Can You Retrofit Air Source Heat Pumps?

When it comes to heating your home, there are a number of options available to homeowners.

In the past, homeowners have relied upon gas, wood, and oil to heat their homes. With technology advancing so that energy-efficient sources are available, the installation of heat pumps such as air source ones is becoming more common.

Air source heat pumps can be installed in most homes. However, installation regulations such as space requirements, clearance distances for noise, inadequate existing heating setups and poor insulation levels can make retrofitting using air source heat pumps more of a challenge.

Air source heat pumps can be a great option for your home’s heating system but retrofitting one can be more complicated and expensive compared to installing one in a new home.

Our air source heat pump was installed when the house was built and so the heating system inside was setup to work with the heat pump from the start.

Air Source Heat Pump
Our own air source heat pump wasn’t retrofitted but it can be possible to do so in most situations

Our air source heat pump works fantastically well but the house uses the right apparatus, such as underfloor heating and large radiators, to help make the most of the heat pump.

Read on to learn more about what air source heat pumps are, how they work, and the things to consider when looking to retrofit one.

Understanding How Air Source Heat Pumps Work

Air source heat pumps (ASHP’s) work by taking the heat out of the air outside of your home and delivering it inside.

This can be air to air heating so that the heat from outside is harnessed and released into the air that goes through your fan system.

Alternatively, it can be air to water heating, so the heat is harnessed from the air outside and released into the water that circulated through your water pumps, which provides radiator and underfloor heating, and can even be used for domestic hot water.

See our guide comparing air to water and air to air heat pumps for more information.

We have an air to water heat pump and delivers heat for both central heating and domestic hot water.

Air Source Heat Pump
The air source heat pump unit itself sits outside your home

In these systems, the air from outside is circulated around lines of coolant fluid inside of the system outside of your home. This warm air mixed with the refrigerant fluid causes the fluid to heat up, turning into a gas.

The warm gas travels through the lines to a compressor, which further heats the gas and compresses it so that more fluid flows through the system in a shorter amount of time.

Air Source Heat Pump Pipes
Refrigerant is carried to and from air to water heat pumps like ours, with a hot water tank being at the other end of the pipes inside our house

Once compressed and heated further, this air passes through lines called a heat exchanger. In this part of the system, the tubes of hot air are surrounded by cold air or water that absorbs the heat from the hot gas.

As a result, the gas cools down and compresses back into the refrigerant gas that is pumped outside. Meanwhile, the air or water that has been heated from the hot gas is pumped around your home.

This process allows the heat from outside to be transferred inside of your home’s air heating or water heating system.

For more information see our complete guide on how air source heat pumps work.

How Retrofitting Air Source Heat Pumps Work

Air source heat pumps do have the advantage of having a low carbon footprint.

They’re also energy-efficient, and typically have a good coefficient of performance meaning that they can generate more units of heat than the units of electricity needed to power them.

Because of these benefits, many local and national governing bodies will offer you a rebate for installing or retrofitting such a system. This incentive has encouraged many people to begin the process of retrofitting air source heat pumps.

But the conversion process isn’t always that simple.

In most houses, the furnace or boiler is the central heating location where hot air or water is produced by burning fuel such as oil and gas.

However, a heat pump and its various components will need to replace much of the existing system.

An air source heat pump will need to be placed outside, typically in a location that is open but also away from windows and neighboring properties due to noise.

Our heat pump is installed on the side of the house adjacent to the garage and away from windows and bedrooms.

Air Source Heat Pump & Air Conditioning Units
An air source heat pump (right) will need to be located in an open area on the outside of a home

See our guides on where to install an air source heat pump and air source heat pump installation requirements for more information.

A new hot water tank may be required that works with the new ASHP, along with all the associated apparatus and pipes leading from the heat pump outside.

Air Source Heat Pump Water Heater Tank
The right internal apparatus, such as this water heater cylinder tank and associated equipment, will need to be used to compliment an air source heat pump

See our article on using an air source heat pump with a hot water tank for more information.

Larger radiators, and potentially a greater number, may also need to be installed to increase the surface area and help the heat produced by a heat pump to be more easily released into a home. The installation of air ducts may be required for air to air heat pumps.

While initially this can be a lot of work and costs can be high, it can be worth it over a long period of time.

Many organizations and contractors have the knowledge and experience to retrofit your home with an air source heat pump system.

Though it can be expensive, it’s strongly recommended that an approved installer is brought on to work on the retrofit. Installing a heating system is never something that can easily, or safely, be done by yourself.

Considering Retrofitting An Air Source Heat Pump

Installers will be able to provide a solution and install an air source heat pump in most cases, but the pros and cons of retrofitting one will always need to be considered by the homeowner.

Costs for retrofitting and air source heat pumps vary but can be in the thousands. This can be significantly more than the cost to install or maintain an oil or natural gas heating system.

There can also be rules and regulations for air source heat pump placed, taking into account noise and efficiency, and significant amounts of work may need to take place inside a home, such as installation of more and bigger radiators and improving insulation, in order to make the most out of the heat pump.

The other major disadvantage to retrofitting air source heat pumps is that they aren’t the best for every environment.

Under 32°F (0°C), the system can be much less efficient. Installing solar panels with hot water or hot air capabilities may be a much better choice, or even using a ground source heat pump may work better depending on the situation.

However, grants have been available for their installation that can help to bring installation costs right down, and air source heat pumps themselves also only generate heat from a renewable energy source.

ASHP’s only require electricity as the power source, and if this electricity is also generated from a renewable source then heat pumps can be very sustainable way to heat a home.

When used with the right number and size of radiators, or underfloor heating, an air source heat pump can work extremely well in providing heat for both central heating and hot water purposes.

We’ve also had no issues with our ASHP for the 5+ years that we’ve been using it.

Can You Retrofit Air Source Heat Pumps?

Retrofitting an air source with a pump is possible in most situations.

Adequate space outside for the heat pump will need to be sought, alongside consideration of being in the open for maximum efficiency and clearance distances to neighboring properties for noise.

The internal heating system and its ability to release the heat generated by an ASHP will also need to be considered. Installation of a new hot water tank alongside pipework and associated apparatus, and improving the radiators and insulation, may be required.

A certified installer will be able to provide you the best possible solution for your home, taking into account all of the above and more.

Further Reading

Are Air Source Heat Pumps Cost Effective?

Parts Of An Air Source Heat Pump Explained

Can An Air Source Heat Pump Be Installed Indoors?

Air Source Heat Pumps & Underfloor Heating

Air Source Heat Pumps & Radiators