What’s the Difference Between FCU vs AHU?

In simple terms, an air handling unit (AHU) is a component of an HVAC system that cools and distributes air into the space through a duct.

A fan coil unit (FCU) is a standalone system that circulates the existing air in a small space, but it can also be a part of an HVAC system.

FCU vs. AHU

Air Handling Unit (AHU)

Air Handling Unit (AHU)(Source: amedeoemaja via DepositPhotos)

You will find a comprehensive overview of AHUs in one of our earlier posts, but to summarize: an AHU is a system that conditions and circulates air through the building’s duct. It comprises of multiple components, such as a blower, sound attenuators, and cooling and heating coils.

Each AHU component is a system in itself. In fact, you have multiple design and configuration options for each one, enabling you to build an AHU centered on your building’s specific needs.

The upfront selection and installation process involved with AHUs is extensive — and expensive.

You must configure your AHU system correctly to ensure that your HVAC system runs efficiently. An inefficient HVAC system consumes excess energy and raises your building operating costs.

In addition, an inefficient HVAC system can also fall into disrepair, which will cause maintenance issues and escalate your building lifecycle costs.


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Fan Coil Unit (FCU)

Fan Coil Unit (FCU)(Source: leisuretime13 via DepositPhotos)

An FCU is not as complex or extensive as an AHU. It’s a singular system that can operate on its own to circulate air in an area without ductwork.

One major difference between FCUs and AHUs is that AHUs can bring in outside air and heat or cool it (i.e., conditioning). However, FCUs can only condition the air that’s already present in the area by pulling it in and moving back out through its heating or cooling coil.

As a result, FCUs are typically used to heat or cool small areas, such as a private gaming room in a casino. The typical FCU will cover a space of 150m2.

AHUs are more common in large buildings with a centralized HVAC system, such as Underfloor Air Distribution (UFAD). AHU-based HVAC systems are also less noisy than FCUs.

On the other hand, FCUs are also much cheaper to procure and install than AHUs. You can also get FCUs in a variety of configurations, including floor-mounted and ceiling.

The cost and variety of configuration options make FCUs attractive for houses and apartments without HVAC. However, FCUs might also be sought to support an AHU-based HVAC system by covering areas that are not connected to the HVAC’s ductwork.


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Which One Do I Select?

Your selection depends on your specific building needs. If controlling cost and reducing project complexity is the primary goal, then you may prefer FCUs over AHUs.

However, a large office building requiring ducts to diffuse and replace air will require an AHU.

In fact, if you have a large HVAC project, then you should begin examining your AHU-based options, such as UFAD. While a costlier and more complex undertaking, you can absolutely design and implement a complex HVAC project within budget and timelines.

AirFixture helps architects and engineers deliver building projects within budget and timelines by designing, delivering, and installing UFAD HVAC systems. See our FREE guide about UFAD to understand how to provide an HVAC system that lowers building OPEX.