Difference Between AHU and RTU (With Table)

Difference Between AHU and RTU (With Table)

Decoding HVAC Systems: Air Handling Units (AHU) vs. Rooftop Units (RTU)

In the realm of HVAC (Heating, Ventilation, and Air Conditioning) systems, the terms Air Handling Unit (AHU) and Rooftop Unit (RTU) frequently surface. While both play pivotal roles in maintaining indoor comfort, they serve distinct purposes within a building’s climate control infrastructure. In this article, we will delve into the differences between AHUs and RTUs, exploring their functions, components, advantages, and applications in the field of HVAC engineering.

Air Handling Units (AHU)

An Air Handling Unit (AHU) is a critical component of HVAC systems, found in commercial and industrial buildings. It is the central apparatus responsible for conditioning and distributing air throughout a structure.

Key Aspects of Air Handling Units

  1. Air Filtration: AHUs incorporate air filtration systems to remove impurities, dust, and allergens from incoming air, ensuring improved indoor air quality.
  2. Temperature Control: AHUs are equipped with heating and cooling elements, allowing them to adjust the temperature of the incoming air to meet the desired setpoint.
  3. Humidity Regulation: Some AHUs are designed to control humidity levels within a building, which is crucial for occupant comfort and the preservation of sensitive equipment.
  4. Distribution: AHUs distribute conditioned air through a network of ducts, which supply air to different zones or rooms within a building.
  5. Variable Air Volume (VAV) Systems: Many modern AHUs are integrated with VAV systems, enabling precise airflow control to various zones and optimizing energy efficiency.

Rooftop Units (RTU)

Rooftop Units (RTUs), as the name suggests, are HVAC systems installed on the roof of a building. These units are commonly used in commercial, industrial, and residential applications.

Key Aspects of Rooftop Units

  • Packaged System: RTUs are self-contained, packaged HVAC systems that include components for heating, cooling, ventilation, and sometimes humidity control.
  • Space Efficiency: The installation of RTUs on the roof frees up valuable indoor space that would otherwise be occupied by HVAC equipment.
  • Ductwork Connection: RTUs are connected to the building’s ductwork to distribute conditioned air to different areas.
  • Outdoor Exposure: Being exposed to outdoor elements, RTUs are built to withstand various weather conditions and are designed for outdoor use.
  • Modularity: RTUs are modular in design, allowing for easy customization and scalability based on the building’s HVAC needs.

Key Differences Between AHUs and RTUs

Let’s explore the key differences between Air Handling Units (AHUs) and Rooftop Units (RTUs):


  • Air Handling Units (AHUs): Typically located inside the building or mechanical room, away from outdoor exposure.
  • Rooftop Units (RTUs): Installed on the roof of the building, exposed to outdoor elements.


  • Air Handling Units (AHUs): Primarily responsible for conditioning and distributing air within the building, focusing on air quality, temperature control, and humidity regulation.
  • Rooftop Units (RTUs): Function as self-contained, packaged HVAC systems, providing heating, cooling, ventilation, and sometimes humidity control for the entire building.


  • Air Handling Units (AHUs): Installed indoors, requiring dedicated mechanical rooms or spaces.
  • Rooftop Units (RTUs): Installed on the rooftop, freeing up indoor space.


  • Air Handling Units (AHUs): Typically designed to connect to a building’s ductwork for air distribution.
  • Rooftop Units (RTUs): Self-contained systems with built-in duct connections for air distribution.


  • Air Handling Units (AHUs): Can be customized for indoor air quality and comfort requirements.
  • Rooftop Units (RTUs): Modular design allows for customization and scalability based on the building’s needs.

Table: Summary of Differences

Here’s a summary table highlighting the key differences between Air Handling Units (AHUs) and Rooftop Units (RTUs):

AspectAir Handling Unit (AHU)Rooftop Unit (RTU)
LocationInstalled indoors, away from outdoor exposureInstalled on the rooftop, exposed to outdoor elements
PurposeFocuses on indoor air quality, temperature control, and humidity regulationSelf-contained HVAC system providing heating, cooling, ventilation, and sometimes humidity control
InstallationTypically requires dedicated indoor mechanical rooms or spacesInstalled on the roof, freeing up indoor space
DesignDesigned to connect to building’s ductwork for air distributionSelf-contained with built-in duct connections
CustomizationCustomizable for various indoor air quality and comfort requirementsModular design allows for customization and scalability


Air Handling Units (AHUs) Applications

  1. Commercial Buildings: AHUs are commonly found in office buildings, retail spaces, and shopping malls to maintain a comfortable indoor environment for occupants.
  2. Industrial Facilities: Industries such as manufacturing and pharmaceuticals use AHUs to ensure proper ventilation, temperature control, and air quality.
  3. Hospitals: In healthcare settings, AHUs are vital in maintaining sterile environments and controlling airflow in critical areas.
  4. Data Centers: Data centers rely on AHUs to regulate temperature and humidity to protect sensitive equipment.

Rooftop Units (RTUs) Applications

  1. Retail Stores: RTUs are used in retail environments to provide heating and cooling for large open spaces.
  2. Restaurants: Many restaurants install RTUs on their rooftops for efficient climate control.
  3. Schools and Educational Facilities: RTUs are suitable for educational buildings due to their scalability and ease of maintenance.
  4. Low-Rise Commercial Buildings: These units are commonly used in low-rise office buildings, banks, and small businesses.

Energy Efficiency

Air Handling Units (AHUs) Energy Efficiency

  • AHUs can have energy-efficient features such as variable frequency drives (VFDs) to control fan speed, economizers for free cooling, and energy recovery systems.
  • Precise control of indoor air quality parameters helps optimize energy consumption.

Rooftop Units (RTUs) Energy Efficiency

  • RTUs can also be equipped with energy-efficient components like high-efficiency compressors, demand-controlled ventilation, and economizers.
  • Proper maintenance and regular servicing ensure RTUs operate at peak efficiency.


In the realm of HVAC systems, Air Handling Units (AHUs) and Rooftop Units (RTUs) represent two distinct approaches to indoor climate control. AHUs focus on air quality, temperature regulation, and humidity control while distributing conditioned air within a building. On the other hand, RTUs are self-contained systems providing comprehensive heating, cooling, ventilation, and sometimes humidity control for an entire structure.

Understanding their differences in purpose, location, and design is crucial for HVAC professionals and building owners when selecting the most suitable system for a specific application. Both AHUs and RTUs have their strengths and advantages, making them indispensable components in the pursuit of indoor comfort and energy efficiency.

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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.

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