An HVAC installation does not save energy simply because it has a new controller or an elaborate BMS dashboard. Savings arise when heating, ventilation and cooling deliver the conditions actually required by building occupants or the process. In practice, it is therefore worth starting an upgrade with schedules, sensors and control sequences rather than choosing a new platform.
A sound project combines three objectives: lower energy consumption, continued compliance with operating requirements, and the ability to verify results using data. Below, we examine where the greatest potential is commonly found and how to define a scope of work that can be verified at handover.
HVAC controls at a glance: where should you start?
- Compare system operation with actual building use. Check the operating hours of air-handling units, pumps, chillers and heat sources.
- Verify setpoints and equipment coordination. Simultaneous heating and cooling or unnecessarily high available pressure can waste energy.
- Adjust flow rates only within operating requirements. Minimum ventilation rates, hygiene, safety and process conditions take precedence over energy savings.
- Record trends before and after the upgrade. A BMS screenshot alone is not sufficient evidence of energy savings.
- Commission the functions, not just the installation. Test normal operation, extreme conditions, sensor failure and the return to a safe operating mode.
What do HVAC controls cover, and where is energy wasted?
HVAC controls comprise parameter measurement, the operation of actuators and the logic that determines how a system runs. They can include air-handling unit controllers, variable-flow systems, fan and pump variable-frequency drives, control valves, frost protection and the control of heating or cooling sources. A building management system (BMS) can integrate these functions, but a BMS is not essential for every control function.
It is important to distinguish operational energy waste from design-related problems. An air-handling unit running at night in an empty office building may only need a schedule adjustment. By contrast, programming alone will not make a system efficient if the ducts are undersized or the pump is incorrectly specified.
| Area | Typical sign of a problem | Possible control function | Checks before making a change |
|---|---|---|---|
| Operating schedules | Running at full capacity outside occupied hours | Calendars, operating modes, optimum start and stop | Actual occupancy, start-up requirements, round-the-clock needs |
| Heating and cooling | Heating and cooling valves opening simultaneously | Deadband, priorities and sequence interlocks | Sensor accuracy, humidity, process requirements |
| Fans and pumps | Constant high flow despite variable demand | Speed control and pressure setpoints | Minimum flow, system characteristics, pressure losses |
| Outdoor air | A single setpoint regardless of zone occupancy | Demand-controlled ventilation | Minimum airflow, pollutant sources, sensor quality |
| Heating and cooling sources | Unnecessary start-up of additional units | Staging, priorities and supply temperature reset | Part-load efficiency, minimum run time |
U.S. Department of Energy guidance on building operations and maintenance discusses diagnosing and fine-tuning existing installations as a way to improve their performance. Before purchasing new equipment, it is therefore worth establishing whether excessive energy use results from scheduling, setpoints, faulty control or a design issue. This does not guarantee any particular percentage of savings.
Which data and signals should drive the system?
HVAC control should be based on parameters that genuinely reflect demand. Measuring the outdoor temperature and sending alarms to an operator is not enough. You need to understand how quickly the system responds to setpoint changes, which loads take priority and what should happen if a signal is lost.
| Data group | Example data points | Role in decision-making |
|---|---|---|
| Occupancy and operating conditions | Temperature, humidity, CO₂ concentration where representative, zone occupancy | Confirming demand and maintaining required conditions |
| Flow and resistance | Air or water flow, static and differential pressure, damper and valve positions | Controlling fans, pumps and distribution of the medium |
| Sources and loads | Supply/return temperatures, equipment status, load, demand signals | Selecting operating sequences and balancing demand |
| Energy and time | Electrical power, energy use, heating/cooling consumption, schedules, manual/automatic mode | Identifying unnecessary operation and evaluating results |
| Safety | Frost protection temperature, pressure switches, interlocks, fire-safety and fault signals | Forcing a safe state regardless of optimisation |
The points list should distinguish setpoint, actual value, command signal and status feedback. For example, a command to open a damper does not prove that it has opened. Likewise, a frequency reading from a variable-frequency drive is not the same as a flow or power measurement.
Data quality matters more than the number of charts. Before modifying control sequences, identify out-of-calibration sensors, substituted signals, persistent manual overrides, incorrect timestamps and gaps in trend logs. Otherwise, the system may execute the wrong algorithm with great precision.
Schedules and setpoints: usually the first things to check
Air-handling units and pumps often still follow schedules set several years ago, even though production hours, tenants or building use have changed. Compare the weekly power profile with shift rosters and note any manual extensions of operating hours. Only then determine which loads can switch to setback mode and which must run continuously.
Avoiding simultaneous heating and cooling
With two control loops set to almost the same temperature, one valve may heat the air while another cools it. Causes can include an overly narrow deadband, an illogical sequence, a poorly located sensor or a dehumidification requirement. Any change should therefore involve reviewing the deadband, hysteresis, priorities and changeover conditions, not simply increasing the setpoint difference arbitrarily.
If dehumidification requires cooling followed by reheating, the presence of both processes does not in itself indicate a fault. First verify the required humidity level and available control methods.
Start-up, night setback and process constraints
Optimum start means switching the system on early enough to meet the required conditions when occupancy begins, but no earlier than necessary. Night setback must not cause excessive cooling of the installation, breaches of storage requirements, condensation or loss of the required air-change rate. Schedules should therefore be approved with building users and the people responsible for process operations and safety.
Demand-controlled ventilation: when does it make sense?
Demand-controlled ventilation (DCV) adjusts outdoor airflow to changing demand, such as the number of occupants. In suitably designed systems, the total supply airflow may also vary. Where ventilation load is mainly driven by occupancy, CO₂ measurements or zone occupancy data can be useful. However, this is not a universal control strategy for industrial ventilation.
Where a facility emits dust, solvents or process heat, or must maintain negative pressure, extraction may be necessary regardless of occupancy. CO₂ does not measure every pollutant and cannot replace an airflow balance or safety requirements. Minimum flow rates, supply and extract airflow, flow directions and agreed emergency scenarios must be defined before DCV is commissioned. ASHRAE describes this control approach in its chapter on control system design.
Why can reducing airflow produce significant fan-power savings?
At a comparable operating point in a system dominated by frictional resistance, fan power varies approximately with the cube of speed. In this model, reducing speed to 80% of its original value gives a power ratio of 0.8 × 0.8 × 0.8 = 0.512, or approximately 49% lower instantaneous power.
This does not mean a 49% reduction in annual energy use. Actual results depend on system resistance, required pressure, fan and drive efficiency, available speed-control range and operating hours at different loads. If consistently high flow rates are required, the scope for reducing power may be limited. Verification should use electrical data and flow measurements, not drive frequency alone.
Coordinating air-handling units, pumps and heating or cooling sources
An upgrade should cover the sequence of the entire system, rather than independent settings for each device. An air-handling unit may call for heat, but the source should establish whether there is actual demand and whether hydraulic flow meets requirements. Similarly, a cooling demand signal should be linked to chiller staging and pump control.
- Supply temperature reset: adjusting the setpoint to outdoor conditions or load requirements can reduce avoidable losses, provided the necessary parameters and heat-source efficiency are maintained.
- Pressure control: a permanently high setpoint can lead to throttling at valves and dampers. For controlled systems, consider adjusting pressure based on end-device positions or zone demand.
- Source staging: control logic must account for minimum output, run and stop times, defrost cycles and manufacturers’ limitations.
- Heat recovery: heat exchanger bypass, frost protection and recovery operation should follow the temperature and humidity balance, not a single fixed threshold.
For questions about selecting and applying energy recovery solutions, a separate reference is industrial heat recovery. Here, the focus is on controlling existing components rather than designing an entire heat-recovery installation.
In production-related systems, process requirements also take priority: specified temperatures, humidity, positive or negative pressure, and acceptable recovery time following a failure. Before changing the control logic, establish which parameters are non-negotiable and which merely reflect established operating practice.
HVAC controls, BMS and energy management: what is the difference?
A local controller performs the device’s control functions. A BMS can collect data, transmit setpoints and display alarms. Energy management, however, also involves defining indicators, responsibilities, response procedures and regular performance reviews. Installing a BMS is not the same as implementing an ISO 50001-compliant energy management system.
In practice, information needs to flow in both directions: from control systems into analysis, and from operational decisions back into setpoints. This is what distinguishes an alarm from genuine corrective action. We discuss the process in more detail in our article on energy monitoring in businesses.
Standards and requirements for building automation
The PN-EN ISO 52120-1:2022-09 standard structures the automation and control functions that affect the energy performance of buildings and the methods used to assess their impact. It provides a reference for functional system specifications, not proof that every installation will automatically achieve a particular level of savings.
Polish regulations applicable to certain non-residential buildings required building automation and control systems to be installed by 31 December 2024 where the combined nominal heating output of the relevant heating system (or combined heating and ventilation system), or the combined nominal cooling capacity of the relevant air-conditioning system (or combined air-conditioning and ventilation system), exceeds 290 kW — provided the measure is technically and economically justified. Article 3 of the Polish Act of 7 October 2022 sets out, among other matters, how technical feasibility and economic viability are assessed (an investment payback period of no more than 5 years).
In turn, Directive (EU) 2024/1275, Article 13(9), provides for the relevant non-residential buildings to be covered by a threshold of over 70 kW by 31 December 2029, subject to feasibility conditions. This is an EU requirement whose application to a particular property must be assessed alongside current national law and its transposition. Thresholds for technical building systems should not automatically be applied to every industrial process installation.
How to plan an HVAC controls upgrade step by step
- Describe the system and operating objectives. Define system boundaries, zones, occupancy schedules, required temperatures, humidity, flow rates and critical safety requirements.
- Assess the existing installation. Collect control diagrams, the points list, setpoints, equipment manuals, available trend logs and the fault history. Perform spot checks of sensor readings and actuators.
- Distinguish measures requiring no investment from investment measures. Separate calendar and sequence adjustments from the need for new transmitters, drives, valves or communications integration.
- Specify control sequences unambiguously. For each mode, define entry and exit conditions, setpoints, priorities, limits and fault responses. Agree who is authorised to make permanent setpoint changes.
- Define acceptance criteria before implementation. Assign a test scenario, expected response, logged data points and acceptance criteria to each function.
- Plan post-commissioning monitoring. A one-day acceptance test cannot cover every season. Keep a list of functions to verify in winter, summer and under changing loads.
Replacing the entire system is not always necessary. If the controllers are functional, handle the required signals and allow sequences to be modified safely, phased optimisation may be more sensible than a complete migration. If documentation, program access or spare parts are unavailable, assess the risks of retaining the existing system separately.
Which functional tests and trends belong in acceptance testing?
An acceptance report should not stop at stating that every point on the graphical display is green. U.S. Department of Energy guidance on HVAC commissioning emphasises verifying system performance against design requirements, including in existing buildings.
| Test scenario | What should be confirmed | Acceptance evidence |
|---|---|---|
| Day/night changeover | Mode changes at the scheduled time without breaching constraints | Trends for air-handling unit status, schedules and temperatures |
| Reduced demand | Reduced flow and power while maintaining minimum requirements | Flow, pressure, electrical power, damper positions |
| Heating and cooling | No unjustified opposing operation; stable control | Temperatures, valve signals, modes and alarms |
| Sensor fault or signal loss | Alarm, emergency response and prescribed safe operating mode | Fault simulation report, alarm and recovery records |
| Restart after power loss | Correct start-up sequence and functioning interlocks | Event log and equipment start-up sequence record |
| Process requirements | Process conditions maintained as loads change | Trends for temperature, humidity and required process parameters |
Trend logging frequency must match the dynamics of the system. Hourly data may be sufficient for a preliminary review of schedules but will not capture brief valve oscillations or start-up sequences. Retain the program version, setpoint list, test descriptions and the identity of the person approving the change.
How can you verify that HVAC controls actually saved energy?
A change in energy consumption after an upgrade does not in itself prove savings. Compare periods with similar occupancy, load, weather and operating requirements, or use a model that accounts for their differences. Useful measurements include electricity consumption by fans and pumps, heating and cooling energy, as well as flow, temperature and operating hours. U.S. DOE guidance on measuring and verifying energy savings explains how to establish a baseline and verify results.
Illustrative example: a change in average fan power
Suppose a fan previously drew an average of 12 kW for 3,000 hours a year. After a change to the controls, average power consumption during comparable operating hours and under comparable conditions is 9 kW. The calculation is as follows:
- Before the change: 12 kW × 3,000 h = 36,000 kWh.
- After the change: 9 kW × 3,000 h = 27,000 kWh.
- Difference: 9,000 kWh, or 9 MWh over the period assumed.
This example illustrates the method, not the outcome of a specific project. Such a comparison requires confirmation that both average power figures reflect comparable loads and that neither the required airflow nor zone conditions have deteriorated. It is also necessary to check whether the change in fan operation increased consumption by heating, cooling or other equipment. Financial benefits can only be calculated after applying the relevant energy tariff and considering the effect on other billing components.
The most useful performance indicator depends on the function of the installation. For some facilities it will be kWh per occupied hour; for others, energy use adjusted for outdoor temperature, airflow or production volume. Changing settings without documenting the baseline and comparison conditions makes subsequent investment appraisal more difficult.
What should you prepare before discussing an upgrade?
A full measurement campaign is usually not necessary for an initial assessment. The most useful materials are:
- control diagrams and process or installation schematics;
- an up-to-date points list identifying measured values, setpoints and control signals;
- operating schedules, setpoints and descriptions of automatic and manual modes;
- available trends for temperatures, flows, pressures, power and equipment status;
- a description of required building or process parameters and safety constraints;
- details of known problems: overheating, insufficient cooling, oscillations, alarms and manual overrides.
This information helps establish whether fine-tuning is sufficient, a control-loop diagnosis is needed or a broader technical intervention is required. The wider context of improving energy efficiency in a business can also help prioritise upgrades, but HVAC controls should have their own requirements and savings measurement plan.
Conclusion: upgrade operating logic, not just the control cabinet
A major mistake is to treat the number of new sensors, screens and BMS points as a measure of project success. What matters is whether the installation eliminates unnecessary operation, responds to load, maintains required conditions and allows its performance to be verified. Start with data, sound control sequences and functional testing, then decide how extensive the upgrade needs to be.
If you are planning changes to HVAC controls, describe the current problem and email audytor@energytrend.pl with any available control diagram, points list, schedules and several representative trend logs. Energy Trend can use these to help define the scope of an initial diagnostic assessment and the next analytical steps. A complete set of measurements is not required at this stage.
Sources and reference documents
- U.S. Department of Energy – technical systems operations and maintenance.
- U.S. Department of Energy – HVAC commissioning.
- ASHRAE Handbook – control system design and application (2019 edition).
- PKN – PN-EN ISO 52120-1:2022-09.
- Polish Ministry of Development and Technology – building automation and control systems.
- Sejm of the Republic of Poland – Article 3 of the Act of 7 October 2022 (text published in Journal of Laws 2024, item 101).
- EUR-Lex – Directive (EU) 2024/1275.
- U.S. Department of Energy – measurement and verification of savings.
