The infrastructure for a ground source heat pump could need a considerable amount more space than an air source heat pump depending on the installation.
The extra space is required because of how ground source heat pumps work.
Ground source heat pumps use ground loops, buried in the ground that circulate anti-freeze and water.
Ambient heat is absorbed from the earth with the heat extracted via a heat exchanger with the extracted heat pumped into the heating system of your home through a series of pipes.
The amount of space that you need for a ground source heat pump will depend on the type of installation you require. Ground arrays can be very large and the space you will need to install one will depend on the type of heat pump you want to install.
Horizontal Ground Source Heat Pump
Horizontal ground arrays use slinky pipes buried in trenches dug 1.2m below the earth’s surface to collect the ambient heat needed for your heating system. They are the most common installation method for ground source heat pumps in individual properties.
The amount of slinky pipes that you will need depends on the heat load requirements of the property. It is generally recommended that for each 1kW of heat you will need 10m of trenching with slinkies.
You will need around 700 square metres of space for a horizontal ground source heat pump to be installed. Most heat pumps will need 3 x ground loops at 200 m in length that are spread out independently over an area.
700 square metres is around the size of 2.5 tennis courts.
This means, with UK gardens averaging 12m squared, a horizontal ground source heat pump won’t be a viable option for most UK homes.
Vertical Ground Source Heat Pump
A vertical ground array works in the same way as a horizontal ground array, but is installed vertically, rather than laid flat below the surface of the ground.
Vertical ground arrays are used to collect heat from beneath the ground, they can be a great option if you are short on space and don’t have room for a horizontal ground array.
Boreholes will help to minimise disruption to your property as you will generally only need around 150mm width of space per borehole.
This means boreholes will need to be drilled into the external area where you are installing your loop array. Normally you will only require one borehole per property. You will normally need at least 1 borehole for every 6kW of energy needed. This will equate to a minimum of 3 boreholes, similar to horizontal ground source heat pumps, for most UK homes.
Boreholes can range between 60m to 200m deep, which means sewers, gas pipes and other obstacles can slow progress or make excavation impossible.
These requirements mean that, theoretically, you could install a vertical ground source heat pump in a UK garden, with only around 11 square metres of garden needed to evenly space the boreholes.
However, you must remember that each hole will need to be 60 – 200 metres deep, so will need to be drilled far away from the foundations of your property.
Your garden will also need to be large enough for the machinery required to operate, drill the boreholes and lay the ground loops to make your project feasible.
Vertical ground arrays are often more expensive than horizontal ground arrays, however become more affordable when they are installed as part of a shared ground loop arrays. The extra cost is due to the equipment that is needed to install the borehole.
If you were installing multiple boreholes for a shared ground loop array scheme, they will need to be placed between 5 to 6m apart.
You’ll also need space for pipes for the fluid to enter your home into the heat exchanger.
You don’t need planning permission for a heat pump because they come under permitted development.
You will however need to get a geological survey before drilling boreholes to check the type of ground that you are drilling into. The installer will be able to use this to help design the borehole as different conditions have different heat characteristics.
Interior Space Required for Ground Source Heat Pumps
The interior space required for both types of ground source heat types is much more similar to a traditional gas boiler. Both horizontal and vertical ground arrays work with the same internals; a heat pump unit and heat exchanger and a water storage cylinder.
You will need space for;
- a hot water cylinder (usually around 1.5m x 0.7m)
- The heat pump itself (usually around the size of a conventional gas boiler, 0.7m height x 0.3m depth x 0.4m width)
- An alternative is a monoblock heat pump system, that includes the cylinder and heat pump together in a single unit. (commonly the size of a fridge freezer (1.91m height x 0.6m width X 0.65m depth)
The size of the ground source heat pump you buy will depend on the heat load that you have. Some ground source heat pumps are small enough to fit in a kitchen cupboard, whereas others are slightly larger.
Radiator Sizes for a Ground Source Heat Pump
Like air source heat pumps, ground source heat pumps have a lower flow temperature than a gas boiler, usually around 50° – 55°, although some claim to heat water up to 65°C.
A lower flow temperature will mean you may need larger radiators installed in your property to help keep internal temperatures consistent, even when temperatures drop outside.
Recommended radiator sizes for ground source heat pumps are usually recommended to be 2.5 times larger than ordinary radiators installed for a gas boiler.
- 10 radiators in the average home at around; 0.4m x 0.4m (0.16 square metres, per radiator or 1.6 square metres in total)
- 10 radiators x 1m x 1m (1 square metre per radiator or 10 square metres in total)
A recommended alternative to radiator upgrades can be underfloor heating but this can add additional cost and time to your project and may not be suitable unless you are looking to fully renovate your home.
Total Space Required for a Ground Source Heat Pump
External space: 700m squared for ground arrays.
11 metres square, but with 100m boreholes if you’re installing a vertical heat pump.
Internal space: 13.6m squared for internal heat pump components, water cylinders and large radiators around your home.