Reduce Commercial HVAC Energy Use: 10 BAS Checks

Commercial HVAC energy projects often begin with a capital question: Which chiller, rooftop unit, boiler, or control system should we replace?

That can be the right question, but it should not be the first one. A well-designed building can still waste energy when schedules drift, sensors read incorrectly, equipment runs outside occupied hours, control loops fight each other, or reset strategies are disabled.

The U.S. Department of Energy (DOE) points to building controls as a major efficiency opportunity and notes that successful high-performance controls implementations have demonstrated substantial HVAC energy reductions. ENERGY STAR also recommends starting with operations and maintenance measures, especially scheduling, calibration, and better use of existing energy-management systems.

Quick Answer

Before buying new HVAC equipment, review these ten areas:

Operating schedules and after-hours overrides
Heating and cooling setpoints and deadbands
Simultaneous heating and cooling
Supply-air and water-temperature reset strategies
Static-pressure and differential-pressure reset
Economizer and outdoor-air control
VFD operation and minimum-speed settings
Sensor accuracy and BAS point quality
Equipment staging and lead/lag logic
BAS trends, alarms, and measured energy data

1. Start With Schedules

One of the simplest ways to waste HVAC energy is to run equipment when the building does not need it. ENERGY STAR specifically identifies scheduling as a high-value O&M measure because overrides and special-event schedules can remain active long after the original need has passed.

Check AHUs, RTUs, pumps, exhaust fans, boilers, chillers, and terminal equipment against actual occupancy. Look beyond the local schedule if the BAS has multiple supervisory levels.

Field Lesson: The Local Schedule Was Not the Final Command

At one commercial building, a fan schedule issue was investigated at the server, JACE, and Smart Building levels. The local schedule appeared correct, but a higher-level Smart Building JACE was overriding it. The supervisory logic was corrected so the intended local schedule could operate.

No measured energy savings were recorded for that service call, so it would be wrong to attach a savings percentage to the fix. The operational lesson is still valuable: a schedule that looks correct on one graphic may not be the schedule that owns the final command.

2. Review Setpoints and Deadbands

A building can waste energy when heating and cooling setpoints are too close together, when zones have permanent overrides, or when seasonal setpoints no longer match the sequence of operation.

Do not copy a deadband from another building. Review the site design, comfort requirements, humidity needs, and control sequence. The goal is to prevent unnecessary heating and cooling while maintaining acceptable indoor conditions.

3. Look for Simultaneous Heating and Cooling

Simultaneous heating and cooling can occur when an air handler supplies overly cold air while terminal reheat compensates, when hot- and cold-deck sequences fight each other, or when zone loops are poorly coordinated.

Trend supply-air temperature, cooling-valve position, heating-valve position, reheat demand, and representative zone temperatures. If heating and cooling stay active together for long periods, determine whether the condition is required for humidity or process control or whether it is a controls problem.

4. Use Temperature Reset Instead of One Fixed Setpoint

DOE and modern high-performance control guidance support adjusting HVAC setpoints to actual load rather than holding aggressive design conditions all year. Examples include chilled-water reset, hot-water reset, and supply-air-temperature reset.

Reset strategies must be commissioned carefully. Raising chilled-water temperature may reduce chiller lift but can increase pumping or airside energy if coils and valves can no longer satisfy load. The best setpoint is the one that minimizes total system energy while maintaining the required conditions.

5. Reset Static and Differential Pressure

A VAV supply fan or variable-speed hydronic pump does not always need the same pressure setpoint at every load. ASHRAE Guideline 36 includes demand-based reset concepts intended to reduce unnecessary fan and pump energy while maintaining terminal performance.

Before adding reset logic, make sure the sensors, VAV boxes, valves, and feedback points are reliable. Optimization built on bad inputs usually creates a new troubleshooting problem.

6. Verify Economizer Operation

DOE commissioning guidance specifically calls out outside-air dampers and economizer controls because they can affect both comfort and energy performance.

Check whether the economizer is enabled under appropriate outdoor conditions, whether the damper actually follows its command, and whether mechanical cooling stages coordinate correctly with free cooling. A BAS command does not prove that a damper moved.

7. Check VFD Control – Not Just VFD Presence

Installing a VFD does not automatically make a system efficient. A fan or pump that sits at 100% because of an override, incorrect minimum speed, bad pressure sensor, or poor sequence can consume energy as if the drive were not being used effectively.

Trend speed command, actual speed, controlled variable, and setpoint together. The objective is to verify that the equipment slows down when system demand falls.

8. Verify Sensors Before Optimizing

Controls can only make good decisions from good data. Temperature, pressure, humidity, CO2, airflow, and occupancy sensors should be checked when their readings drive major energy decisions.

A small sensor error can influence thousands of hours of operation. Compare critical BAS values with field measurements before changing the sequence around them.

9. Review Staging and Lead/Lag Logic

Equipment that stages too early, runs unnecessary standby capacity, or fails to rotate properly can increase runtime and reduce reliability. Chillers, boilers, pumps, and cooling towers should be sequenced according to the actual plant design and load.

Do not optimize staging only for one component. Turning on a second chiller may reduce individual compressor loading while increasing pump and tower energy. Evaluate the plant as a system.

10. Measure Before and After

Energy optimization without a baseline becomes guesswork. Use utility data, interval meters, BAS trends, runtime, weather-normalized analysis where appropriate, or an energy-management information system to establish what changed.

If a controls change improves comfort but increases energy use, that tradeoff should be visible. If an energy project claims savings, the operating data should support the claim.

An Anonymized Field Case: A Zero-Percent Command That Did Not Close the Valve

At one commercial air-handling system, a cooling-valve actuator modulated but did not appear to close fully when the BAS command reached 0%. The graphic alone could not show whether the remaining cooling came from a leaking valve, a linkage problem, a failed actuator, or an incorrect output signal.

The diagnostic check compared the BAS command, the controller’s analog-output configuration, and the actuator’s required input range. The installed actuator required a 0–10 VDC signal, while the BAS output had been configured for 2–10 VDC. That mismatch meant the command percentage and the voltage presented to the actuator did not represent the same operating range. The BAS parameter was corrected to 0–10 VDC, and actuator operation was tested afterward.

The energy lesson is broader than this one valve. A 0% graphic command is not proof that a valve or damper is physically closed. Before calculating savings, verify the device signal range from the label or approved documentation, measure the output safely when required, and compare command with mechanical response. Trend valve command, supply-air temperature, relevant heating or cooling stages, and fan status before and after the correction. See 0–10 V vs 2–10 V Actuator Control for the full diagnostic sequence.

What Facility Managers Can Do This Week

Review occupied/unoccupied schedules for major HVAC equipment
Search for permanent or long-duration overrides
Trend one AHU fan speed against static pressure and setpoint
Trend one hydronic pump speed against differential pressure
Compare at least one critical temperature sensor with a field measurement
Review economizer command and feedback on one representative unit
Look for heating and cooling active at the same time

Key Takeaways

Start with operation before capital replacement.
Scheduling and controls can waste energy even when equipment is mechanically healthy.
Reset strategies should respond to real demand, not copied rules of thumb.
Optimization requires trustworthy sensors and feedback.
Measure results instead of assuming a controls change saved energy.

FAQ

Can BAS controls really reduce HVAC energy use?

Yes, but savings vary widely by building and starting condition. DOE reports strong savings potential from properly implemented high-performance controls; that should not be treated as a guaranteed percentage for an individual site.

What is the fastest HVAC energy check?

Schedules and overrides are often a good first place to look because they can create unnecessary runtime without any equipment failure.

Should I lower every VFD speed to save energy?

No. Fan and pump speeds must still satisfy airflow, pressure, temperature, ventilation, and equipment requirements. Use the approved sequence and measured system response.

Do I need new controls to save energy?

Not always. Existing BAS platforms may already support better scheduling, resets, trending, and alarms. Commission and use the capabilities you already have before assuming a full controls replacement is required.

Sources & Further Reading

Disclaimer: This article provides general commercial HVAC and building-automation information. Always follow manufacturer documentation, site-specific procedures, applicable codes, licensing rules, and safety requirements.

How to Reduce HVAC Energy Use in Commercial Buildings: 10 BAS and Operations Checks Before Buying New Equipment