Why BAS Compliance Is Now a Core Facility Management Obligation
Energy codes now require a long list of HVAC control functions -- setback, optimum start, supply air temperature reset, static pressure reset, demand-controlled ventilation, economizer high-limit control, and more. In most commercial buildings of meaningful size, the building automation system (BAS) and its direct digital control (DDC) programming are how those functions are delivered. California's 2025 energy code goes further and ties DDC programming itself to ASHRAE Guideline 36.
For facility managers, this has practical implications. A building can have efficient mechanical equipment and still underperform an energy code's intent if control sequences are wrong, DDC programming is incomplete, or overrides left from construction were never removed. The BAS is the evidence that the HVAC system is operating the way the code expects.
This guide covers the control areas that draw the most attention: ASHRAE Standard 90.1 Section 6 controls provisions, ASHRAE Guideline 36 sequences of operation, demand-controlled ventilation (DCV), economizer controls, and Section 8 electrical energy monitoring. California's 2025 Title 24 requirements are covered as an example of where controls requirements are heading.
About Section Numbers
Section numbers below follow the 90.1-2019 numbering used in the U.S. DOE Building Energy Codes Program's 90.1-2019 HVAC training. Your jurisdiction may have adopted 90.1-2019, 90.1-2022, the newer 90.1-2025, or an IECC edition with its own numbering, so confirm section numbers and thresholds against the edition your building was permitted under.
ASHRAE 90.1: The Mandatory Controls Framework
What Section 6 Actually Requires
ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings, is the national model energy standard for commercial buildings. ASHRAE's newest edition is 90.1-2025, but jurisdictions adopt editions on their own schedules, either directly or through the International Energy Conservation Code (IECC), so many buildings are governed by 90.1-2019 or 90.1-2022.
Section 6 of the standard governs heating, ventilating, and air-conditioning systems. It contains mandatory provisions, which apply regardless of the compliance path chosen, as well as prescriptive provisions. Many of the controls requirements facility managers care about are in the mandatory provisions of Section 6.4.3.
When DDC Is Required
Section 6.4.3.10 requires DDC in the applications and under the qualifications listed in Table 6.4.3.10.1. As reproduced in an energy code that adopts the table (New York City's 2025 Energy Code), the new-building triggers include air-handling systems serving more than three zones with fan power of 10 bhp or more, and chilled-water or hot-water plants serving more than three zones with capacity of 300,000 Btu/h or more; separate triggers apply to alterations and additions. Confirm the table in your adopted edition.
Where DDC is required, Section 6.4.3.10 requires the system to be capable of monitoring zone and system demand for fan pressure, pump pressure, heating, and cooling; transferring demand information from zones to air-distribution controllers and from air systems to plant controllers; automatically detecting zones that may be excessively driving reset logic and alarming the operator; and letting the operator readily remove zones from a reset algorithm. In new buildings, the DDC system must also be capable of trending and graphically displaying input and output points.
Key Controls Provisions in Section 6
| Control Function | ASHRAE 90.1 Section (2019 numbering) | Practical Compliance Action |
|---|---|---|
| Zone thermostatic controls and dead band | Section 6.4.3.1 | Where required, maintain at least a 5°F dead band between heating and cooling |
| Off-hour controls (automatic shutdown) | Section 6.4.3.3.1 | Program occupied/unoccupied schedules; verify they match actual occupancy |
| Setback controls | Section 6.4.3.3.2 | Configure unoccupied heating and cooling setpoints per the standard (see below) |
| Optimum start | Section 6.4.3.3.3 | Enable optimum start on systems with setback controls and DDC |
| Zone isolation | Section 6.4.3.3.4 | Verify isolation zones (each floor, maximum 25,000 ft²) can be scheduled separately |
| Demand-controlled ventilation | Section 6.4.3.8 | Install and program DCV for qualifying spaces |
| DDC requirements | Section 6.4.3.10 | Confirm DDC coverage and required reset/alarm capabilities |
| Economizer fault detection and diagnostics | Section 6.4.3.12 | Confirm required FDD status points and fault displays on qualifying air-cooled DX units |
| VAV static pressure setpoint reset | Section 6.5.3.2.3 | Reset duct static pressure based on the zone requiring the most pressure |
| Supply air temperature reset | Section 6.5.3.5 | Reset multiple-zone supply air temperature based on building loads or outdoor air temperature |
The standard's controls requirements generally use the phrase "capable of and configured to," which means the controller must actually be programmed to perform the function, not merely able to.
Setback Requirements
Section 6.4.3.3.2 (as revised by Addendum bk to 90.1-2019) requires heating systems to be capable of and configured to automatically restart and temporarily operate as needed to keep zone temperatures above an adjustable heating setpoint at least 10°F below the occupied heating setpoint. Cooling systems must be capable of and configured to maintain zones below an adjustable cooling setpoint at least 5°F above the occupied cooling setpoint, or to prevent high space humidity levels as required by Standard 62.1. DOE's 90.1-2019 training notes an exception for radiant heating systems with a setback setpoint at least 4°F below the occupied heating setpoint.
Section 6.4.3.3 exempts HVAC systems with heating and cooling capacity under 15,000 Btu/h and systems intended to operate continuously from the off-hour control requirements.
Leaving systems at occupied setpoints around the clock defeats the purpose of these requirements and wastes energy.
Optimum Start Requirements
Section 6.4.3.3.3 requires optimum start controls on individual heating and cooling air distribution systems that have setback controls and DDC. At a minimum, the control algorithm must be a function of the difference between space temperature and the occupied setpoint, the outdoor temperature, and the amount of time before scheduled occupancy. Mass radiant floor slab systems must also include floor temperature in the algorithm.
For facility managers, this means verifying that:
- The DDC system has optimum start enabled and is not overridden to a fixed early-start schedule
- The algorithm is using space temperature, outdoor air temperature, and time to occupancy as inputs
- The pre-conditioning window is being minimized, not padded for comfort margin
ASHRAE Guideline 36: High-Performance Sequences of Operation
What Guideline 36 Is -- and What It Isn't
ASHRAE Guideline 36-2024, High-Performance Sequences of Operation for HVAC Systems, provides standardized, detailed control sequences for common commercial HVAC systems, along with functional tests to confirm the sequences are implemented. The guideline was first released in 2018 and has been updated since, with the 2024 edition as the current version.
As a guideline, it is not enforceable on its own. It becomes a requirement when a code or a project specification references it. The most significant example is California's 2025 Title 24, Part 6, discussed below.
What Guideline 36 Covers
Guideline 36 covers sequences for common air-side and plant systems, including VAV terminal units, multiple-zone and single-zone VAV air-handling units, and central plant equipment. Key sequence elements include:
- Supply air temperature reset based on zone demand
- Duct static pressure reset using trim-and-respond logic
- Minimum outdoor air control and DCV integration
- Economizer control
- Zone-level airflow and heating/cooling control for terminal units
- Automated fault detection and diagnostics (AFDD)
Consult the guideline itself for the exact system types and section structure in the edition you are using.
The Energy Case for Guideline 36
Reported savings vary by building and baseline. An ASHRAE Manitoba chapter presentation on Guideline 36-2024 cites energy savings of 10 to 30 percent achieved mainly through improved control logic, and references a Lawrence Berkeley National Laboratory analysis that estimated average savings of 31 percent for multiple-zone air-handler systems in a medium commercial building. The savings come mainly from supply air temperature reset, duct static pressure reset, and optimized ventilation control.
The performance gains come from integrated logic across operating modes, not individual features in isolation. A building with piecemeal BAS programming may implement individual features correctly while still operating inefficiently because those features are not coordinated.
Fault Detection and Diagnostics in Guideline 36
One of Guideline 36's distinctive contributions is automated fault detection and diagnostics built into the sequences. AFDD logic evaluates operating conditions and alerts operators to problems -- for example, supply air temperature that cannot be maintained, economizer or damper problems, or simultaneous heating and cooling -- before they cause major performance issues.
This matters for compliance because it creates an audit trail. When a commissioning provider or energy auditor reviews BAS data, a system with working AFDD shows either evidence of correct operation or a documented fault history that explains deviations.
Demand-Controlled Ventilation: Compliance Details
When DCV Is Required Under ASHRAE 90.1
The trigger for DCV depends on which edition of 90.1 applies.
Under 90.1-2019, Section 6.4.3.8 requires DCV for each space larger than 500 ft² with a design occupancy for ventilation of more than 25 people per 1,000 ft², where the HVAC system has at least one of the following: an air-side economizer, automatic modulating control of the outdoor air dampers, or design outdoor airflow greater than 3,000 cfm. Exceptions include systems with exhaust air energy recovery meeting Section 6.5.6.1, multiple-zone systems without DDC of individual zones communicating with a central control panel, systems with design outdoor airflow under 750 cfm, spaces where more than 75 percent of the outdoor air is makeup or transfer air for exhaust, and certain occupancy categories (correctional cells, daycare sickrooms, science labs, barber/beauty/nail salons, and bowling alley seating).
Addendum b to 90.1-2019 (approved in 2021) replaced the single 500 ft²/25-people threshold with a table (Table 6.4.3.8) that sets floor-area thresholds by climate zone and by the occupant outdoor airflow component per 1,000 ft² from Standard 62.1. It removed the exhaust energy recovery and under-750-cfm exceptions (accounting for them in the table instead) and added an exception for spaces where Standard 170, other codes, or accreditation standards do not allow outdoor air to be reduced. If you are on a later edition, use the table in your adopted version.
Spaces that commonly trigger DCV include conference rooms, classrooms, lecture halls, theaters and assembly spaces, and some retail and lobby spaces.
CO2 Sensor Requirements
CO2 sensing is the most common way to implement DCV. According to a summary of ASHRAE 62.1-2022 published by sensor maker Kaiterra, Standard 62.1 requires CO2 sensors used for DCV to be:
- Accurate to within ±75 ppm at both 600 ppm and 1,000 ppm
- Factory-calibrated, and not require calibration more often than every five years
- Paired with a failure response that resets the ventilation system to supply the required minimum outdoor air when a sensor failure is detected
Place sensors where they represent the occupied zone, away from supply diffusers, exhaust grilles, and doorways, and verify that the DDC system actually responds to readings by modulating outdoor air dampers, adjusting VAV minimums, or both.
No Universal CO2 Setpoint
There is no single code-mandated CO2 setpoint for DCV. Control setpoints depend on the space type, the ventilation rate procedure used, and outdoor CO2 levels. Have the design engineer document the basis for each DCV setpoint.
Common DCV Compliance Failures
Facility managers conducting internal audits or preparing for commissioning reviews should verify that DCV systems are not subject to these common failures:
Sensors bypassed or points not enabled in BAS. CO2 sensors are often installed during construction but never wired into the DDC logic or are placed in manual override. Physical installation does not equal functional compliance.
DCV disabled during occupied schedules. Some programming defaults lock the outdoor air damper at design minimum during occupied hours regardless of CO2 readings. This disables the DCV function entirely.
No low-limit on outdoor air. DCV systems must still provide the minimum ventilation required by ASHRAE 62.1 or the mechanical code even when CO2 readings are low. A DCV sequence that allows outdoor air to drop to zero is not compliant.
Setpoints without a documented basis. Using a generic CO2 setpoint that has not been evaluated for the specific space is a common weakness.
Economizer Controls: Section 6.5.1 Requirements
Airside Economizer Requirements
ASHRAE 90.1 Section 6.5.1 requires economizers on cooling systems based on climate zone and system size (Tables 6.5.1-1 and 6.5.1-2 in 90.1-2019), with numerous exceptions and an economizer trade-off option for unitary systems that meet higher efficiency levels. Air economizers must be capable of providing up to 100 percent of the design supply air as outdoor air for cooling.
The control sequence must:
- Sequence economizer operation with mechanical cooling
- Provide a high-limit shutoff that automatically reduces outdoor air intake to the minimum outdoor air quantity when outdoor air will no longer reduce cooling energy use
- Use dampers meeting the standard's leakage requirements
- Provide a means to relieve excess outdoor air during economizer operation to prevent building over-pressurization
Economizer High-Limit Controls
The permitted high-limit shutoff control types and their settings by climate zone are listed in Table 6.5.1.1.3 of 90.1-2019. DOE's training summarizes the permitted and prohibited types:
| High-Limit Control Type | Status Under 90.1-2019 | BAS Implementation Notes |
|---|---|---|
| Fixed dry-bulb temperature | Allowed (settings vary by climate zone per Table 6.5.1.1.3) | Program the shutoff setpoint required for your climate zone |
| Differential dry-bulb temperature | Allowed in the climate zones listed in Table 6.5.1.1.3 | Requires outdoor and return air temperature sensors |
| Fixed or differential enthalpy | Allowed only in combination with a dry-bulb high limit | Requires enthalpy (or temperature and humidity) sensing plus a dry-bulb limit |
| Electronic hybrid enthalpy | Not allowed | Replace legacy controls during retrofits |
| Dew point and dry-bulb | Not allowed | Replace legacy controls during retrofits |
Economizer faults -- dampers stuck open or closed, sensor failures, and logic overrides -- are common findings in retrocommissioning. Section 6.4.3.12 requires economizer fault detection and diagnostics on qualifying air-cooled DX units, including fault displays for conditions such as not economizing when it should, economizing when it should not, damper not modulating, and excess outdoor air.
Energy Monitoring Requirements: Section 8 Mandates
Metering Thresholds and Required Endpoints
ASHRAE 90.1 Section 8.4.3 requires measurement devices in new buildings to monitor electrical energy use separately for:
- Total electrical energy
- HVAC systems
- Interior lighting
- Exterior lighting
- Receptacle circuits
As the requirement appeared when it was introduced in 90.1-2013, buildings with tenants must monitor these categories for the total building and, excluding shared systems, for each individual tenant. Up to 10 percent of the load in each end-use category may come from other loads. Usage must be recorded at least every 15 minutes and reported at least hourly, daily, monthly, and annually; each tenant's data must be made available to that tenant; and the system must be capable of maintaining at least 36 months of data. Exceptions include buildings under 25,000 ft², individual tenant spaces under 10,000 ft², dwelling units, residential buildings with less than 10,000 ft² of common area, and critical and equipment branches of NEC Article 517 systems. Section 8.4.3 remains in 90.1-2022; confirm the exact exceptions in your adopted edition.
For facility managers, this means a BAS or metering system with only real-time display does not satisfy the requirement. The system must log interval data and retain it for the required period, either locally or on a data platform.
| Building Characteristic | Monitoring Requirement | Data Retention | Recording Interval |
|---|---|---|---|
| New building 25,000 ft² or larger | Total building plus HVAC, interior lighting, exterior lighting, and receptacle circuits | Capable of 36 months | At least every 15 minutes |
| Tenant space 10,000 ft² or larger (in covered building) | Same categories monitored for the tenant (excluding shared systems) | Capable of 36 months | At least every 15 minutes |
| Buildings under 25,000 ft² | Excepted under 90.1 (state/local codes may still apply) | N/A | N/A |
California Title 24 2025: A Preview of Code Direction
Guideline 36 as an Enforceable Requirement
California's 2025 Building Energy Efficiency Standards (Title 24, Part 6) took effect January 1, 2026. Section 140.4(r) requires HVAC systems with DDC controllers to use programming originating from a programming library based on the sequences of operation in ASHRAE Guideline 36. The programming library must be certified to the California Energy Commission as meeting the requirements of Reference Joint Appendix JA18. According to an engineering firm's overview of the 2025 changes, the Guideline 36-based requirements cover VAV systems, economizers, supply air temperature reset controls, and DDC controller logic, and apply to new or replacement systems.
This is a significant step: it makes the content of the BAS programming -- not just the hardware -- a code compliance element.
Acceptance Testing Requirements
Title 24 requires acceptance testing of nonresidential mechanical systems and controls, performed by certified Acceptance Test Technicians (ATTs), who are trained and certified by Acceptance Test Technician Certification Providers (ATTCPs). The Statewide CASE Team's Guideline 36 proposal for the 2025 code included updates to the acceptance tests to reflect the new programming-library approach. Check the CEC's current compliance documents for the specific tests that apply to your project.
For facility managers in California, this means BAS commissioning is a regulated activity, not just an owner-elected quality assurance measure.
BAS Compliance: A Practical Facility Manager Checklist
Use this framework when conducting an internal BAS compliance review or preparing for a commissioning inspection:
| Compliance Area | Key Verification Points | Standard Reference |
|---|---|---|
| DDC System Coverage | Systems meeting Table 6.4.3.10.1 triggers have DDC installed and active, with required reset and alarm capabilities | ASHRAE 90.1 Section 6.4.3.10 |
| Setback Controls | Occupied/unoccupied schedules programmed; heating setback at least 10°F and cooling setup at least 5°F from occupied setpoints; schedules match actual use | ASHRAE 90.1 Section 6.4.3.3.2 |
| Optimum Start | Enabled; not overridden to a fixed time; using space temperature, outdoor temperature, and time-to-occupancy inputs | ASHRAE 90.1 Section 6.4.3.3.3 |
| Dead Band | At least 5°F dead band where required; simultaneous heating and cooling prevented | ASHRAE 90.1 Section 6.4.3.1 |
| Demand-Controlled Ventilation | CO2 sensors installed, wired, and active in DDC logic; DCV not bypassed; minimum ventilation maintained | ASHRAE 90.1 Section 6.4.3.8 |
| Economizer Controls | Dampers modulate correctly; high-limit type and setting match climate zone; not locked in override; FDD active where required | ASHRAE 90.1 Sections 6.5.1 and 6.4.3.12 |
| Supply Air Temp Reset | Reset logic active and tied to building loads or outdoor air temperature; not locked at design SAT year-round | ASHRAE 90.1 Section 6.5.3.5 |
| Duct Static Pressure Reset | VAV static pressure setpoint resets based on the zone requiring the most pressure; not fixed at design pressure | ASHRAE 90.1 Section 6.5.3.2.3 / Guideline 36 |
| Energy Metering | Covered buildings have end-use monitoring; 15-minute interval data being logged; 36-month storage confirmed | ASHRAE 90.1 Section 8.4.3 |
| Guideline 36 Programming (CA) | DDC programming originates from a CEC-certified Guideline 36 programming library; acceptance test documentation on file | Title 24 2025 Section 140.4(r) / JA18 |
Common Compliance Gaps and How to Address Them
The most frequently encountered BAS deficiencies in commercial buildings fall into three categories:
Programming overrides that have never been removed. During construction or initial occupancy, contractors and commissioning agents routinely place systems in override to facilitate testing or occupant comfort. These overrides -- locked damper positions, disabled optimum start, bypassed DCV, fixed setpoints -- are often never removed. A systematic review of all BAS points for active overrides is one of the highest-value actions a facility manager can take.
Sensor failures creating invisible non-compliance. A failed CO2 sensor may leave outdoor air at the wrong rate. A stuck economizer damper or failed temperature sensor may prevent free cooling even when conditions favor it. Because these failures may not trigger alarms on systems without FDD, they can persist for years. Periodic sensor verification should be a standard maintenance task.
Energy metering gaps after renovation or expansion. Buildings constructed before metering requirements applied, or expanded later, may lack the monitoring infrastructure that current codes expect for new construction. Reviewing metering requirements as part of building expansions or major HVAC replacements helps avoid surprises at permit inspection.
Sources and References
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ANSI/ASHRAE/IES Standard 90.1-2019: HVAC (training presentation, PNNL-SA-153210). U.S. DOE Building Energy Codes Program / Pacific Northwest National Laboratory, hosted by Oregon Building Codes Division. https://www.oregon.gov/bcd/codes-stand/Documents/90.1-2019-HVAC-training.pdf
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Addendum bk to ANSI/ASHRAE/IES Standard 90.1-2019 (setback controls). ASHRAE. https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/90_1_2019_bk_20220121.pdf
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Addendum b to ANSI/ASHRAE/IES Standard 90.1-2019 (demand control ventilation). ASHRAE. https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/90_1_2019_b_20210401.pdf
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6.4.3.10 Direct Digital Control (DDC) Requirements (NYC Energy Code 2025). UpCodes. https://up.codes/s/direct-digital-control-ddc-requirements
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ASHRAE 90.1-2013 Chapter 8 Electrical Energy Monitoring (Section 8.4.3 excerpt). EZ Meter. https://ezmeter.com/wp-content/uploads/2022/07/ASHRAE-Chapter-8-Electric-Submeter-Specific-Regulations.pdf
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ASHRAE 90.1's Requirements for Electrical Monitoring. Utilivisor. https://www.utilivisor.com/news/ashrae-90-1.html
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ASHRAE Guideline 36-2024: Introduction and Use Cases. ASHRAE Manitoba Chapter. https://www.ashraemanitoba.ca/wp-content/uploads/4.-ASHRAE-Guideline-36-2024.pdf
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Ensuring ASHRAE 62.1 Compliance for CO2 Sensors in Demand-Controlled Ventilation. Kaiterra. https://learn.kaiterra.com/en/resources/ensuring-ashrae-62.1-compliance-for-co2-sensors-in-demand-controlled-ventilation-dcv
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Appendix JA18 -- Guideline 36 Programming Library Requirements. Energy Code Ace. https://energycodeace.com/content/cy25-appendix-ja18-guideline-36-programming-library-requirements
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Manufacturer Certification for Building Equipment (Guideline 36 programming library). California Energy Commission. https://www.energy.ca.gov/rules-and-regulations/building-energy-efficiency/manufacturer-certification-building-equipment-0
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Overview of 2025 Title 24, Part 6 Changes. Schnackel Engineers. https://schnackel.com/blogs/overview-of-2025-title-24part-6-changes
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Nonresidential HVAC Controls -- ASHRAE Guideline 36 CASE Report. California Statewide Codes and Standards Enhancement Team. https://title24stakeholders.com/wp-content/uploads/2023/08/2025_T24_CASE-Report-Final_NR-HVAC-Guideline-36.pdf
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California's Energy Code Update Guides the Construction of Cleaner, Healthier Buildings. California Energy Commission News. https://www.energy.ca.gov/news/2026-01/californias-energy-code-update-guides-construction-cleaner-healthier-buildings
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Understanding ASHRAE 90.1's Role in Energy Codes and Regulations. Consulting-Specifying Engineer. https://www.csemag.com/understanding-ashrae-90-1s-role-in-energy-codes-and-regulations/
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ASHRAE Standard 90.1. ASHRAE Bookstore. https://www.ashrae.org/technical-resources/bookstore/standard-90-1
