Make-up air units are essential for replacing air removed by exhaust systems in commercial buildings like restaurants and warehouses, maintaining balanced airflow and safe indoor conditions. When these systems malfunction, they can become a major source of energy waste.
Facility managers may notice symptoms such as rising utility bills, drafts, humidity, or inconsistent temperatures, which often point to ventilation imbalances, airflow restrictions, or outdated equipment. Understanding and correcting the most common make-up air unit problems can help building operators reduce energy waste, protect comfort, and ensure reliable HVAC performance.
Key Takeaways
- Airflow Imbalance: Unbalanced airflow creates negative or positive pressure, leading to uncontrolled infiltration of outdoor air, which forces the HVAC system to consume more energy.
- Dirty Filters: Clogged filters increase resistance, making fans and heating elements run longer and harder, which boosts energy consumption and shortens equipment lifespan.
- Inefficient Heating: Malfunctioning sensors, stuck dampers, or poor controls cause heating components to operate inefficiently, leading to unnecessary and prolonged heating and dramatically higher winter bills.
- Faulty Dampers: Damaged or stuck outdoor air dampers continuously draw in excessive outside air, significantly increasing the load on HVAC systems for both heating and cooling year-round.
- Maintenance & Modernization: Neglecting regular maintenance causes efficiency loss. Older units lack modern features like variable speed fans and energy recovery, making system upgrades a smart investment for long-term cost management.
Improper Air Balance Between Exhaust and Make-Up Air
Make-up air units exist to replace air that is exhausted from the building. When this balance is off, negative or positive pressure develops indoors. Even small pressure differences can create significant energy waste and comfort problems.
For example, when exhaust fans remove more air than the make-up air unit supplies, the building pulls outside air through cracks, doorways, and loading docks. This uncontrolled infiltration introduces hot summer air or cold winter air that must be conditioned.
Common causes of airflow imbalance include:
- improperly sized make-up air units
- changes to exhaust equipment without adjusting supply airflow
- blocked intake dampers or malfunctioning controls
- aging systems that no longer deliver designed airflow
In many cases, facility managers discover these problems after repeated comfort complaints or rising energy bills. Experienced commercial mechanical contractors can evaluate building pressure and rebalance airflow so ventilation systems operate as intended.
Dirty Filters and Restricted Airflow
Airflow restrictions force fans and heating systems to run longer and consume more energy. When filters become clogged, the system must work harder to move the same volume of air.
Restricted airflow leads to several operational problems:
- increased fan energy consumption
- overheating of heating elements or coils
- reduced ventilation performance
- uneven temperature distribution throughout the building
Many commercial buildings overlook make-up air filters, which are often located on rooftops or in separate mechanical rooms. Without routine HVAC maintenance, filters can remain unchanged for too long, restricting airflow. A simple, regular filter replacement schedule reduces energy waste and extends the lifespan of ventilation equipment.
Heating Components Running Longer Than Necessary
During colder months, make-up air units heat incoming outdoor air before it enters the building. If heating components malfunction or operate inefficiently, the system can consume far more energy than expected.
Several conditions commonly drive up heating costs:
- malfunctioning temperature sensors
- stuck dampers allowing excess outdoor air
- worn heating elements or gas burners
- control systems that fail to modulate heating output
In facilities that operate large exhaust systems, the make-up air unit may run continuously. When heating components are not calibrated properly, the system may heat more air than necessary or run at full capacity even during moderate weather.
A qualified commercial hvac company can evaluate burner efficiency, verify temperature control sequences, and adjust airflow settings to prevent unnecessary heating loads.
Faulty Dampers and Outdoor Air Controls
Dampers regulate how much outdoor air enters the make-up air unit. When these components stick, leak, or fail to respond to controls, the system may continuously draw in outdoor air even when ventilation demand is low.
This can cause several energy-related issues:
- excessive heating demand in winter
- increased cooling loads during summer
- humidity fluctuations that strain HVAC systems
- reduced comfort near air supply zones
Dampers are mechanical components exposed to weather, corrosion, and debris, particularly on rooftop units. Over time, hinges, motors, and actuators wear down or fail entirely.
Routine inspection and timely commercial hvac repair help ensure dampers open and close properly. Correctly functioning controls allow the system to introduce only the amount of fresh air required for safe indoor ventilation.
Lack of Preventive Maintenance for Make-Up Air Units
Make-up air systems often operate behind the scenes and receive less attention than primary HVAC equipment. Because they serve ventilation rather than direct comfort conditioning, maintenance may be delayed until problems become obvious.
However, small mechanical issues inside make-up air units can significantly increase energy consumption.
Typical maintenance tasks that improve system efficiency include:
- inspecting and cleaning intake screens and filters
- verifying airflow balance between exhaust and supply systems
- testing damper operation and actuator response
- checking heating components and fuel efficiency
- confirming thermostat and sensor accuracy
Many facility teams rely on an hvac service contract to keep these inspections on schedule. Preventive service helps identify worn components early, restore proper airflow, and maintain energy-efficient system performance.
Aging Equipment and Outdated Ventilation Design
Many commercial buildings still operate make-up air units installed decades ago. These systems were designed when energy costs were lower and ventilation strategies were simpler.
Older units frequently lack features that improve efficiency today, such as:
- variable speed fans that adjust airflow to demand
- advanced temperature and humidity controls
- energy recovery systems that reclaim exhaust heat
- integrated building automation controls
As ventilation needs evolve, outdated equipment may struggle to keep up with current operational demands. This results in longer run times, inefficient heating cycles, and higher overall energy consumption.
Facility managers considering system upgrades often evaluate whether modern make-up air equipment or integrated commercial hvac installation and maintenance solutions could reduce long-term energy costs while improving reliability.
Stabilizing Ventilation and Energy Costs in Commercial Buildings
Make-up air unit problems rarely appear suddenly. In most buildings, small airflow restrictions, control issues, or aging components gradually increase energy consumption over time. When ventilation systems stop performing properly, it becomes harder for the HVAC system to keep temperatures stable.
By identifying airflow imbalances, replacing worn components, and maintaining proper controls, facility managers can significantly reduce energy waste while improving occupant comfort. Preventive inspections also help avoid unexpected downtime during extreme weather conditions when ventilation reliability becomes critical.
FAQs on Make-Up Air Unit Efficiency
What is the most significant energy issue caused by an improper make-up air balance?
An improper balance creates negative or positive pressure inside the building, which pulls in unconditioned outdoor air through every crack and doorway (infiltration). This forces your primary HVAC system to work much harder and consume more energy to heat or cool this uncontrolled air.
How do dirty air filters specifically increase my energy bills?
Clogged filters restrict airflow. This forces the unit’s fans and heating elements to run longer and harder to move the required volume of air. The increased effort and run time boost energy consumption and can shorten the lifespan of the equipment.
Why do faulty dampers lead to high energy costs year-round?
Dampers regulate the amount of outside air entering the unit. When they are stuck open or leak, the system continuously draws in more outdoor air than necessary. This excess air must be conditioned (heated in winter, cooled in summer), dramatically increasing the load on your HVAC systems throughout the year.
What are the main signs that a make-up air unit is underperforming or wasting energy?
Facility managers should watch for rising utility bills that can’t be easily explained, inconsistent temperatures in different zones, noticeable drafts, or persistent humidity issues indoors. These symptoms often point back to ventilation imbalances or component failures.
Is it worth replacing or upgrading an older make-up air unit?
Yes, in many cases. Older units often lack modern energy-saving features like variable speed fans, advanced temperature controls, and energy recovery systems. Upgrading to a modern, efficient unit can significantly reduce long-term operating costs and improve reliability.
Climico works with building operators throughout the region to evaluate ventilation systems, resolve common make-up air unit problems, and improve overall HVAC efficiency. If rising utility bills or ventilation issues suggest your make-up air unit may be underperforming, contact Climico to assess your system and develop practical solutions that support long-term energy performance.
If your building’s make-up air unit is driving up energy costs or creating ventilation issues, contact Climico to schedule an evaluation and learn how optimized make-up air unit performance can improve efficiency, comfort, and long-term system reliability.