Benefits of Makeup Air Part 2

Last week, we discussed just a few of the benefits of adding a Make-Up Air Unit to your commercial or industrial HVAC design. Today, we continue reviewing more great benefits as well as highlighting a recent design/build project that included MAU.

High Efficiency

Make-up Air Units are extremely efficient, and provide great bang for their efficiency buck. Direct fired units provide the best efficiency (100% thermal efficiency, 92% sensible). The make-up air is heated directly by the gas flame, eliminating the need for a heat exchanger and its associated efficiency losses. and produce the highest ROI on comfort. Many models can also be paired with a Variable Frequency Drive (VFD) for even more efficiency and comfort control.

In addition, Make-Up Air units will help other equipment work more efficiently. By pressurizing the building and eliminating negative air concerns as well as fulfilling fresh air needs with tempered air, Make-up Air Units are reducing the energy loss that comes from negative indoor pressurization and take some of the load off HVAC and other exhaust or ventilation equipment.

Low Maintenance

Per Chris Broyles, Director of Commercial Services at JK Mechanical, MAU are easy and low-cost to maintain, as they typically have few parts that need to be routinely replaced. With Direct Fired units, the same lack of heat exchanger that makes them so efficient also means less equipment and moving parts that need to be maintained. While regular maintenance is still an important part of safe and efficient operation, lower replacement part and service labor costs can add up to great savings over the life of the unit.

When to Use Make-Up Air Units

JK Commercial Service Director Chris Broyles shows us a one of the Cambridge Make-up Air Units installed at the Hollander Rd project.

Based on the benefits we’ve discussed, you can see why the JK Mechanical team recommends MAU for a wide variety of applications. In addition to the efficiency and comfort improvements they provide, the MAU indoor air quality abilities are a great fit for commercial buildings such as hospitals, warehouses, factories, and other workspaces that require high fresh air levels for safety but cannot (and don’t want to!) negatively impact occupant comfort.


In 2019, JK Mechanical’s Commercial HVAC estimator and designer Fred Bentley proposed an HVAC plan for a Design/Build project with Vanguard Development Group for a two-building new construction facility in New Holland. As this facility would house both open manufacturing, warehouse, and woodworking space as well as office space, there were a lot of considerations in play for the HVAC system design. Fred was asked to design a system with:

  • No rooftop equipment or additional weight on the structure, as a pre-engineered building
  • No internal systems, as the occupant required as much square footage inside as possible
  • Limited outdoor pad area, in order to avoid impacting yard usage as much as possible.


Based on those design asks, Fred felt that Cambridge gas fired space heaters (direct fired MAU units) were a logical fit for the space needs. “I chose the Cambridge gas fired space heaters for several factors.  Vertical foot print was smaller than 80/20 units, and fewer pieces of equipment are required. They combine space heating and required outside air since it is direct fired 100% outside air system. More efficient than 80/20 thanks to 99% burner efficiency. I have a long history with Cambridge equipment, and it was more cost effective than 80/20 and air rotation.” By utilizing MAU technology (as well as a full custom control system from Chris Broyles), Fred and our commercial HVAC were able to meet the needs of the designer and occupant while delivery efficient, customized comfort.


At JK Mechanical, our team of experienced and trained commercial estimators and designers are ready to work with you. Call or contact us today to learn more.


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