Heat From Air
Air-to-air Heat Pumps
What is an air-to-air heat pump?
Air to air heat pumps transfer heat from the outside air to inside your home, increasing the temperature of the air in each room. This warm air enters your home through a series of fan coil units, or ‘blowers’.
People sometimes refer to these heat pumps as air conditioning. Many think of air conditioning as cooling, but it can also provide heating.
These particular heat pumps do not heat water delivered to the taps, so you will need to consider an alternative way of heating water for showering and bathing.
Is an air-to-air heat pump right for me?
In the UK, installers don’t typically use air-to-air heat pumps for heating larger homes. Most domestic installations use air-to-water systems. Installers more often place these heat pumps in smaller properties, such as park homes or flats.
In other parts of Europe, air-to-air systems are more common. These systems are popular partly because they can cool as well as heat, which is useful in warmer climates.
There are a few things to consider when deciding whether these heat pumps are right for you.
You’ll need to fit a unit to a wall or place it on the ground near your house. It will need plenty of space around it to get a good flow of air.
Most UK homes use radiators or underfloor heating to distribute heat to each room. People commonly refer to these systems as ‘wet’ heating systems. Air-to-air heat pumps have the advantage of not requiring a wet central heating system to warm the home.
The heat pump delivers warm air through fan coil units (‘blowers’) or air ducting pipes. Installers usually mount blowers high on the wall, which is useful when wall space is limited. New build properties are more likely to use ducting systems, with ducts mounted inside ceiling voids to keep them unobtrusive.
Air-to-air heat pumps can be single-head or multi-head, where ‘head’ refers to the number of blowers used. A single-head air-to-air heat pump has one outside unit and one blower inside. A multi-head air-to-air heat pump has a single heat capture unit outside and multiple blowers inside.
In the UK, single-head air-to-air heat pumps are typically used only in the smallest homes or for single-room heating. For homes with more than two rooms, you likely need a multi-head air-to-air heat pump or a ducted system.
Since they don’t need a wet central heating system, air-to-air systems with blowers can be quick and cheap to install. Multi-head installations require pipes from the outside heat capture unit to each blower, similar to how boilers need pipes for radiators in each room. Typically, installers run these pipes in slim plastic channels around the room’s upper edges to keep them as unobtrusive as possible.
Since these heat pumps don’t heat hot water, you will need another method to heat water for showering, bathing, and hot taps. Fortunately, there are several options available, and the best choice for you will depend on factors like your household’s hot water needs, as well as any space or budget considerations.
You could consider a hot water cylinder fitted with an electric immersion heater, or you might consider using electric showers and ‘point of use’ water heaters. Point of use heaters could use either gas, LPG or electricity to heat the water. Gas-fired heaters will need a flue, whereas electrically heated units can simply be mounted underneath the sink out of sight.
Running costs will depend on how your heat pump is designed and how it’s operated. Savings on your energy bill will also be affected by the system you are replacing.
There is currently very little independent data on how air-to-air systems perform in the UK, so it’s difficult to predict how much money you would save by fitting one. However, we can give some general guidance on what to expect.
Please head to our in-depth heat pumps guide for more information.
Saving money on fuel bills isn’t everyone’s primary motivation for installing a new heating system, but you need to be sure you can afford to run the system once installed. You should ask your installer for an indication of running costs based on their design of the system for your home.
The pipes running to the blowers are all connected to the outside unit. For this reason, blowers are often installed on the inside of an exterior wall near the outside unit, to reduce the length of pipes required internally. Where multi-head systems are planned, the installer would normally aim to minimise the lengths of pipes being run to each blower location, so ask anyone surveying your house about the possible pipe routes so you understand before they start work.
Installing ducted systems.
Builders typically use ducted systems in very energy-efficient houses, such as ‘Passivhauses.’ Some people refer to certain ducted systems as exhaust air heat pumps (EAHPs), though EAHPs can also supply hot water. Air is not able to carry large amounts of heat in the same way that a wet central heating system can, so ducted systems may not be suitable for older or larger houses with a high heating requirement.
Installers design the ducts to move large volumes of air through pipes slim enough to hide inside ceiling voids. Inside each room, only two ceiling-mounted grills are visible; one for air flowing in and one for air flowing out. Installers typically place an air handling unit, roughly the size of a boiler, in a loft or utility room to warm the air.
Further Reading...
Your Green Future
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Your green future
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Your Green Future
Starts Here
Your green future
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