Most private buildings fall under Article 320. But certain affordable housing properties and houses of worship may fall under Article 321, which has its own rules, requirements, and compliance options. If your building qualifies under Article 321, you may have an alternative path to compliance. But let’s be clear: Article 321 does not mean you get to ignore LL97. It just means the city gave you a different maze.

What is Article 321?

Article 321 is part of Local Law 97 and applies to certain buildings that are treated differently from standard private buildings under Article 320. Article 321 generally covers:

• Affordable housing properties
• Certain rent-regulated buildings
• Houses of worship
• Buildings with specific housing or occupancy characteristics

Article 321 is supported by DOB rule 1 RCNY §103-17, which explains how the Department of Buildings enforces this compliance pathway.

The big takeaway

Article 321 buildings may have a different compliance path than Article 320 buildings. But different does not mean exempt.

If your building falls under Article 321, you still need to:

• Understand your requirements
• Complete the right work
• Submit the proper report
• Keep documentation in order
• Work with the right qualified professional

Article 321 vs. Article 320

LL97 is broken into different articles because not every building is treated the same way. Here’s the simple version:

• Article 320 applies to most covered private buildings.
• Article 321 applies to certain affordable housing properties and houses of worship.
• Article 320 focuses heavily on annual greenhouse gas emissions limits.
• Article 321 offers alternative compliance pathways, including energy conservation measures.

Who may fall under Article 321?

Article 321 may apply to certain buildings that are not handled the same way as standard private buildings under Article 320.

This can include:

• Affordable housing buildings
• Rent-regulated buildings
• Houses of worship
• Mixed-use properties with qualifying housing or religious use
• Properties with specific ownership, occupancy, or regulatory characteristics

This matters because two buildings can look nearly identical from the sidewalk but have completely different compliance obligations once you review the details. The question is not just: “Does LL97 apply to my building?”

The better question is: “Which LL97 pathway applies to my building?”

What are the Article 321 compliance pathways?

Article 321 buildings generally have two main ways to comply.

1. Performance-Based Compliance

Under this pathway, the building demonstrates that it meets the applicable greenhouse gas emissions limits. This usually means showing that the building’s emissions are within the required limit.

2. Prescriptive Compliance

Under this pathway, the building completes required Prescriptive Energy Conservation Measures, often called PECMs.

Instead of only focusing on whether the building is under an emissions cap, the owner shows that specific energy-saving improvements were completed.

What are Prescriptive Energy Conservation Measures?

Prescriptive Energy Conservation Measures are specific upgrades or improvements that help reduce energy use and emissions.

Depending on the building, these may involve:

• Lighting
• Heating systems
• Cooling systems
• Ventilation
• Insulation
• Domestic hot water systems
• Controls
• Building envelope improvements

The goal is simple: make the building more efficient and reduce waste. The city’s version is less simple, obviously. It involves rules, reports, certifications, and probably at least one spreadsheet that makes someone sigh audibly.

What is the Article 321 deadline?

Article 321 covered buildings were required to submit a compliance report to the Department of Buildings by May 1, 2025. The report depends on which compliance pathway the building follows.

For the prescriptive pathway, the report generally shows that the required energy conservation measures were completed.

For the performance-based pathway, the report generally shows that the building meets the applicable emissions requirements.

Either way, documentation matters.

This is not the kind of rule where “we upgraded some stuff a while back” is enough. The filing needs to match DOB requirements, and the work needs to be properly documented.

Who certifies Article 321 compliance?

Depending on the compliance pathway, Article 321 reporting may need to be certified by a qualified professional. This may include:

• A registered design professional
• A qualified retro-commissioning agent
• A licensed engineer or architect, depending on the filing requirement

The important part to know here is that owners should not treat this as a self-attestation. DOB expects the report to be properly prepared, reviewed, and certified.

Are Article 321 buildings exempt from LL97 penalties?

Not automatically. Article 321 may provide an alternative compliance pathway, but covered buildings can still face enforcement risk if they:

• Fail to submit the required report
• Submit an incomplete report
• Miss required deadlines
• Fail to complete required measures
• Choose the wrong compliance pathway
• Do not maintain proper documentation

The safest move is to confirm the building’s status early, identify the correct pathway, complete the required work, and keep records organized.

Why Article 321 matters for affordable housing owners

Article 321 matters because it may provide a more realistic compliance path for certain affordable housing properties. Instead of forcing every building into the same emissions-limit structure as standard private buildings, Article 321 may allow qualifying buildings to comply through required efficiency measures. That can be helpful. But it is not automatic.

Owners still need to know:

• Whether Article 321 applies
• Which pathway they qualify for
• What work must be completed
• What report must be filed
• Who needs to certify it
• What documentation must be kept

Getting this wrong can lead to missed deadlines, unnecessary penalties, and the kind of last-minute scramble nobody wants.

Why Article 321 matters for houses of worship

Houses of worship may also qualify under Article 321. This matters because religious buildings often have:

• Unique layouts
• Older systems
• Irregular occupancy patterns
• Limited capital budgets
• Mixed-use spaces
• Historic or hard-to-upgrade building systems

A single property may include:

• A sanctuary
• Offices
• Classrooms
• Community rooms
• Residential space
• Event areas

That can make LL97 compliance more complicated than it looks on paper. Article 321 may offer a compliance pathway that better reflects how these buildings actually operate. Houses of worship should not assume they are automatically exempt just because they are religious or nonprofit properties. The building still needs to be reviewed.

Article 321 compliance checklist

If your building may fall under Article 321, start here:

• Confirm whether your building is covered by Local Law 97
• Determine whether Article 320 or Article 321 applies
• Review whether your building qualifies as affordable housing, rent-regulated housing, or a house of worship
• Determine whether your building must meet emissions limits or complete prescriptive energy conservation measures
• Gather energy and building system documentation
• Work with the right qualified professional
• Prepare the required compliance report
• Submit the report to the Department of Buildings
• Keep records in case DOB requests support later

Local Law 97 (Article 321) Prescriptive Measures

§ 28-321.2.2 Prescriptive energy conservation measures. By December 31, 2024, the owner of a covered building shall ensure that the following energy conservation measures have been implemented where applicable:

1. Adjusting temperature set points for heat and hot water to reflect appropriate space occupancy and facility requirements;
2. Repairing all heating system leaks;
3. Maintaining the heating system, including but not limited to ensuring that system component parts are clean and in good operating condition;
4. Installing individual temperature controls or insulated radiator enclosures with temperature controls on all radiators;
5. Insulating all pipes for heating and/or hot water;
6. Insulating the steam system condensate tank or water tank;
7. Installing indoor and outdoor heating system sensors and boiler controls to allow for proper set-points;
8. Replacing or repairing all steam traps such that all are in working order;
9. Installing or upgrading steam system master venting at the ends of mains, large horizontal pipes, and tops of risers, vertical pipes branching off a main;
10. Upgrading lighting to comply with the standards for new systems set forth in section 805 of the New York city energy conservation code and/or applicable standards referenced in such energy code on or prior to December 31, 2024. This provision is subject to exception 1 in section 28-310.3, provided that July 1, 2010 is replaced by January 1, 2020 for the purposes of this section;
11. Weatherizing and air sealing where appropriate, including windows and ductwork, with focus on whole-building insulation;
12. Installing timers on exhaust fans;
13. Installing radiant barriers behind all radiators.

Common mistake: assuming Article 321 means “we’re exempt”

This is the big one. Article 321 does not mean LL97 disappears. It means your building may have a different way to comply.

That difference matters, especially for affordable housing properties and houses of worship. But owners still need to take action, file properly, and document the work.  If you are not sure which article applies to your building, don't guess! LL97 has too many trapdoors for guessing.