Air source heat pumps are becoming a more popular heating and cooling and system for a home but there are different types of air source heat pump to choose from, and the way in which they move air through a home can differ.
These variations can include ducted and ductless air source heat pump systems, which typically work with the air to air form of air source heat pump.
A ducted air source heat pump setup works with a central indoor air handling unit and a network of ducts to move air around a home. In a ductless setup, one or more air handling units work with an outdoor air source heat pump to heat or cool individual areas.
Both ducted and ductless systems used an external air source heat pump, but the difference lies in their internal setup and the connections to the heat pump.
Each type will have its advantages and disadvantages and so comparing the pros and cons of each can help you to decide which one suits your needs.
Our own air source heat pump is the air to water type and uses a water-based central heating system and so can’t work with ductwork. It’s therefore a ductless system and moves heat from the external heat pump to the indoor system via refrigerant within pipes.
We discuss more about the differences between ducted and ductless air source heat pump systems in more detail below, including the pros and cons of each, and which could be the most ideal setup for your home.
Ducted & Ductless Air Source Heat Pumps Explained
The main difference between ducted and ductless air source heat pump setups are that:
- Ducted systems use ductwork to move air around a home from one central air handling unit.
- Ductless systems use one or more air handling units located in various rooms around a home and distribute air directly into that area without the use of ducts.
Both setups will use an outdoor air source heat pump like the one we have below.
Ducted Air Source Heat Pumps Explained
Ducted air source heat pump (ASHP) setups differ to ductless in that, as the name suggests, ducts are used to help move air around a home.
Ducts can be preexisting and already built into a home for use with an existing system, or ductwork can be installed into a home as part of the heat pump installation.
A new air source heat pump setup can typically work with existing ducts if they are sufficient. If ductwork needs to be installed, then this can be added cost at installation.
To use ducts with an air source heat pump, a central indoor air handling unit will typically be required.
The central air handler will ideally be located somewhere in the middle of the home, and ductwork will distribute air across a home from this central air handling unit, with one or vent openings within each room or space.
An external air source heat pump unit will transfer heat to the central indoor air handling unit through refrigerant within pipes.
In heating mode, a central air handler will transfer this heat to the air within a home and force heat around the house to the individual rooms via the ductwork.
In cooling mode, this process will work in reverse and an air source heat pump will remove heat from the air in a home to provide cooling.
It may also be possible to have a package air source heat pump setup where the central air handling unit is located outdoors with the main heat pump unit as one system, from which air is move around a home within ducts.
Ducted setups only work with air to air heat pump systems, where temperature control is provided through heating or cooling the air directly.
The alternative ASHP setup to this would be air to water heat pump systems where a water-based central heating system is used alongside apparatus such as underfloor heating and radiators. No ductwork would be required with this type of heat pump. See our article comparing air to air and air to water heat pumps for more information.
Ductless Air Source Heat Pumps Explained
Ductless air source heat pumps don’t use to ducts to distribute air within a home, and any existing ductwork wouldn’t be utilized and no new ductwork would need to be installed alongside the heat pump.
A ductless setup is similar to a ducted in terms of using an external heat pump unit with internal air handling unit and refrigerant pipes connecting the two.
However, the air handling unit as part of a ductless system delivers air straight into a room or space.
There are various types of air handling unit such as floor-mounted, wall-mounted and ceiling-mounted but all provide the same function of serving heated or cooler air directly in the room its installed within.
As a ductless air handling unit only serves one particular area, it can be necessary to install more than one air handling unit to serve a whole house. A ductless air source heat pump system can therefore have multiple refrigerant lines going to several air handlers.
This makes ductless setups more ideal for smaller spaces or where whole-house cooling or heating wouldn’t be required. Ductwork can also be expensive and time consuming to install in a home that doesn’t already have existing, which can make a ductless setup more favorable in such scenarios.
Ductless air source heat pump setups can also be referred to as ductless mini splits, or just mini splits.
Mini splits can be ducted or ductless. However, mini splits are air source heat pumps only if they provide both heating and cooling. Some mini splits are solely air conditioners.
See our article on air source heat pumps vs mini splits for more information.
Ducted vs Ductless System Similarities
Ducted and ductless are only typically referred to when talking about air to air heat pump setups, where heating and cooling is provided using space conditioning with an air handling unit.
Air to water heat pumps are through the way they work ductless only (as they’re water-based systems) and so there would be no need to differentiate between the two.
Whichever setup, ducted and ductless, is chosen it will use an external air source heat pump unit located outside a home.
This main ASHP needs to be located outside so that it can extract heat from the air.
This outdoor heat pump will typically work exactly the same, no matter the indoor setup chosen, but the main difference could be the number of connections going indoors.
See our article on where to install an air source heat pump for more information.
Pros & Cons of Ducted vs. Ductless Air Source Heat Pumps
Pros & Cons Of A Ducted Air Source Heat Pump
Here are the advantages and disadvantages of a ducted air source heat pump:
| Pros | Cons |
| Suitable for houses with existing ductwork | The setup needs forced air handler units |
| Heating and cooling for the entire property | Requires air return vents and ductwork |
| Powerful circulation of warm and cool air | Energy loss due to supply and return ducts |
| Concealed ducts and recessed vents or registers | New ducts and air handlers are expensive |
| Can be less expensive (excl. ducts and air handlers) | Dust can build up within the ducts |
A ducted air source heat pump can lose a lot of energy to heat or cool the spaces inside the ducts, and ductwork can leak and lose heat energy. Energy.gov explains that ducts can account for more than 30% of energy losses.
Even if you use dampers and shut a particular zone or floor, some portions of the duct are still getting heated or cooled when you run an air source heat pump. So, such setups can waste some energy.
On the positive side, ducted air source heat pumps have only one unit inside for the outdoor heat pump unit. Thus, you don’t need multiple lines for separate indoor heads. The forced air handlers necessary are simply large blowers.
Pros & Cons Of A Ductless Air Source Heat Pump
Here are the advantages and disadvantages of a ductless air source heat pump:
| Pros | Cons |
| Ducts and forced air handler units aren’t required | Not all indoor heads are concealed |
| Heat and cool one room or up to 4 or 5 zones | Not ideal for very large properties |
| Excellent energy efficiency | Every indoor head needs a conduit |
| Exceptional temperature control in every room | Can be costlier than ducted units (excl. ducts) |
| Air return vents aren’t necessary | |
| Installation can be simpler, quicker, and less intrusive |
Ductless air source heat pump setups use one indoor air handling unit for each area, with a particular air handler providing heating or cooling functionality for that specific area only.
It can be possible to expand the zoning to 4 or 5 rooms, subject to the air source heat pump’s capacity, and using indoor heads for each zone or room. This setup would allow you to control a room or zone’s temperature without any influence of the settings in another part of your house.
The temperature control and lack of energy loss due to the absence of ducts can help reduce your overall electricity consumption. Furthermore, remodeling of a home isn’t required to install new ducts.
Some people prefer the neat interior decor of concealed ducts, vents, or registers, but a ductless air source heat pump will need an indoor head. A wall-mounted indoor head is somewhat protruding, but you can work around it by getting cassettes that are recessed and installed flush with the ceiling.
Furthermore, there are floor-mounted indoor heads if you don’t want a unit in the ceiling. Unlike wall-hanging indoor heads, the floor-mounted units don’t affect the headroom or shoulder space. Also, the low-profile installation near the floor helps make such units less conspicuous.
Air Source Heat Pumps: Ducted, Ductless, or Both?
Ducted air source heat pump setups can be more feasible when a home has appropriate existing ductwork and when whole-house heating or cooling is required. Ductless are more ideal for smaller spaces, homes without existing ductwork, and controlling temperatures in specific rooms.
There are a few scenarios when you can assuredly choose one type of air source heat pump over the other. Here are two instances:
- A ducted system can be practical and more affordable if you have existing ductwork and you need to heat and cool the entire house.
- A ductless setup can be the more feasible option if you need to heat and cool only one room, or a few isolated zones of your house, with greater individual temperature control, and when there is no existing ductwork.
There is a third option for homeowners if neither ducted nor ductless emerges as the undisputed winner. The solution can a ducted/ductless air source heat pump or mini split.
A ducted/ductless air source heat pump or mini split has one outdoor unit with the compressor and condenser. You can connect one or more ducted and ductless indoor units using dedicated copper lines for the refrigerant or coolant. Each indoor system would have a separate conduit.
For example, you could have one ductless indoor head for a medium sized living room and a ducted setup with registers in the ceiling for the bedrooms. This type of setup gives you the best of both worlds.
Here’s an example of a 48,000 BTU Mitsubishi ducted/ductless setup for 4 zones:
Further Reading
Parts Of An Air Source Heat Pump Explained
How An Air Source Heat Pump Works
Air Source Heat Pump Pros & Cons