Answer: A ground source heat pump needs more space than an air source heat pump. A typical horizontal system requires around 700 square metres. A vertical system needs enough space for the drilling rig to access the site, but boreholes are only around 20 centimetres wide. If multiple boreholes are needed, these are placed 5-6 metres apart.

What is a ground source heat pump?

Ground source heat pumps (GSHPs) extract heat from the ground. This heat is extracted from rock or surface soil, and can also be extracted from underneath lakes and riverbeds.

There are a couple of options for ground source heat pumps; you can drill a deep borehole or lay heat collectors in shallow trenches. We will discuss the sizings in more detail in the next section.

A ground source heat pump will circulate a solution of water and antifreeze around collectors called ground loops.

This is what is laid in trenches or boreholes. This absorbs the heat underground and puts it through a heat exchanger into the pump. It is an efficient method of heating residential and commercial buildings in the UK, offering heat all year round.

Also read: The benefits of a heat pump

How much space do you need for a ground source heat pump?

A ground source heat pump requires more outdoor space than an air source heat pump. This one reason is why air source heat pumps are the most common form of heat pump in the UK. Let’s take a look at how much space you need for horizontal and vertical GSHP systems.

Horizontal ground source heat pumps (trenches)

Horizontal systems are preferred, mainly due to reduced costs when compared to vertical systems. However, they do require a larger amount of outdoor space.

The details are perfectly summed up on our Information Site:

“While there are of course other factors to consider when sizing a system, it’s fair to suggest that as a guide, a 11kW Vaillant FlexoTherm ground source system would require around three ground loops, each at 200 metres in length. A minimum land area of 700 square metres would be necessary for loops of this size to be laid. In order to visualise how the ground loops are laid within this space, imagine that each loop is laid as a rectangle with 1 metre of separation – the rectangle formed by the loops would be 7 metres in width by 100 metres in length.”

Vertical ground source heat pumps (boreholes)

Vertical systems are often more efficient, due to a constant temperature and the lack of impact from the changing seasons. These systems are often chosen due to lack of space for trenches, or in situations where the earth is not suitable for horizontal systems.

In terms of space, the main issue is access for the drilling rig. This can be tricky in confined built-up areas. For the typical UK home, one borehole is enough. This borehole is perhaps 0.25m across, and up to 100m deep. Loops are then placed into the hole, feeding into the system in a nearby plant room. If multiple boreholes are needed for larger properties and/or district heating systems, these are placed around 5-6m apart from one another.

You can watch this video on our YouTube channel of borehole drilling on a project from 2019. This project used a Vaillant FlexoTherm heat pump you can see the videoa and read more about it on our blog Vertical Borehole Drilling.

The space for a plant room

With regards to space needed inside your property, you will require a plant room to host the ground source heat pump system. A plant room usually needs to have a 1 x 2/2.5 metre footprint, subject to the system size. This should be considered before the start of the project.

For more information about what type of heat pump you need, and for advice about heat pumps, contact IMS Heat Pumps today. If you’d like to see how much a ground source or air source heat pump can save you, and how much the Renewable Heat Incentive will pay you just get in touch!