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Home cooling

The heat pump that warms your winter can cool your summer.

Modern, well-insulated homes hold on to heat brilliantly — which is exactly why they can get uncomfortably warm in July. A ground source heat pump can cool your home using the same boreholes that heat it, so summer comfort comes from the system you already own.

Talk to our team See how free cooling works
MCS certified installer 20+ years' experience 4,000+ systems since 2006
Diagram showing a ground source heat pump moving heat from the house into the cooler ground in summer
How free cooling works

Your garden stays cool all summer. Your home can borrow that.

A correctly designed ground array can provide a cooler source than warm rooms in summer. The available cooling depends on the ground temperature and how the array has been used. Free cooling (engineers call it passive cooling) simply circulates fluid between your warm rooms and that cool ground.

The heat pump's compressor never starts — only the circulation pumps run — so free cooling uses very little electricity. Heat rejected in summer can help regenerate the ground array. The effect on winter performance depends on the array design and seasonal balance.

The same flat cross-section as the heating illustration, showing the summer mode of the same system. Two boreholes run deep into bedrock - typically 100 to 150 metres - drawn at true scale near the surface and near the toe, with a labelled break where most of the depth is not drawn. The sealed ground loop now leaves the heat pump carrying warmth from the house, goes DOWN one side of each borehole where short arrows show that warmth passing out into the rock, and comes back up cooler. Inside the house the underfloor circuit sends cool water out to the floor and receives it back warmer, so the colours of the two pipes are the reverse of the heating picture: colour follows the water's temperature. The radiator branch is drawn grey and still, because radiators cannot cool. The hot-water cylinder and its coil are drawn in the hot-water colour but dashed and without moving speckles, because the cylinder is still heated by this machine all summer - the machine simply pauses cooling and runs its compressor for a while to do it, rather than doing both at once. During cooling itself the compressor is off and only the two circulation pumps run. The three circuits still never mix.

Scroll the picture sideways to see all of it. Every label is written out below.

How a ground-source heat pump cools the same house in summer - passive cooling

What is in the picture

  • Ground loop: warmed fluid down the boreholes, cooled fluid back Borehole, drilled and grouted; Header trench back to the house; A single loop of pipe goes down and comes back; The loop turns round at the bottom; Cooler fluid going back down; Warmed fluid coming up
  • Floor circuit: cool water out to the floor, warmer water back Underfloor manifold; Hot-water cylinder; Heating coil - heating water never mixes with your tap water; Underfloor heating in the screed; Radiator; Warm water out; Cooler water back
  • Electricity from the grid, running the pumps Electricity from the grid; Fuse board
  • Tap water, kept completely separate from the heating water Your shower and taps; Cold water mains
  • Refrigerant sealed inside the heat pump, resting

The four steps inside the heat pump

  1. 1 Collect evaporator Environmental energy warms the refrigerant until it boils. It leaves as a warm gas at low pressure.
  2. 2 Squeeze compressor Electricity drives the compressor, squeezing that gas into a much smaller space. It leaves hot and at high pressure.
  3. 3 Release condenser The hot gas hands its heat to your heating water and condenses. It leaves as a hot liquid, still at high pressure.
  4. 4 Reset expansion valve A valve drops the pressure and the liquid flashes cold. It leaves as a cold mist, ready to collect more.
The same flat cross-section as the air-source heating illustration, showing the summer mode of the same machine. A reversing valve inside the outdoor unit swaps the roles of its two heat exchangers, so the plate exchanger against the heating water becomes the evaporator and the finned coil outside becomes the condenser. Warmth is taken out of the underfloor circuit - short orange arrows show it leaving the rooms and passing down into the screed - carried through the sealed refrigerant circuit, which is running at full speed with the compressor turning, and pushed out across the finned coil into the outside air. The air still travels the same way, in at the top of the coil and out low across the lawn away from the house, but it now arrives as the paler, cooler blue and leaves as the darker, warmer one, because colour follows temperature. The two heating pipes swap tones for the same reason: the pipe leaving the machine is now the cooler of the pair. The radiator branch and the hot-water cylinder coil are drawn grey and still, because radiators cannot cool. Electricity is drawn at full strength, because active cooling of this kind really does cost electricity to run.

Scroll the picture sideways to see all of it. Every label is written out below.

How an air-source heat pump cools the same house in summer

What is in the picture

  • Floor circuit: cool water out to the floor, warmer water back Insulated pipes through the wall; Hot-water cylinder; Heating coil - heating water never mixes with your tap water; Underfloor heating in the screed; Underfloor manifold; Radiator; Warm water out; Cooler water back
  • Electricity from the grid, running the compressor Electricity meter; Fuse board; Electricity from the grid
  • Tap water, kept completely separate from the heating water Your shower and taps; Cold water mains
  • Outdoor air: in at the coil cooler, out again a few degrees warmer Outdoor air is drawn in here; The same air is blown out here, a few degrees cooler; Finned coil - the air gives up its warmth here
  • Refrigerant sealed inside the outdoor unit, running in reverse

The four steps inside the heat pump

  1. 1 Collect evaporator Environmental energy warms the refrigerant until it boils. It leaves as a warm gas at low pressure.
  2. 2 Squeeze compressor Electricity drives the compressor, squeezing that gas into a much smaller space. It leaves hot and at high pressure.
  3. 3 Release condenser The hot gas hands its heat to your heating water and condenses. It leaves as a hot liquid, still at high pressure.
  4. 4 Reset expansion valve A valve drops the pressure and the liquid flashes cold. It leaves as a cold mist, ready to collect more.
Two ways to cool

Free cooling for most summers. Active cooling for hot ones.

Neither is "better" — it depends on how warm your home actually gets. We'll tell you honestly which fits.

Free cooling

Gentle, near-silent cooling that takes the edge off warm rooms — like the house staying comfortable on a day everyone else is complaining about.

  • Only the circulation pumps run, so it uses very little electricity
  • Best for homes that get warm, but not sweltering
  • Recharges the ground for more efficient winter heating
  • A simple addition to a ground source system

Active cooling

The heat pump runs in reverse and moves heat out of your home into the ground — proper air-conditioning-level cooling, held at the temperature you choose.

  • Holds a set temperature even on the hottest days
  • Comparable to conventional air conditioning
  • Uses the compressor as well as circulation pumps; electricity use depends on the cooling duty and system design
  • Sized against your ground array at the design stage
In your home

How the coolness reaches your rooms.

Cooling needs the right delivery — and we'd rather tell you the honest limits now than after the concrete is poured.

Underfloor heating, in reverse

Cool water through the same underfloor pipes gives gentle, even cooling across the whole floor. A dew-point controller manages the water temperature so the floor never drops below the condensation threshold — cool underfoot, never damp.

Fan coil units

Compact room units that blow air over a chilled coil — quicker, more controllable cooling for the rooms that need it most, like a bedroom under the roof.

What about radiators?

Radiators can't cool a room — they only work in one direction. If your system heats through radiators alone, cooling means adding fan coil units or underfloor pipework, and we'll tell you plainly whether that's worth it in your home.

Plan it early

Cooling is a design decision, not an add-on.

Not every heat pump has cooling capability built in. The right equipment, pipework and controls need to be in the design from the first drawing — so if you're building, extending or planning a heating upgrade, tell us about summer at the same time you tell us about winter.

Already have a ground source system? Cooling can sometimes be added later — it depends on your heat pump and how your home distributes heat. We'll assess it honestly rather than promise first and survey after.

Honest answers

The things homeowners ask about cooling.

Most modern ground source heat pumps can provide free cooling, and many also support active cooling — but it has to be specified when the system is designed, so the right equipment and controls are included. If cooling matters to you, say so at the first conversation and we'll design for it.

Free cooling is gentler — it takes several degrees off a warm house rather than chilling it, which is exactly what most Welsh summers need. Active cooling behaves like conventional air conditioning and holds the temperature you set. If your home overheats badly, active cooling is the honest recommendation.

No — radiators can't cool. Cooling needs underfloor pipework or fan coil units to carry the chilled water. Underfloor cooling also needs dew-point control so the floor surface never reaches the point where moisture would form — it's a solved problem, but it must be designed in, not bolted on.

Summer heat rejection can help regenerate the ground array after the heating season. How much that helps winter performance depends on the ground, collector design and seasonal balance; it is not a guaranteed efficiency gain.

Start with the ground

Ground source can provide passive or active cooling when specified for it. Suitable reversible air source models can also provide active cooling, with the right room units and controls. Ask us to check the model and design for your home.

Ground source heat pumps

Cooling a bigger building?

For commercial cooling — offices, schools, plant rooms and whole-building systems — we cover the technical detail on its own page.

Commercial cooling systems

Looked after, all year

One Comfort Care plan covers the system that heats and cools your home — annual service, monitoring and priority support.

Comfort Care plan

One system for warm winters and cool summers.

Tell us about your home — how it heats, and how warm it gets in July. We'll tell you honestly whether free cooling, active cooling or neither is the right fit.

Talk to our team Get a free estimate

No EPC? Send an enquiry or call 01269 833100. We can check the evidence needed for your property.

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