Energy standards are a large component in building planning and design for new construction and renovation projects. These guidelines ratchet up building performance over time with regular revision cycles that recognize improvements in equipment.

The latest version of one of the two most important energy standards, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1, is just beginning to show up on the radar of local code officials. For those in the lighting industry, this edition marks a milestone in the development of LED technology, as the standard’s lighting-energy targets are, for the first time, entirely based on LED lamps and fixtures.

This shift illustrates the enormous strides LED product manufacturers have made in a little over a decade. Today’s offerings are more than just highly efficient light sources. In almost all cases, they also surpass their incandescent and fluorescent counterparts in lifespan, controllability and color-rendering. They have already played a big role in driving down lighting’s contribution to overall building electricity use, from 40% in 2005 to 6%–8% today, according to Illuminating Engineering Society (IES) figures. As this most recent version of the ASHRAE standard shows, the technology still has the potential to drive lighting-related energy use down even further without significant first-cost impacts.

What is ASHRAE 90.1?

ASHRAE 90.1, with the official mouthful of a title, “Energy Standard for Buildings Except Low-Rise Residential Buildings,” is one of two major energy standards in the United States—the other is the International Energy Conservation Code (IECC) from the International Code Council. Generally, state and municipal officials turn to one of these documents as foundations for the energy requirements outlined in their own building codes.

While more jurisdictions have adopted the IECC, ASHRAE 90.1 remains relevant even in those locales because the IECC references the ASHRAE standard as an acceptable path for meeting its own requirements. Additionally, the U.S. Department of Energy recognizes ASHRAE 90.1 as the national reference standard.

ASHRAE’s standard is revised every three years, but that doesn’t mean state and municipal codes update automatically in lockstep. In fact, many states and municipalities are still using the 2013 edition. Instead, code authorities independently decide when they want to adopt a new version of either the IECC or ASHRAE standards. There’s often at least a year between a new revision’s publication and its adoption, even in the most progressive jurisdictions, which is why ASHRAE 90.1-2019 is a topic of conversation today, even as the 2022 edition nears its own publication date.

Lighting requirements in ASHRAE 90.1 are defined in terms of lighting power density (LPD), which basically translates into the number of watts used to illuminate a square foot in a space or building type. LPD targets dropped markedly in the standard’s 2016 release as LED products began to penetrate the market. They fell even more sharply in many applications in the 2019 edition, as LEDs became the baseline for calculating what was commercially feasible in terms of lighting-related energy efficiency improvements.

Open-office space offers a strong example of how significantly the move to LEDs improved fixture and lamp efficacy. LPD allowances in these areas under ASHRAE 90.1-2019 are 19%–25% lower than those in the 2016 edition, when fluorescent and incandescent products were still a part of the baseline mix. Retail allowances also dropped substantially, by some 14%–20%, compared to 2016’s targets.

The standard’s developers clarify that, although the stricter efficiency requirements might seem dramatic, they shouldn’t be hard to reach.

“ASHRAE 90.1 is a minimum standard—it’s meant to establish a minimum goal, not a stretch goal,” based on commercially available products, said Mark Lien, industry relations manager for IES and a member of the ASHRAE 90.1 Executive Committee and Lighting Subcommittee that worked on the update.

How updates happen

To understand the reason for the big drop in LPD limits, it helps to know how the lighting portion of 90.1 is updated. Developers start revisions soon after a new edition is released. So, work on the 2019 edition began in the fall of 2016.

As a first step, these lighting industry professionals review how the standard defines various building spaces in terms of typical room sizes, surface reflectances and other characteristics. Another important data point is represented by the lighting levels the IES determines are appropriate for each of those spaces. Then they assemble a list of fixture types that might be used in each space—for example, troffers and cove fixtures in open-office settings or downlights and spots in retail applications. Following on that effort, they look deeper into optional features that manufacturers might have available, including lenses and other optics-enhancers that could affect fixture output.

With this information in mind, developers then identify the multiple manufacturers producing each of the fixture types to develop a “composite” fixture that represents where the market is. This hypothetical product’s averaged performance specifications represent what’s readily available for contractors and lighting designers at the time the data is assembled. This information is typically gathered in the last year of the three-year cycle, which means standard performance might advance further by the time that revision is published.

The lag between data gathering and publication, along with the need to draw on products that represent what’s currently available for purchase, explain why LPDs dropped so significantly between 2016 and 2019. This trend began with the 2016 edition—that’s when LEDs began affecting the standard’s LPD allowances in several spaces. These products were more of a niche offering during the 2013 cycle, when fluorescent and incandescent lamps and fixtures still ruled the market.

“It really comes down to LEDs; they are a lot more effective,” said Eric Strandberg, senior lighting specialist with the Lighting Design Lab run by Seattle City Light, the city’s municipal utility, when describing the technology improvements that have driven lighting’s power requirements downward. “I think there’s also been better lensing, and then the third big piece is controls.”

ASHRAE 90.1’s 2016 release still included some incandescent and fluorescent products in its baseline for space categories such as retail, where the older technologies still performed better in terms of characteristics such as color rendering that were important to the market.

Of course, one reason for the move away from incandescents and fluorescents is the result of federal lumens-per-watt efficiency standards that the older technologies simply can’t meet. But LED manufacturers also have made enormous technology improvements over the last two cycles for the standard.

One example of this move forward can be seen in the shift in assumptions regarding lumen depreciation between 2016 and 2019. In 2016, developers calculated that LED products’ output would decline to 70% of original performance over the course of their useful lives. During the 2019 revision cycle, they determined this figure overstated the output drop, which had improved to 85% of original levels by the end of useful life.

What’s next

The lighting subcommittee for the ASHRAE 90.1 2022 edition has its draft out for final comments now and anticipates an October release, according to Mike Houston, director of Atrius Applied Solutions (an Acuity Brands subsidiary) and a voting member on the lighting subcommittee and the full ASHRAE 90.1 project committee. He and IES’s Lien suggest designers and contractors can expect LPD targets to drop further in this year’s version for most categories, though a few applications could see an increase in allowances. More attention might be paid to controls, though, with LPD credits possibly being available when certain controls are in place.

What primarily stands in the way of future LPD reductions being as dramatic as those that occurred between 2016 and 2019 is the issue of diminishing returns. Although manufacturers seem to push lamp and fixture efficacy—the amount of light produced in lumens, per unit of electricity in watts—to new highs every year, at a certain point, the incremental reductions in energy use won’t make enough difference to force the market to push it down further.

“The quantum leap was going to LED technologies—and one reason efficacy of LEDs isn’t rising as fast as it used to is that the market has accepted the price and performance that’s already there,” Strandberg said, adding that there also will come a point where efficacy simply can’t be pushed higher. “We may be getting to the point where the lighting power with LEDs is so low that we don’t have to cut it as much, going forward.”

Houston said there’s still room for improvement, but that other factors beyond pure efficacy also required attention.

“The functional efficacy limit we tend to put at 200 lumens per watt, but there’s a balance between lumens per watt and lumens per dollar,” he said.

He added that, in some applications, factors such as color rendering and overall brightness need to play a more important role in standard setting. However, Houston also seems to be pleased with what’s been achieved so far with LEDs in terms of performance and affordability—especially since this relatively new technology was once seen as a budget-buster.

“The quality of the light has improved with its intensity and its sparkle, and for the first time, lighting prices continue to drop—the lumen-per-dollar is really working to the consumer’s benefit,” he said, noting the changes he is seeing as early adopters have begun updating first-generation products with today’s offerings. “It has been exciting to take out the old LEDs and put in new lights for the same fixture with 40% energy savings.”