ASHRAE 90.1-2022: Six Things You Actually Need to Know

ASHRAE Standard 90.1 has been the foundation of US commercial building energy codes since 1975. The 2022 edition arrived in January 2023 with over 60 addenda, section renumbering that will trip you up at least once, and a fundamental shift from tracking energy costs to tracking carbon emissions. Here are the six changes that will actually affect your work.

1. You Can Trade Off HVAC Requirements Now (Sort Of)

The new Mechanical System Performance Rating method in Appendix L lets you trade HVAC requirements against each other without running a whole building energy model. Missing an economizer because your space configuration makes it impractical? Make it up with higher efficiency cooling equipment or reduced fan energy.

The constraint is you can only trade within the HVAC system. No swapping a better chiller for a worse envelope. Those have different lifespans (15 years versus 40+ years), and the committee finally acknowledged that matters. Currently the method works for office, retail, education, and multifamily buildings. Healthcare systems are too complex. If you need complicated tradeoffs there, you're doing Appendix G regardless.

The metric is called Total System Performance Rating (TSPR). It's set up so higher numbers mean better performance, matching how you already think about COP and EER. You get credit for part-load performance, which is where equipment actually operates most of the time. PNNL developed a compliance tool that uses simplified block modeling. Early users say the interface is reasonable, which is higher praise than it sounds.

The method compares your proposed design to a reference system with performance equivalent to the 2004 version of the standard, adjusted by a Mechanical Performance Factor for your climate zone and building type. All the complex bits happen in software. You just input your design and see if it beats the target.

2. Energy Credits Give You Actual Flexibility

Section 11 (formerly known as "the section that didn't exist") introduces energy credits as a compliance path. Pick from 33 measures covering efficiency improvements, renewable energy, and load management. Most building types in most climate zones need 42 to 50 credits total. Each credit represents one-tenth of one percent of whole building energy cost, targeting 5% overall savings beyond base prescriptive requirements.

This matters because prescriptive requirements have to work for every building, which means they're often not optimized for your specific project. Energy credits let you pick measures that make sense for your building type, climate, and budget. Some credits have fixed values. Others scale based on how much you exceed minimums, so you can earn extra points for going beyond the base threshold.

Credits cover envelope performance improvements, HVAC efficiency upgrades, service water heating, additional on-site renewables beyond the new prescriptive minimums, peak load management, and automatic shading systems. The new version of COMcheck integrates credit calculation directly. When you input lighting fixtures, it determines whether you earn reduced lighting power credits. When you document HVAC equipment, it calculates performance improvement credits automatically.

PNNL analyzed cost effectiveness for each building type to ensure credit packages make economic sense. The standard is on continuous maintenance, meaning anyone can submit proposals for new credits. If you represent a manufacturer with an innovative technology that's cost-effective for some buildings but not all, energy credits provides a home for it. Contact the committee for help developing the credit calculations. They do the prototype modeling.

3. On-Site Renewables Are Now Mandatory

Section 10.5.1 establishes a prescriptive requirement for on-site renewable energy. Buildings meeting size and occupancy criteria must provide either 0.5 watts per square foot or 1.7 BTUs per square foot of renewable capacity based on gross floor area of the first three floors.

The calculation is straightforward. Take your building's gross floor area for floors one through three (high-rises don't get penalized), multiply by 0.5 W/sf, and that's your renewable capacity requirement. A 50,000 sf single-story warehouse needs 25 kW. A ten-story building with 5,200 sf floor plates needs 7.8 kW (15,600 sf total for three floors). A two-story school with 26,000 sf per floor needs 26 kW.

Exceptions exist for green roofs (don't want to conflict with stormwater management goals), buildings shadowed by taller structures nearby (demonstrated through solar access analysis), and alterations. The logic is reasonable. If your building sits in the shadow of a 40-story tower, rooftop PV isn't accomplishing much.

For performance modeling, ECB handles this by modeling the same renewable type in the baseline if your proposed design includes renewables. If you don't include renewables in your proposed design, a default PV system goes in the baseline configured per NREL's PV Watts assumptions. Appendix G doesn't model any renewable in the baseline regardless of your proposed design.

This is the first time 90.1 has required on-site renewables prescriptively rather than as an optional credit or tradeoff. It reflects the shift from energy efficiency to decarbonization as the primary policy goal.

4. Equipment Efficiency Changed (And Refrigerants Are Phasing Out)

Multiple equipment tables updated, but the big changes are metric conversions and refrigerant phase-outs that affect every piece of HVAC equipment you specify.

Residential and light commercial equipment switched from SEER to SEER2 and HSPF to HSPF2 as of January 1, 2023. The new metrics include higher external static requirements (0.5 inches versus 0.1 to 0.2 inches previously), which dropped ratings about 5%. But actual efficiency requirements went up, so a 15 SEER2 requirement equals roughly 14.3 old SEER after the derate. Commercial three-phase equipment follows January 1, 2025.

VRF equipment got hit with sensible heat factor requirements at 100% and 75% capacity per AHRI 1230-2021. This dropped EER ratings 4.2% to 6.7%, but manufacturers absorbed the change while simultaneously improving actual efficiency about 12%. Your equipment appears less efficient on paper while performing better in reality, which is confusing but ultimately good.

Coming in 2029 are completely new metrics for commercial rooftops: integrated ventilating energy efficiency (iVEEC) for cooling and integrated ventilating heating efficiency (iVHE) for heating. These include economizer performance, ventilation loads, and crankcase heater power in the ratings. Expect 16% to 36% efficiency improvements. Start planning specifications now because your go-to rooftop unit might not meet the new numbers.

The elephant in the room is refrigerants. EPA's final rule phases out R-410A, R-134A, R-404A, and similar refrigerants effective January 1, 2025 for most equipment, 2026 for VRF. The US signed the Kigali Amendment requiring global warming potential below 750. About 12 states adopted earlier. Every piece of refrigeration equipment gets reformulated. AHRI has recorded webinars explaining what's changing and which replacement refrigerants work in which applications. Watch them before you specify anything with a compressor.

This isn't an ASHRAE change, but it affects every project touching 90.1, so you need to know it's happening.

5. Air Leakage Testing Is Required for Small Buildings

Addendum t makes blower door testing mandatory for buildings under 25,000 sf. Previously you could install a continuous air barrier, conduct visual inspections, call it compliant, and move on with your life. Now you need to actually test and hit 0.35 cfm per square foot at 75 Pascals.

That target isn't Department of Defense stringent (0.15 cfm/sf) but it's real. Exceptions exist for certain building types and configurations, but the basic principle is small buildings need measured air leakage verification. The committee's logic is straightforward: building envelopes last 40+ years while mechanical systems last 15. Making bad envelope decisions for short-term compliance convenience creates buildings that waste energy for decades.

Air leakage testing isn't tradable. You just have to meet it. This represents a significant shift in how envelope performance gets verified. If you design small commercial buildings, expect your envelope detailing to matter more than it used to, and someone's actually going to measure whether it works.

6. Thermal Bridging Requirements Close the Loophole

Addendum av finally addresses thermal bridging, which had effectively been a code loophole. ASHRAE developed detailed methodology for calculating thermal bridges across five categories: roof-to-wall connections, floor balconies and intermediate floors, cladding support systems, window frames, and major penetrations (canopies, signage, structural elements).

The requirements include default psi factors for linear thermal bridges and chi factors for point thermal bridges. If you don't want to calculate everything from first principles, the standard provides suggested constructions and default values you can reference. The catch is you actually have to address it now rather than pretending thermal bridges don't exist because they're hard to calculate.

Thermal bridging is in the tradable section of the code, meaning you can skip it if you compensate elsewhere. But you need to demonstrate that compensation using the Appendix C envelope tradeoff method in COMcheck. You can't just ignore it and hope nobody notices. The typical tradeoff is better windows or additional wall insulation to make up for thermal bridge losses you're not addressing.

The standard added an entire appendix of figures and details because explaining steel-to-steel connections and concrete attachments with words alone doesn't work. These are the kinds of connections where insulation gets interrupted and heat finds a path through your envelope. Balconies cantilevered through wall assemblies. Structural steel penetrating insulation layers. Cladding clips creating repeating thermal shorts.

The building industry has known about thermal bridging for decades. We just collectively agreed not to deal with it because the math was annoying and it made detailing more complicated. The 2022 standard ended that arrangement. You can still choose not to address thermal bridging in your design, but you have to compensate for it somewhere else in the envelope performance. The heat loss doesn't magically disappear just because you didn't model it.

This pairs with the air leakage testing requirements to significantly tighten envelope performance verification. The combination means your envelope detailing matters more than it used to, and you can't trade your way out of both requirements simultaneously.

What Else Changed

Chiller performance curves got standardized in Appendix J, fixing the problem where every engineer used different part-load curves and nobody's results matched. Building Performance Factors updated to reflect more accurate baseline modeling, making many of them less stringent even though the standard improved overall. Retrofit provisions differentiate between substantial alterations (following new building rules with 5% relaxed targets) and minor alterations (baseline to existing conditions for unaltered areas).

Section numbering changed. Energy Cost Budget moved from Section 11 to Section 12. Energy credits took Section 11. References moved to Section 13. This will cause at least one embarrassing moment in a meeting when you reference the wrong section from muscle memory.

Adoption Status

Oregon adopted 90.1-2022 directly as of January 1, 2025. Illinois, Nevada, North Dakota, and Rhode Island adopted IECC 2024, which allows 90.1-2022 as an alternative. Austin, Phoenix, and Nashville follow mid-2025. New York adopted it with state modifications effective December 31, 2025, including fossil fuel prohibitions currently suspended by court order.

About 14 states require the 2019 version. Colorado, Wyoming, the Dakotas, Kansas, Missouri, and Mississippi have no statewide commercial codes. The federal government adopted 2019 for HUD and USDA programs with 2022 as an acceptable alternative.

The standard is available at ashrae.org with complete addenda documentation. DOE estimates 14% energy savings over the 2019 edition, 19% cost savings, and 48% improvement compared to 2004. States and jurisdictions are adopting it faster than previous editions, which suggests the flexibility mechanisms (energy credits, MSPR) are actually useful rather than just additional compliance burden.

Whether the industry hits the 2030 to 2050 net zero targets depends on factors well beyond building codes. But the framework is operational and the requirements are moving in the right direction.