For context on how this infrastructure fits within wider decarbonisation policy, see our explanation of the UK Warm Homes Plan and what it means for low-carbon heating.
Under the Warm Homes Plan, shared ground loop systems and ambient heat networks are expected to expand significantly across urban estates and new developments. These systems collect ambient ground energy to feed heat pumps, providing low-carbon heating at scale.
The most common approach uses vertical boreholes drilled to depths of 100 to 200 metres. This method is proven and widely deployed. However, as discussed in our analysis of why borehole drilling is becoming a bottleneck in heat network delivery, deep vertical drilling introduces constraints in urban environments and occupied social housing estates.
Surface thermal energy systems represent a fundamentally different approach. Rather than extracting heat from deep ground strata through vertical boreholes, these systems use the building's surface areas as both a thermal collector and storage medium. Pipework installed just 50mm beneath resin-bound paving creates a bidirectional thermal system that works year-round.
This article explains how surface thermal energy systems work, how they compare to conventional borehole systems, and where they fit within low-carbon heating infrastructure.
How Surface Thermal Energy Systems Work
Surface thermal energy systems install closed-loop pipework networks 50mm beneath resin-bound paving. This shallow installation creates a reactive thermal surface that collects ambient energy from multiple sources and can provide both heating and ice prevention functions.
Year-round heating operation:
The system collects thermal energy from three sources to provide space heating and hot water throughout the year. Solar radiation warms the resin-bound surface, and this heat conducts into the ground layers where the pipework sits. Ambient air temperature affects the shallow ground mass, creating thermal exchange between surface and subsurface. The ground itself acts as a stable thermal store, maintaining residual heat even during winter months.
Fluid circulates through the buried pipework, absorbing this thermal energy from the surrounding ground. The warmed fluid returns to a heat pump that upgrades the collected heat to temperatures suitable for space heating and domestic hot water. The system achieves Seasonal Coefficient of Performance (SCOP) values above 4, providing efficient low-carbon heating year-round.
The shallow installation depth allows the system to benefit from all three thermal sources simultaneously. Unlike deep boreholes that rely solely on stable deep ground temperatures, or solar thermal panels that depend only on direct sunlight, surface thermal systems harvest energy from whichever source is most abundant at any given time.
Winter ice prevention:
When surface temperatures drop to 0°C, the system can activate ice prevention mode. Waste heat from the building, which would normally be rejected to atmosphere during heat pump operation, circulates through the surface pipework. This maintains the surface above freezing, eliminating the need for salting, gritting or snow clearance on pathways, car parks and access routes.
This ice prevention function uses heat that already exists in the system rather than generating new heat. The waste heat that would otherwise vent to atmosphere instead provides a useful function while simultaneously creating a shallow thermal store that the system can draw from later.
Summer enhanced operation:
In warmer months, the resin-bound surface absorbs significantly more solar radiation, heating the paving material and the ground beneath. The system harvests this enhanced thermal energy, providing pre-heated water to the heat pump. During peak summer periods, collected surface temperatures can reach levels that require minimal heat pump uplift to achieve domestic hot water temperatures (up to 50°C), significantly improving system efficiency.
Thermal storage and system integration:
The system can integrate with thermal batteries that store excess heat collected during peak solar periods for use during evenings or lower-demand times. This storage capacity allows the surface to function as a thermal battery, capturing energy when abundant and releasing it when needed.
Integration with conventional solar PV further enhances system efficiency. Solar electricity can power the circulation pumps and heat pump, while the surface thermal system provides the thermal energy for heating. The combination creates a complementary renewable energy system where electrical and thermal generation work together.
Surface Systems Compared to Borehole Ground Source Heat Pumps
Both surface thermal systems and borehole ground source heat pumps achieve Seasonal Coefficient of Performance (SCOP) values above 4, placing them in the same performance category for low-carbon heating. The engineering difference lies in how and where thermal energy is collected, and what additional functions the system provides.
Depth and installation:
Borehole systems drill vertically to 100-200 metres, requiring specialist drilling contractors, heavy rigs and extended site occupation. Installation is disruptive but self-contained. Once complete, the boreholes are permanent and largely maintenance-free.
Surface thermal systems install pipework 50mm below resin-bound surfacing during ground preparation or resurfacing works. The installation integrates with scheduled maintenance rather than requiring separate specialist mobilisation. The pipework is embedded within the substrate as the surface is constructed or renewed, leaving no visible infrastructure above ground.
Thermal source and seasonal operation:
Borehole systems access stable deep ground temperatures that vary minimally throughout the year. This consistency provides predictable thermal input year-round, with the same basic operating principle in all seasons.
Surface thermal systems operate differently in winter and summer. Winter operation uses waste heat from the building to maintain ice-free surfaces while creating a shallow thermal store. Summer operation harvests solar energy absorbed by the resin-bound paving material. The system switches function seasonally, adapting to ambient conditions and building requirements.
Dual functionality:
Borehole systems serve one function: providing thermal energy for space heating and hot water via a heat pump.
Surface thermal systems serve two functions simultaneously:
- Providing thermal energy for heating and hot water (via heat pump, SCOP >4)
- Maintaining ice and snow-free external surfaces without chemical de-icing
This dual functionality is particularly relevant for sites where winter accessibility and safety matter. Hospitals, schools, care homes, transport hubs and public buildings benefit from guaranteed ice-free access alongside low-carbon heating.
Site impact and programme delivery:
As discussed in our article on low-disruption heating upgrades for social housing, borehole drilling in occupied estates requires prolonged site occupation, car park closures and extended contractor access. Surface thermal installation aligns with resurfacing schedules that would proceed regardless, reducing incremental disruption and programme complexity.
For housing associations planning car park renewals or councils managing estate improvement programmes, thermal infrastructure can be integrated without additional resident impact beyond the scheduled works.
Performance and efficiency:
Both system types achieve comparable seasonal performance when properly designed. Borehole systems benefit from stable thermal input. Surface systems benefit from high solar gain in summer and waste heat utilisation in winter. The >4 SCOP achieved by both approaches places them among the most efficient low-carbon heating technologies available.
Integration with Heat Pumps and Thermal Storage
The heat pump manages bidirectional operation. In heating mode, it draws thermal energy from the surface collectors and upgrades it for space heating and hot water. In ice prevention mode, it directs building waste heat into the surface pipework to maintain frost-free conditions.
Thermal battery integration allows excess summer heat to be stored for later use. When surface temperatures peak during midday, the system can divert collected energy to thermal storage rather than immediately using it. This stored heat supplies evening or morning hot water demand, reducing peak electrical load and maximising use of collected solar energy.
The system also integrates with ambient temperature heat networks. In shared loop applications, the surface thermal collectors maintain a low-temperature distribution network that circulates to multiple properties. Each property extracts the heat it needs via individual heat pumps, while sharing the thermal collection infrastructure across the development.
Delivery and Programme Considerations
The installation process differs significantly from borehole systems, creating different programme implications.
Borehole installation is a discrete project phase. Drilling contractors mobilise, complete the work, demobilise. The timeline depends on ground conditions, number of boreholes and site access. For retrofit projects, this means dedicated disruption periods that residents must accommodate.
Surface thermal installation integrates with surfacing works. If a car park requires resurfacing, the thermal pipework is installed during the base preparation before the final resin-bound paving layer. If new pathways are being constructed, the thermal loops are embedded during groundworks. The thermal infrastructure becomes part of scheduled works rather than a separate project.
This integration offers several programme advantages:
For new developments, thermal infrastructure can be incorporated into ground preparation without extending construction timelines. The pipework is installed as part of the external works package.
For retrofit projects, alignment with planned resurfacing removes the need for separate contractor mobilisation. Housing associations and councils already schedule car park renewals and pathway maintenance. Thermal infrastructure becomes an enhancement to planned works rather than an additional disruption event.
For projects with tight funding windows, integration with scheduled works reduces programme risk. There is no dependency on drilling contractor availability or ground condition complications that could delay specialist works.
Where Surface Thermal Systems Are Appropriate
Surface thermal energy systems work best in specific contexts. Understanding where they add value, and where conventional boreholes may be more suitable, is essential for correct system selection.
Sites well-suited to surface thermal systems:
Developments with substantial car parking, courtyards or external hard surfacing where available surface area can accommodate the required thermal pipework without compromising parking capacity or accessibility.
Projects where ice and snow-free surfaces provide operational benefit beyond energy efficiency, such as hospitals, care facilities, schools, transport hubs and public access buildings.
Retrofit schemes where resurfacing or ground improvement works are already scheduled, allowing thermal infrastructure to be integrated without additional disruption.
Urban or constrained sites where deep borehole drilling presents access challenges, prolonged disruption or planning complications.
Sites where visual impact matters, and roof-mounted solar thermal collectors would be inappropriate for planning or aesthetic reasons.
Sites where boreholes may be more appropriate:
Developments with minimal external hard surfacing where vertical boreholes make better use of limited land area.
Sites with excellent drilling access and ground conditions where borehole installation can proceed efficiently without disruption to occupied areas.
Greenfield sites where no existing surfacing requires renewal and drilling can proceed without affecting occupied buildings.
The engineering assessment must consider available surface area, thermal demand, site constraints, planned maintenance schedules and whether ice prevention provides additional value beyond heating efficiency. Surface thermal systems are a design option where site conditions and operational requirements align, not a universal replacement for boreholes.
Infrastructure Choice Under the Warm Homes Plan
The Warm Homes Plan mandates decarbonisation of heating at scale. It does not mandate a specific thermal collection method. The policy objective is achieving low-carbon heat delivery efficiently and reliably across diverse building types and site conditions.
As heat network zoning begins in 2026 and shared ground loop systems expand across urban estates, the range of viable collection technologies will affect programme delivery. Both borehole and surface thermal systems achieve the >4 SCOP performance required for effective low-carbon heating. The choice depends on site characteristics, programme constraints and operational requirements.
Infrastructure flexibility means selecting the approach that delivers required thermal performance within the constraints of site layout, available land, programme timelines and occupant impact. It does not mean technical compromise or settling for lower performance.
Surface thermal energy systems add a viable collection method for contexts where:
- Substantial hard surfacing exists or is being renewed
- Ice prevention provides operational benefit
- Drilling access or disruption presents programme risks
- Integration with scheduled works reduces delivery complexity
Where deep boreholes suit the site and programme requirements, they should be specified. Where surface systems align better with site conditions and delivery constraints, they offer comparable thermal performance with different installation characteristics and dual functionality.
The challenge remains execution. Policy sets targets, funding provides capital, but programme success depends on matching technology to real-world contexts. That requires engineering assessment of each site's specific conditions, not universal application of a single solution regardless of suitability.
As deployment scales under national decarbonisation programmes, diversified infrastructure approaches reduce programme risk. Sites get the system that fits their constraints while achieving the same performance outcomes. The variety in collection methods supports wider adoption by removing barriers that would otherwise make some sites unsuitable for low-carbon heating infrastructure.