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What is Makeup Air, and Why Is It Important?

All sealed indoor buildings create an air pressure imbalance. From the smallest household kitchen to the largest industrial warehouse, the indoor air pressure tends to be lower than the outside. This is usually caused by household appliances that push or pull air, or it can be due to the building’s layout. 

Whatever the case, the net effect is that outside air tends to get sucked into the building, which can result in detrimental effects for occupants and the building structure alike. This is where makeup air comes in.

In this article, we discuss the concept of makeup air, its effects, and why it matters.

What is Makeup Air?

Makeup air is controlled outside air that replaces the air exhausted from inside the building. Most indoor buildings have appliances that push or pull air, such as fans, range hoods, and clothes dryers. Without a makeup air system, this depressurizes the interior, and causes outside air to be sucked in. 

Many household appliances tend to suck air in or out of the house, causing an air pressure imbalance.

makeup air home

How Does Makeup Air Work?

Nature abhors a vacuum. When there is lower pressure inside a house or building, air from the outside will rush in to equalize the pressure.

Air flows through the path of least resistance. Unless the building is designed with dedicated airways, this outside air will get sucked in through doors, windows, weatherproofing, and gaps in the walls or foundation of the structure.

What are the Effects of External Air Pressure?

Unless properly channeled and filtered, makeup air can cause a number of detrimental effects to both the occupants of the building, as well as the building itself.

These include:

X Poor air quality

External air sources can consist of smog, toxins, allergens, and environmental pollutants. These can degrade the air quality indoors and cause long-term health problems. Noxious gasses, fumes and carbon monoxide from the fireplace or furnaces may also be trapped inside the house instead of being vented.

X Unwanted drafts

Since air follows the path of least resistance, it can cause uncomfortable drafts even in seemingly sealed rooms. This will be more noticeable in older or poorly sealed structures.

X Structural damage

Outside air can seep in through gaps in doors, windows, walls, ceiling and the building’s foundation. Over time it causes premature wear and tear in weatherstripping and structural support.

X Higher costs

Makeup air can cause havoc with the interior climate. The thermostat may struggle to maintain room temperature due to air infiltration , leading to larger bills. It can also take a toll on air conditioners and heaters, forcing them to work harder to maintain the desired room temperature. This leads to more frequent breakdowns and lower operational lifespan.

Why is Makeup Air Important

makeup air pros

✔️ Better air quality and safety

Makeup air is properly screened and filtered for environmental pollutants, toxins, and allergens.

✔️ Comfort

A constant flow of outside air can lead to noticeable drafts or warmer / chillier room temperature. A makeup air unit eliminates drafts and cold spots.

✔️ Lower utility costs

Makeup air units ensure that indoor temperatures remain constant and less prone to wild temperature fluctuations caused by external air.

✔️ More efficient HVAC

Many units condition incoming makeup air so that heaters and air conditioners don’t need to work as hard to maintain the indoor climate. This results in less wear and tear, lower filter clogging, and longer operating lives.

What are Makeup Air Units?

Now that we’ve established the concept of makeup air and its importance, how can it be regulated? Simple: by using makeup air systems.

Make up air units or MUAs are devices designed to replace the air that gets exhausted from the building. It works in conjunction with the ventilation system to ensure that equal pressure is maintained, and that any makeup air passes through filtered channels before circulating indoors.

A MUA can range from simple through-the-wall units for residential homes to larger, more powerful systems designed for warehouses and condominium buildings.

Where are Makeup Air Systems Required?

Residential homes

residential makeup air

  • Tightly sealed houses can result in unequal pressure, even when just opening doors. 
  • Some powerful rangehoods can cause negative air pressure in the kitchen 
  • Other household appliances can suck air out of the house, causing unfiltered air to seep in and exacerbate gaps, holes or cracks in the exterior walls and in weatherstripping.
  • Even a bathroom exhaust fan can cause air imbalances.

Dormitories and condominiums

  • Multiple units, entrances and hallways tend to destabilize pressure equilibrium
  • Lack of makeup air can result in odors and cooking fumes being noticeable from adjacent units

Hotels and resorts

  • There are professional standards regarding minimum ventilation for motels, hotels, and resorts.
  • These cover air shifts for different areas of the building, from the lobby and hotel room to multipurpose function halls.

Industrial structures

  • Makeup air systems ensure adequate ventilation for workers
  • The system also remove industrial byproducts like contaminants and fumes

Commercial kitchens

  • An industrial makeup air unit is required for restaurants and commercial kitchens to ensure proper exhaust and ventilation for kitchen workers.

Healthcare facilities

  • The spread of infectious diseases is prevented through clinical-grade filtering a and multi-stage microbial treatment
  • Since patients have more delicate requirements, medical makeup air systems must also adhere to strict regulation regarding humidity, temperature, and minimum air changes per hour.

Educational institutions

  • There are specific guidelines covering classrooms for different age groups.
  • Some areas of the school like science labs and metal or woodworking shops also require more robust makeup air to prevent fume buildup.

Office and corporate spaces

  • Makeup air is essential for office spaces, considering that employees spend at least 8 hours per weekday sharing the same interior space. 
  • Air change standards depend on the size, occupancy and layout of the office.

What is the Difference Between Makeup Air and Regular Ventilation?

A standard ventilation fan is designed to bring in outside air as-is without any heating or tempering. This makes them useful for areas with temperate climates year-round.

In contrast, a makeup air unit heats or tempers the outside air before circulating it indoors. This makes them more suitable for areas that experience different seasons. It also allows the indoor heating or cooling system to work more efficiently.

In the next article, we discuss the different types of makeup air units for various applications.

Mickey Luongo

Mickey is the resident heating and air conditioning expert with over 15 years of experience in the industry.

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