Industrial Utility Efficiency

ASHRAE 90.1 Brings New Requirements to Compressed Air System Design

The energy efficiency standard adds compressed air specs for the first time, bringing engineers into system design

Word is beginning to filter out about the 2022 changes to the ASHRAE 90.1 energy efficiency standard, and the changes it promises to bring to how compressed air systems are specified, commissioned and maintained. More specifically, the industry is learning about section 10.4.6 of 90.1, which is the first time the standard has included a section on compressed air. 

ASHRAE, the American Society of Heating, Refrigeration and Air-Conditioning Engineers, was founded in 1895. Part of the association’s mission is to create standards that give guidance to U.S. construction. The 90.1 standard covers all sites and buildings except for low-rise residential buildings, and offers engineering firms minimum requirements for energy-efficient buildings. It includes chapters on the building envelope; heating, ventilating and air conditioning; service water heating; power; lighting and more. It was first created in 1975, and in 1992 it was included in the Energy Policy Act by Congress, giving it jurisdiction over much new construction. 

As of January, 2023, the 90.1-2022 standard includes a new section numbered 10.4.6 that falls in the Other Equipment chapter, which also covers elevators, escalators and air curtains. The 10.4.6 section brings compressed air systems into this engineering almanac for the first time. Compressed Air Best Practices spoke to Richard Lord, ASHRAE fellow, committee chair of the 90.1-22 committee, and a senior fellow with Carrier, and Susanna Hanson, CEM, DGCP, director and regional chair of ASHRAE Region VI and principal R&D engineer and scientist for Honeywell, to learn why this section was added and what it means for compressed air system design.

“Compressed air systems were added because compressed air can use a lot of energy, especially if it's not well-maintained,” explains Lord “Having worked in a lot of manufacturing plants, maintenance of compressed air systems can be a very important thing to do. So we focus on picking some of those requirements.“

The 90.1 standard is a combination of prescriptive and mandatory specifications. Any 90.1 section with a dot-four in it is mandatory, while dot-five sections are prescriptive, meaning the standard proposes one way of doing things, but engineers are free to differ. Also, 90.1 is a continuous maintenance standard, and will be modified and republished every three years, meaning 2025, 2028, and 2031 will see updated versions. ASHRAE forms its standards by setting a goal of a certain level of energy improvements. For the 2022 standard, the goal was to improve energy efficiency by 45% over the base year of 2004. The 10.4.6 section might be just a page-and-a-half (side the sidebar for details about what it includes), but it’s supported by detailed addendums and technical documents. 

“We have to prove cost justification,” Lord says. “So we have an economic justification that shows that this will pay back in the life of the building or the life of the equipment. A lot of our equipment, at least the mechanical equipment, is also reviewed by the Department of Energy. So the Department of Energy has a mission to improve building efficiency that's defined by them under the Energy Policy Act of the United States.”

The 10.4.6 section includes specifications on part-load efficiency, controls, monitoring, leak testing, and pipe sizing. 

Lord notes that the inclusion of monitoring can be hard to justify since it doesn’t directly save energy, but it’s useful for spotting problems before they get out of hand: "Hey, why is my energy in my compressed air system 20% greater this month than it was last month? Maybe we have a leak someplace."


Richard Lord                                                                   Susanna Hanson


 “We have to prove cost justification. So we have an economic justification that shows that this will pay back in the life of the building or the life of the equipment.”—Richard Lord


No Love for New Regulations

California gets the credit for introducing legislation on air compressor efficiency, Lord says. “They start to look at their energy use and they say, ‘Well, hey, here's an area that we have not tapped into." When you look at a manufacturing facility, compressed air is 20%, 30% of the energy load. What can we do to reduce that, just like we try to reduce the heating load, we try to reduce the cooling load?”

For those already chaffing at the idea of new regulations telling them how to do their work, it’s useful to think of 90.1 as guidance and goals. “I hate people to tell me how to design my HVAC system or design my compressed air system. But if we can set goals and we can set metrics, then our firm can come in and say, ‘My new system is 20% more efficient than the system you have in there.’ It gives you a way to sell new products and upgrade systems.”

Are these specifications mandatory? What happens to firms that choose not to follow them? The answer is it depends. As Hanson points out, there are no police enforcing this. Even though some of the code is specified as mandatory, there’s no enforcement built in. This is the standard of care for engineering professionals, she notes, and they’re expected to design to these standards. If they aren’t followed, the Department of Energy might recognize that some states are lagging in their energy efficiency goals and make an effort to get those states up to the level of the other states. With that said, some parts of the country make 90.1 compliance a prerequisite for getting building permits, so building without following the standard’s specs wouldn’t be possible.

“Manufacturers don't really like having multiple rules in different jurisdictions, and so manufacturers typically will also drive a harmonization by just having products that meet whatever the manufacturer can do,” Hanson says. “There's a lot in here that the engineer has to do, but the parts that are done by manufacturers, a lot of times that gets done for the states. The market kind of moves almost in a disjointed way from where the codes are, just by virtue of wanting to have economies of scale, and the production of that equipment.”


Enter the Engineer

One result of the addition is that engineers will now likely play a larger role in planning compressed air systems, which could lead to integrated heat recovery solutions that harness and use the energy now lost to heat of compression. As Hanson notes, there have now been a generation or two of engineers who don’t have much to do with the compressed air sides of commercial buildings, their compressed air skills having atrophied after buildings went from using pneumatic controls to electrical controls. Smaller engineering firms may not have compressed air knowledge, but instead rely on the major compressed air manufacturers to design their systems. 

“I think the same, more or less, happens in grocery refrigeration as well, where the manufacturers of the equipment assemble an engineering department that's registered in every state that they do business, and they do the designs,” Hasson says. “I think there are elements of the industrial space that have been requiring the manufacturers of their systems to basically do designs for free, or as part of their regular cost of doing business, so what they charge for the equipment is also rolled into that. Maybe the more efficient way to do it is rather than educate every consulting engineer, you just educate the big manufacturers of this equipment and they do it that way. This becomes their standard practice. That would be potentially a faster way to move.”

The inclusion of 10.4.6 to 90.1 is a first take at developing engineering guidelines for compressed air systems, but ASHRAE leadership is interested in refining its codes through feedback. Readers of Compressed Air Best Practices are welcome to get involved. 

“This is our first shot at trying to put some regulations in there, but we have a process called a continuous maintenance proposal (CMP) process, which is a change proposal process,” explains Lord. “Anybody in the industry can submit a change to 90.1 and then the committee will evaluate it. A lot of times what we do is we'll add on technical experts. So if you guys said, ‘We'd love to help you guys come up with a better compressed air section in the standard,’ we can bring you on as technical experts and we can form a sub-working group.”

Readers who want to take Lord up on this and get involved can do so by submitting a continuous maintenance proposal at A login is required.

“Saving energy has its own rationale,” Hanson says. “It's not just for meeting code and doing what you have to do. 90.1, if you use it right, is a great roadmap for doing things that are cost justified, and are easier to get through your process internally, your process externally. It gives you air cover for chartering projects.”


A Closer Look at Section 10.4.6 on Compressed Air System Design

ASHRAE doesn’t allow its standards to be reprinted, but the following paraphrase explains what section 10.4.6 of the 90.1-2022 standard contains. For the exact wording, visit

10.4.6 The introduction explains that these requirements apply to compressed air systems in industrial locations, and apply to air compressors and related piping and controls but not to systems that use that compressed air. The title of this part is Part-Load Controls and Efficiency. It requires that compressed air systems of 25 hp or more need to include one or more trim compressor(s) and primary storage. It then provides two options for compliance.

Option 1 says the system shall include one or more VSD air compressors. It provides sizing guidelines for trim compressors and primary storage. Option 2 requires that the total effective trim capacity of an air compressor system is within certain specific power (kW/100 acfm) parameters. 

This part also includes exceptions to its trim requirements, which include systems that have been altered in specific ways or that include centrifugal compressors. This part mandates the uses of energy-saving controls on systems that include three or more air compressors (including backups) with a total input power of over 150 hp. This part mandates an energy and compressed air demand monitoring system for systems with input power of 150 hp or greater. The monitoring system needs to measure system pressure, measure or calculate current or power per air compressor, and measure or determine total airflow from all air compressors in acfm. 

Data logging is required for a list of key performance indicators at intervals of five minutes or less. The equipment shall record not less than six months of data and provide exportable data. A visual trending data display is also required. Piping leak testing is mandatory. This part explains how compressed air system piping shall be pressure tested with a pressure loss requirement of equal to or less than 1.0%. For piping less than or equal to 50 feet in length, connections may be optionally tested with specific methods. The last section includes specifications for pipe sizing. For new systems and additions to systems, the guideline for headers and distribution piping is to minimize frictional losses. For service line piping to end uses, piping inner diameters shall be greater than or equal to 1 inch. Replacement piping in existing systems shall also meet these requirements. 


To acquire the full 90.1-2022 standard, visit



ASHRAE, founded in 1894, is a global society advancing human well-being through sustainable technology for the built environment. The Society and its members focus on building systems, energy efficiency, indoor air quality, refrigeration and sustainability within the industry. Through research, standards writing, publishing and continuing education, ASHRAE shapes tomorrow’s built environment today. For more information, visit

To read articles on Compressed Air Energy Management, visit

For expert presentations, visit our Webinar Archive Section dedicated to Air Compressor Technology at