BY Craig DiLouie, LC, CLCP, education director for the Lighting Controls Association
Next year, the 2019 version of ANSI/ASHRAE/IES 90.1, Energy Standard for Buildings except Low-Rise Residential Buildings, takes effect as the national energy reference standard. This is based on a July 2021 Department of Energy (DOE) ruling that determined the standard saved more energy than the preceding 2016 version. By July 28, 2023, all states must adopt a commercial building energy code at least as stringent as the standard, or justify why they cannot comply.
What does this mean in your jurisdiction?
Intro to energy codes
Commercial building energy codes regulate the energy-efficient design of nonresidential buildings, enduring as a highly effective policy to achieve energy savings. They are implemented by jurisdictions, which may be a state, city, federal building, etc.
Implementation and compliance across the country can be complex, as you might find:
Model codes and standards: A majority of states with commercial building energy codes base them in whole or in part on an energy standard or model code. The primary model codes and standards are ANSI/ASHRAE/IES 90.1 produced by ASHRAE and IES and the International Energy Conservation Codes (IECC) produced by the International Code Council. They contain similar but not always the same requirements regarding the design of building systems like lighting.
Note each is updated every three years respectively by ASHRAE/IES (…2016, 2019, and soon 2022) and the International Code Council (…2015, 2018, 2021), and there may be amendments. Therefore, designers must keep abreast of code changes adopted by their jurisdiction and become aware of code differences if working across multiple jurisdictions (different states, cities, counties, etc.) that may have different codes.
Of the two, the IECC is more popularly adopted, though it references 90.1 as an alternative compliance standard. While not the same document, 90.1 influences IECC development due to pressure to harmonize, resulting in similar requirements roughly aligning across versions over time. And as the national energy reference standard recognized by the DOE, 90.1 is referenced by building rating systems such as LEED, federal building programs, and more.
Image courtesy of the Department of Energy
State-specific codes: This is an energy code written by the jurisdiction. Though it may contain similar requirements as model codes, it is unique. An example is California’s Title 24, Part 6 energy code.
No statewide code: Some states have no statewide code, such as Colorado, whose home-rule constitution does not grant the state government the authority to enact one. In this case, the designer may need to comply with energy codes implemented at the county and smaller level, which may further granularize the task of compliance.
DOE ruling and impact
The Energy Conservation and Production Act authorized the DOE to determine whether the latest version of 90.1 (for commercial and multi-family high-rise residential buildings) will improve energy efficiency compared to its previous version. The DOE has one year after publication of the latest version of 90.1 to accomplish this. (A similar residential energy code determination is made for IECC for low-rise residential buildings but is outside this article’s scope.)
On July 28, 2021, the DOE issued a determination that ANSI/ASHRAE/IES 90.1-2019 achieves greater energy efficiency in buildings covered by the standard than the 2016 version. The DOE estimated national savings in commercial buildings of approximately 4.7% site energy, 4.3% source energy, 4.3% energy cost, and 4.2% carbon emissions.
As a result, states were given two years to adopt a commercial building energy code at least as stringent as 90.1-2016 or justify why they cannot comply. A handful of states are already in compliance, as shown below.
Image courtesy of the Department of Energy
The DOE ruling is likely to result in gradual adoption of more stringent codes based either on 90.1-2019 or a recent version of the IECC.
Once robust, compliance with these rulings has become fragmented and slow, resulting in the United States being a patchwork of codes based on whether it’s a state-specific or a model code, which model code has been adopted, and which version of that model code is used.
Lighting changes in 90.1-2019
ANSI/ASHRAE/IES Standard 90.1-2019 includes more than 100 changes from the 2016 version, covering administrative and enforcement, commissioning, mechanical, and lighting.
For lighting, the new version adjusts interior power allowances, updates several control requirements, and introduces a simplified compliance method for office, school, and retail buildings.
The standard imposes a mix of prescriptive and mandatory requirements, with prescriptive requirements focused on lighting and mandatory requirements focused on lighting controls. Since 1999, the overall trend is toward lower power allowances as energy-efficient traditional and then more-efficient LED technology developed, as well as more intensive controls to maximize energy savings. The 2019 version of 90.1 is no exception, with changes focused on tightening interior power allowances while tweaking requirements for lighting controls.
A more recent trend in energy codes is to maximize energy savings by maximizing adoption via simplicity, and another is more emphasis on existing buildings. These trends are in evidence in 90.1-2019, notably via the introduction of a new, simplified compliance path for smaller office, school, and retail buildings, well-suited to contractors and many designers.
Let’s take a deeper look at what’s new.
Lighting power
The 90.1 standard separately caps interior and exterior lighting power density.
Interior lighting power: Unless choosing to use complex building modeling, designers can design interior lighting systems toward one of two compliance paths:
Building Area Method: single maximum power allowance in W/sq.ft. for entire building.
Space by Space Method: maximum power allowance for each type of space within building.
The 2019 version of 90.1 adjusted these power allowances based on modeling in turn based on the latest IES recommendations. For interior lighting power, allowances were raised in a few cases but generally reduced.
Looking at the Building Area Method, lighting power allowances were increased for several building types, including automotive, exercise center, gymnasium, library, parking garage, and workshop. The rest, however, were reduced, modestly in some cases and with much deeper reductions in others.
Some examples are shown below.
| Building type | 90.1-2016 | 90.1-2019 | Change |
| Office | 0.79W/sq.ft. | 0.64W/sq.ft. | -19% |
| Retail | 1.06W/sq.ft. | 0.84W/sq.ft. | -21% |
| School/University | 0.81W/sq.ft. | 0.72W/sq.ft. | -11% |
| Hospital | 1.05W/sq.ft. | 0.96W/sq.ft. | -9% |
| Manufacturing | 0.90W/sq.ft. | 0.82W/sq.ft. | -9% |
| Warehouse | 0.48W/sq.ft. | 0.45W/sq.ft. | -6% |
Exterior lighting power: The standard also caps exterior lighting power, though power allowances are largely unchanged in the 2019 version of 90.1.
The standard added a provision for calculating the power allowance for applications not listed in the table or not comparable with any listed on the table.
New compliance path
For buildings in which at least 80% of the floorspace is used as an office, retail, or school building, ASHRAE/ANSI/IES 90.1-2019 offers a new, simplified Building Area Method. This compliance path can be used for interior and exterior lighting (though calculated and complied with separately) for new buildings and tenant improvements under 25,000 sq.ft.
Compliance: The designer consults a series of tables listing various applications in office, retail, and school buildings along with maximum lighting power allowances and applicable mandatory control requirements. Another table lists exempted lighting applications across all three building types.
The idea here is to simplify compliance for smaller, common buildings. The designer complies by satisfying a relatively stringent lighting power allowance along with some fundamental controls such as automatic shutoff, manual local control, bilevel control, partial-OFF lighting in stairwells and corridors, and, in retail buildings, daylight-responsive dimming.
Existing construction: A notable exemption in this section is luminaire and lamp/ballast replacements, in which compliance may be gained by ensuring a minimum power reduction of at least 35% for existing fluorescent T12 systems, 20% for T8 or T5, 45% for high-intensity discharge (HID), and 75% for incandescent. While controls are not mentioned as part of this exception clause, note that earlier in the standard’s lighting section, either compliant occupancy- or time-based automatic shutoff controls are required if more than 20% of the connected lighting load is being replaced as part of the lighting upgrade.
Lighting controls
ASHRAE/ANSI/IES 90.1-2019 version updated the energy standard’s lighting control requirements for parking garages to account for the use of LED technology, updated daylight-responsive control requirements, and added a definition of “continuous dimming” based on NEMA LSD-64-2014.
Parking garage control: Parking garage lighting has its own particular control requirements, and the 2019 version requires lighting power for each luminaire to be reduced by at least 50% when no activity is detected for 10 minutes. Parking garage transition lighting is also addressed.
Daylight-responsive control: Sidelighting requirements and associated exceptions are clarified in the 2019 standard. In all daylight areas, the photocontrol must reduce lighting power via continuous dimming and in response to daylight by at least 80%, including OFF. If another partial-OFF control reduces lighting power, the daylight-responsive control can adjust in response to daylight but may not increase power above the partial-OFF control level.
For toplighted spaces, similar to requirements already in effect for sidelighted spaces, calibration control must be located 11 ft. or lower above the finished floor, and must not require the physical presence of a person at the sensor while the processing takes place.
Commissioning: Commissioning must be undertaken in accordance with the lighting section as well as relevant subsections of Section 4.2.5, which contain new building commissioning requirements conforming with ASHRAE/IES Standard 202.
90.1 decoded
Overall, ASHRAE/ANSI/IES 90.1-2019 is tougher on interior lighting power allowances, tweaks already stringent control requirements, ties all commissioning activities into a series of building commissioning activities, and attempts to simplify compliance for certain building types.
Now recognized by the DOE as the new national energy reference standard, adoption will likely increase in 2023 and beyond. As such, it may be useful to gain familiarity with its changes now.
For a complete representation of the standard, consult ASHRAE/ANSI/IES 90.1-2019, available at the ASHRAE bookstore here. For interpretations, consult the standard or the authority having jurisdiction.