis in the United States, energy conservation codes didn’t exist. Today, the energy laws have virtually stopped the sale of incandescent bulbs that Thomas Edison worked so hard to develop. Offices that were routinely illuminated to 200 footcandles (fc) are now illuminated to 30 fc with task lighting to make up the difference (in accordance with the Illuminating Engineering Society, IES).

Architects, developers, and owners constantly complain that there is not enough light, whether they are talking about offices, common areas, corridors, or parking lots. Historically, offices that may have used 5 W/sq ft to 8 W/sq ft for lighting, now are allocated 1 W/sq ft. Exterior lighting is greatly restricted and dark-sky initiatives, such as the International Dark Sky Association, are normally required by most authorities having jurisdiction (AHJ); general exterior lighting on building facades is no longer permitted because it wipes out the visibility of stars in the vicinity of urban areas.

For most states and jurisdictions, interior and exterior lighting design for new or renovated facilities is controlled by either ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings (2013 edition) or the International Energy Conservation Code (IECC, 2012 edition), depending on which code is adopted by the AHJ. These codes have similar restrictions concerning maximum lighting power densities (LPD) for various facilities, but they approach the final calculations in different manners.

ASHRAE gives you a list of various types of facilities and then has subcategories within each facility type with specific restrictions on the LPD for each of the space categories. For instance, a hospital is divided into 14 different space types from corridors less than 8 ft wide to recovery areas to nurse stations. The total area of the facility must then be divided into each of these categories with specific areas for each space. The calculation then multiplies each space category by its allowable LPD to come up with a total allowable lighting power permitted for the hospital. The wattages for every lighting fixture in each of the space categories is then totaled and the fixture wattage total is compared to the maximum lighting power permitted. If the total lighting fixture wattage is less than the maximum permitted wattage, then the facility passes, but if the wattage is greater, then the facility fails. Most jurisdictions will not issue an occupancy permit to a facility that fails this calculation.

For IECC’s 2009 edition—still in use in many jurisdictions—there are a number of facility types, but the total building area is used for the total lighting power. Using the hospital example, the entire building must have an LPD of less than 1.05 W/sq ft. Calculate the total hospital area and multiply it by 1.2, which results in a total lighting power for the facility. By totaling the Watts used by every light fixture in the facility and comparing it with the calculated lighting power above, the facility passes if its total lighting power is less than the permitted lighting power.

In the 2012 edition, the IECC modified its approach to more closely match the ASHRAE methodology, which allows space-by-space lighting power calculations as well as the previously described "building area method" used in the 2012 IECC.

Other lighting codes

In addition to our concentration on ASHRAE 90.1 and IECC, there are a number of federal acts and organizations that have regulations and opinions that affect lighting. These include:

Design lighting issues

As the engineer proceeds with his lighting design, applying all of the applicable codes and standards, he also must research the best way to apply the lighting fixtures that are desired by the owner and architect. He may find that the desired fixtures will not meet these codes, no matter what lighting source used in the fixtures. There are LED fixtures that now achieve more than 102 lumens/W, but T-5 fluorescent lamps manufactured by a well-known lamp manufacturer can achieve more than 105 lumens/W. Other LED fixtures still are in the 60 to 70 lumens/W range and there will be significant lighting loss by using these less-efficient fixtures.

Also, the lighting engineer should take the lamp lumen depreciation (LLD) of the selected lighting source. With an LLD of 0.91 to 0.95 for fluorescent lamps, according to data from a large fluorescent lamp manufacturer, and 0.70 for LEDs, there will be significant lighting loss due to lumen depreciation. On the positive side, the LLD is applied over 50,000 to 60,000 hr of operation for LEDs and 35,000 to 60,000 hr for selected T5 fluorescents. By carefully selecting the fluorescent lamp, relamping of fluorescent fixtures may be on the same interval as replacement of the diode elements and drivers of the LED fixtures at a significant cost savings.

Figure 1: This chart of lumen depreciation curves for various lamp types shows that the LED light sources have a greater lumen depreciation over time. While their initial lumens/Watt approach that of fluorescent lamps, the output of the T5 fluorescent lam

Software and controls

Various organizations also have software to assist the engineer in applying some of the codes to their lighting design for a facility. The one program that is commonly accepted by the AHJ is COMcheck Other programs include the Dept. of Energy’s CALiPER program, Energy Star, and LED Lighting Facts for independent testing, and investigative commissioning authorities’ experience on performance.

The lighting codes have a variety of requirements for controls, which all contribute to a reduction in the total power used by lighting in a facility. The various methodologies permitted, according to the particular spaces, include local switching, automatic switching, daylighting control, two-level switching, occupancy sensors, and vacancy sensors.

Exterior lighting

The type and wattage of exterior lighting fixtures are tightly regulated by the current lighting codes. One of the most restrictive of these regulations is based on the character of the "exterior lighting zone." These zones go from a highly developed, active commercial district to an industrial area to residential to park lands and undeveloped areas, giving a total of 11 zones under ASHRAE 90.1-2013.

IECC 2012 has similar lighting zones that are divided into 10 activity levels. There are multiple lighted areas within each of the zones that have varying restrictions on the lighting wattages for each area. As an example, a parking area in a rural zone has a maximum lighting power density (MLPD) of 0.04 W/sq ft of lighted area. If this same parking area is in a residential or light industrial zone, the MLPD rises to 0.06 W/sq ft; for an active commercial district, the same parking area would be permitted to have 0.13 W/sq ft.

Each of the zones has from 4 to 21 lighting areas permitted for that zone. The type of each zone controls which exterior lighting application is permitted for that zone. For example, sales lot street frontage is permitted 30 W/linear ft in a commercial district, 10 W/sq ft in a residential district, and is not permitted at all in a developed rural area.

Looking toward the future

The goal for lighting power density, based on the Architecture 2030 Challenge, is to sequentially reduce lighting power use from 0.82 W/sq ft today per IECC (or 0.9 W/sq ft per ASHRAE), to 0.75 W/sq ft in 2015, 0.5 W/sq ft in 2020, 0.25 W/sq ft in 2025, and 0.0 W/sq ft in 2030. There are many engineers, architects, equipment suppliers, and contractors that have joined this program and are convinced that these goals are achievable.

With the technology available today, the best efficiency that could be achieved is on the order of 400 lumens/W in usable lighting output. Even with this efficiency (which is about four times the current commercially available LED efficiency), it will not be possible to achieve 0.0 W/sq ft for LPD. Note: It would be interesting to ascertain exactly how the 0.0-W/sq-ft LPD could be achieved; it appears that only the power produced by offsite, carbon-emitting generating stations count toward this goal. If this is the case, then the use of nuclear, wind, water, or photovoltaic electrical power may be used without any limits and still meet the Architecture 2030 goal. It is hoped that ASHRAE and IECC will agree with this approach and allow these noncarbon-emitting power sources to be used and not included in the LPD requirements for the facilities.

Navigating the energy codes of today requires diligence and careful planning. In some jurisdictions, the engineer will find code requirements for the LPD and the required lighting levels for various spaces, and, invariably, it may be very difficult to meet each and every requirement. By careful selection of lighting fixtures and lamp sources, the engineer can provide a pleasant lighting environment that satisfies all of the codes, the owner, and the architect at a reasonable cost.

However, without staying up-to-date on the latest technologies and applying them to the areas in which they are most appropriate, the design can fail to meet the code requirements, cost significantly more than the budget, or provide inadequate or unsatisfactory lighting for the facility.

Kenneth L. Lovorn is president of Lovorn Engineering Associates. He has more than 45 yr of progressive design and engineering management experience with architect-engineers and consulting engineers designing lighting and electrical systems. He is a member of the Consulting-Specifying Engineer editorial advisory board.