If you manage a commercial building, you’ve probably heard complaints like, “It’s freezing in here,” or “Why is it so hot this afternoon?”
You check the thermostat. It hasn’t changed. It’s set exactly where it should be.
So why does the temperature keep moving up and down?
At Harold Brothers Mechanical, we’ve worked with commercial building owners and facility managers who face this exact frustration. In most commercial buildings, temperature swings occur because the HVAC system responds to changing conditions inside and outside the building, not because the thermostat is set incorrectly.
In this article, you’ll learn why these swings happen, what causes them, and what you can do to keep your building comfortable all day.
All of these things change the temperature inside.
For example, offices on the east side may feel cool in the morning but become hot by the afternoon. A meeting room may feel fine until a group gathers inside and turns on electronics.
The thermostat only measures the air around it. It does not know what is happening in every office, hallway, or conference room. Because conditions change throughout the day, the system constantly adjusts. That adjustment can feel like a series of temperature swings.
In many commercial buildings, one thermostat controls a large area. If that thermostat is in a poor location, the entire space can feel uncomfortable.
If it sits near a window, it may read warmer in the afternoon. If it is near a vent, it may cool down faster than the rest of the space. If it is in a hallway instead of a busy office, it may not reflect how occupied spaces actually feel.
When a thermostat does not accurately reflect the building's temperature, employees will notice hot and cold spots throughout the day. The setting may be correct, but the reading may not tell the full story.
Improper zoning often results in daily temperature fluctuations between offices, floors, or departments.
Many commercial buildings use zoning systems. Zoning allows different areas to receive different amounts of heating or cooling.
However, zoning only works well when it is properly designed and maintained.
Over time, problems can develop. Dampers may stop working. Airflow may become unbalanced. Renovations may add walls or close off once open spaces.
When this happens, one zone may get too much air while another gets too little. As the system turns on and off during the day, those differences become more noticeable.
Proper system sizing is essential for steady, consistent comfort in commercial buildings.
Another common cause of temperature swings is oversized HVAC equipment.
If a system is too large for the building, it heats or cools the air very quickly. Then it shuts off before the air has time to circulate fully. A short time later, it turns back on.
This process is called short cycling.
Short cycling creates fast temperature changes. One moment, the air feels cool and strong. The next moment, it feels warm again.
On the other hand, if a system is too small, it may struggle during peak hours. Afternoon heat or high occupancy can push the system past its limits.
Even when the thermostat and equipment are working properly, airflow problems can cause uneven temperatures.
In commercial buildings, ductwork often runs long distances through ceilings or unconditioned spaces. If ducts leak or lose insulation, the air temperature can change before it reaches its destination.
Blocked vents and dirty air filters can also reduce airflow. When air cannot move freely, some areas receive less heating or cooling than others.
As the system cycles during the day, these weak spots become more noticeable.
Outdoor temperature swings directly impact how stable your indoor environment feels.
Commercial buildings are greatly affected by outdoor conditions.
When outdoor temperatures change quickly, the building absorbs and releases heat at different rates. Glass windows, brick walls, and roofing materials all hold heat and release it slowly.
In spring and fall especially, mornings may require heating while afternoons require cooling. If the HVAC system is not properly adjusted, the building may lag behind these changes.
Even though the thermostat stays at the same setting, the load on the building shifts throughout the day.
Larger commercial buildings often rely on a Building Management System (BMS). These systems control temperature schedules and energy-saving settings.
If the schedule is not aligned with actual building use, temperature swings can occur.
For example, the system may reduce cooling in the late afternoon to save energy. If employees are still working, the space may begin to feel warm. The thermostat setting has not changed, but the programmed schedule has.
The first step is a professional HVAC evaluation. A technician can review thermostat placement, inspect zoning components, test airflow, and confirm that the equipment is properly sized.
Air balancing may also be needed. This process adjusts airflow so each zone receives the correct amount of conditioned air. It is especially important after renovations or layout changes.
Upgrading controls can also help. Systems that use multiple sensors across different areas provide a more accurate picture of building conditions.
Finally, regular maintenance keeps the system clean and efficient. Dirty filters, worn parts, and blocked coils all contribute to uneven performance.
Temperature swings in commercial buildings are more than an inconvenience. They can lower employee productivity, increase tenant complaints, and raise energy costs.
When your system constantly turns on and off or struggles to balance airflow, it works harder than it should. Over time, this leads to more repairs and shorter equipment life.
Most importantly, comfort matters. Employees who are too hot or too cold cannot focus on their work.
If temperatures fluctuate throughout your commercial building, the thermostat is rarely the real problem. Most commercial HVAC temperature swings are caused by uneven heating and cooling, airflow restrictions, zoning issues, improper system sizing, or poorly calibrated controls.
At Harold Brothers Mechanical Contractors, we help businesses diagnose and resolve persistent HVAC temperature inconsistencies through testing, balancing, and controls optimization. When your system is properly designed and calibrated, it delivers steady, reliable comfort, not constant adjustments.
Take a look at our article, “Controls Upgrade Options: Standalone Controls vs. BMS Integration.” We break down the differences between standalone building controls and fully integrated Building Management Systems (BMS), so you can better understand which option makes the most sense for your facility and long-term goals.