Make-Up Air Unit

A complete ventilation system consists of equal parts exhaust air and replacement air. Exhausting air is a simple concept that is understood; however, the corresponding replacement air, commonly referred to as make-up air, is often misunderstood or overlooked.

The ill effects of an unbalanced ventilation system are widespread and have a significant impact on everything from personal health to manufacturing processes.

For this reason, we will be focusing this discussion on replacement air and the corresponding make-up air unit to provide it (aka MUA unit).

It is important to know that one cannot function without the other. Simply put, for an exhaust fan to extract air, it must have air to extract.

If enough air is depleted within a space, one of two things will happen:

Most buildings are not tight enough to result in the latter, so replacement air is drawn into the building through cracks, seams, and openings around the structure.

Left uncontrolled, the air will enter through any opening it can find. Commonly referred to as “drafts”, entry can be found around doors, windows, cracks in walls, drains, roof openings, flue pipes, etc.

The heaviest influxes of air enter through open doors and windows, as these are large openings and serve as a path of least resistance.

You may have experienced heavy influxes of air through doors and windows on days with little to no wind, with air traveling fast and far and disrupting everything in its path, including both people and processes.

This is a perfect example of air stampeding in an effort to balance the building pressure.

This unintended and uncontrolled method of replacing air is inefficient, dangerous, and unhealthy. Because the air being introduced is moving at a lesser rate than the exhaust, the space remains under negative pressure.

In summary, a building under a negative is dangerous, unhealthy and costs significantly more to operate.

This negative pressure allows contaminated air, including viruses (learn how to kill germs in HVAC systems here), bacteria, and products of combustion, to remain in both the office and manufacturing spaces for longer than intended.

The decreased air exchange has damaging effects on the indoor air quality (IAQ), which compromises the overall health of the building and places personnel at risk of getting sick. Also, because of the negative pressure, all of the exhaust and heating, ventilation, and air conditioning (HVAC) equipment has to work harder to reach the original design points. This means that more energy is used to get less done.

In summary, a building under negative pressure is dangerous, unhealthy, and significantly more expensive to operate.

Whatever your building, there is a solution. An air handling unit (AHU) or make-up air unit (MUA or MAU).

We are the official distributors of the top make-up air unit manufacturers in the USA. As official representatives, we’ll be happy to help explain the best make-up air unit for your application.

What is a Makeup Air Unit?

A make-up air unit is a mechanical piece of equipment designed to provide a consistent and controlled solution to replacing the air within the space. This can be as simple as a fan blowing air into the space or a more engineered approach including tempered air, filtration, and other options.

However it is conveyed, the system is designed to introduce fresh outdoor air back to the space. A make-up air solution is recommended for buildings where environmental conditions warrant a greater need for ventilation, not only to improve the quality of the air within the building but also to protect the health of those inside.

Make-up Air Unit Diagram

What Does a Make-up Air Unit Do?

Simply put, a make-up air unit provides replacement air. The purpose of a make-up air unit is to replace the air exhausted from a space by general ventilation, process equipment, heaters, and other HVAC equipment. By replacing the air, the building is brought to a neutral or predetermined building pressure.

This balanced building pressure allows the building to operate as intended, with HVAC systems, manufacturing processes, etc. performing at peak efficiencies.

The result is a healthy building with good indoor air quality (IAQ), a healthy staff, and lower energy costs.

The costs of a makeup air unit are often recovered through the energy savings made possible by lesser HVAC demands, lower exhaust demands, higher production levels, increased production, decreased personnel sick leave, and other corresponding factors.

Make-up air is a significant benefit to any space using exhaust.

Make-up Air Units Help Solve a Distribution Center's Sanitation Conundrum

Benefits of Make-Up Air System

Make Up Air Unit Features

To best understand a traditional makeup air system, we should first start with its construction. In its most basic form, a makeup air unit is a fan inside a metal box.

These fan boxes are often modular and can be built to accommodate many requirements.

A traditional makeup air unit typically includes:

This is the basic construction, but certainly not the limitation.

Contact a Pro to help find the best make-up air unit for your application

We are official distributors for the manufacturers listed below. As official representatives, we’ll be happy to help explain the best make-up air unit for your application. Contact us for a quote or any information regarding their products.

Types of Make Up Air Units

Additionally, there are many types of makeup air units that can be provided with a variety of heating and cooling options, including:

Make-up air systems are utilized in commercial, institutional, and industrial applications. As each segment is different, they often serve a variety of functions.

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Commercial Make Up Air Units

Commercial make-up air units are able to offer fresh MUA fans for all types of exhaust hood sizes with various airflow rates up to 100,000 cfm (cfm Wikipedia).

There are many configurations involved with commercial MUA systems. They typically have filters made of powder-coated steel and also heavy-gauge galvanized steel. Most models have blower fans that are powered by belt-drive motors and are enclosed in weather-protected cabinets for year-round protection.

A commercial space such as an office building utilizes makeup air to pressurize the various floors due to the negative pressure produced by elevator shaft effects and exhaust systems.
A warehouse utilizes makeup air to provide the required air exchanges and is typically used to heat and cool the building.
The institutional segment often applies makeup air to filter large quantities of air to provide high air exchange rates of clean fresh air.
The industrial sector has the most diverse usage applying makeup air equipment for general air replacement, air circulation, heating, cooling, filtration, recirculation, etc.

The focus of our discussion will be on the industrial marketplace.

Industrial Make Up Air Units

Industrial make-up air units are designed to provide large quantities of fresh, conditioned air to industrial or commercial facilities to maintain a comfortable and healthy indoor environment.

These units typically operate by drawing in fresh outdoor air, filtering it, and then conditioning it to the desired temperature and humidity levels. They are commonly used in facilities with high ventilation requirements, such as factories, warehouses, and commercial kitchens.

Industrial make-up air units can come in different types, including direct-fired, indirect-fired, and electric heat models, and they can be configured in various ways depending on the specific needs of the facility.

These units are typically mounted on the roof or on the side of the building, and they can be designed to provide either 100% fresh air or a mix of fresh and recirculated air.

MUA Mounting Options

An industrial makeup air unit can provide as little as a couple hundred cubic feet per minute or as much as several hundred thousand cfm. In addition, the industrial MUA unit provides several other mounting options and a significantly broader operating range.

Breath of Fresh Air

Buildings with contaminated air, such as manufacturing or processing facilities, typically introduce 100% outside air (O/A) or fresh air. This ensures the process equipment and employees breathe fresh, clean air.

Cleaner facilities, such as warehouses and distribution centers, can often include a recirculation feature that allows for high volumes of air to be recirculated from the building space.

This recirculation feature allows for large amounts of air to be conditioned at a low operating cost while still introducing enough fresh air to provide the air changes necessary to meet local codes.

The industrial makeup air equipment also provides a wide offering of heating and cooling options that can be installed together or independently.

In all cases the intent is to provide healthy, tempered air to the space. The fresh, conditioned air provided makes for a better working environment resulting in less complaints and greater production.

The industrial makeup air equipment also provides a wide offering of heating and cooling options that can be installed together or independently.

Make-Up Air Unit Systems

In many cases, make-up air systems require conditioning. Most can be provided with heating and cooling options to accommodate the space’s requirements.

The following are additional components that are available for custom make-up air units:

Heating Options

Cooling Options

Electric MUA

Electric MUA is commonly applied where there are frequent air changes. These heaters can be installed indoors or outdoors.

Common applications are for kitchens, factories, and similar commercial & industrial environments. Electric make-up air units can be used as combination packages that include exhaust and supply fans that are mounted on the same roof.

There are many variations of indirect gas-fired make-up air systems, such as:

Chilled Water Cooling

The chilled water cooling module is quite common in the industrial sector. The coil is mounted within the MUA housing, and air is drawn over it to provide a temperature reduction. The coil is fed by a stand-alone water chiller, which delivers cold water to the coil.

An incredibly effective means of cooling, chilled water is most often used in larger air handlers. These units can be installed both indoors and/or outdoors, depending on the application.

Chilled water air handlers can be used in combination with other modules, such as direct or indirect gas-fired heaters.

Evaporative Cooling

The evaporative cooling module is designed to deliver humidified, cooled air to areas that are hot and dry. Mixing the cool moisture with hot, dry air will provide a significant temperature drop.

These units can be installed both indoors and/or outdoors, depending on the application. Evaporative air handlers can be used in combination with other modules, such as direct or indirect gas fired heaters.

These units can be installed both indoors and/or outdoors depending on the application. Evaporative air handlers can be used in combination with other modules, such as direct or indirect gas fired heaters.

Untempered (Fan Box)

A make-up air unit fan, also known as a fan box, brings in fresh outside air without a heating or cooling element. This provides the required air changes while maintaining, or possibly reducing, the building temperature.

Fan boxes are ideal for applications where specific operating conditions are not a requirement. They are great for summer cooling and can provide a clean replacement air solution at minimal equipment and operating costs.

Make Up Air Manufacturers

We are the official distributors of the top-rated make-up air unit manufacturers in the USA. As official representatives, we’ll be happy to help explain the best make-up air unit for your application. Contact us for a quote or if you have any questions regarding industrial or commercial MUA.

Some manufacturers we work with for make-up air equipment include AbsolutAire, FloAire, and Moffitt Corporation.

Make-Up Air Units Installed

Providing MUA's to the Following Industries

Providing Ventilation Equipment to the Greater Chicago area & Ship Nationwide

R. Williamson & Associates can provide you with fast quotes on the correct make-up air unit for your application.

We are official representative covering Illinois, Wisconsin, Minnesota, Michigan and Indiana.

We can also send out a trained specialist to assess the area and make certain the proper unit is being used for your specific application.

Manufacturers We Represent

At R. Williamson & Associates, we pride ourselves on being the official distributor for leading industrial ventilation manufacturers. Our commitment to quality and efficiency ensures that our clients have access to the best products in the market, tailored to their specific industrial or commercial needs.

Why Choose Us?

Exclusive Access: As the official distributor, we provide exclusive access to products that cannot be ordered directly from the manufacturer. This ensures that our clients receive genuine and top-tier products backed by industry leading warranties.

Expert Assistance: Our team is dedicated to assisting you in finding the right product for your industrial or commercial application. We understand the complexities of ventilation needs, and we’re here to guide you through the process.

Streamlined Ordering Process: We facilitate the ordering process by acting as a liaison between the customer and the manufacturer. Our expertise ensures that the proper equipment is ordered the first time, saving you time and resources.

A Wide Range of Manufacturers: We represent a diverse list of manufacturers, each known for their excellence in the field of industrial ventilation. This allows us to offer a wide variety of solutions, catering to the unique requirements of each project.

Our service is more than just a distribution channel; it's a partnership that aims to solve your main pain points in obtaining the products you need.

By choosing R. Williamson & Associates, you are opting for a seamless, professional, and reliable experience in industrial ventilation procurement.