Underfloor Heating and Heat Pumps: The Ideal Pairing Explained

Underfloor heating and air source heat pumps are considered the ideal pairing for good reason: UFH runs at flow temperatures of 35–40°C, which is exactly the range where air source heat pumps operate at their highest efficiency. Combine the two and you can achieve SCOP values of 4.0 or higher — significantly better than the same heat pump driving conventional radiators. Here is what you need to know about costs, compatibility, and retrofit options.

Why underfloor heating works so well with heat pumps

All heating systems transfer heat to a room through a distribution surface — radiators, underfloor pipes, or fan coil units. The larger the surface area, the lower the temperature needed to deliver the same amount of heat. Underfloor heating uses the entire floor as the emitter, giving it a vastly larger surface area than wall-mounted radiators. This lets it deliver comfortable heat at 35–40°C flow temperature rather than the 65–75°C required by older, smaller radiators.

For a heat pump, lower flow temperature means less work compressing refrigerant across a large temperature gap — and therefore higher efficiency. The relationship is roughly linear: every 1°C reduction in flow temperature improves COP by approximately 2–3%. Going from 55°C to 35°C can improve efficiency by 40–60%, which translates directly into lower electricity bills.

Wet vs dry underfloor heating systems

There are two types of underfloor heating: wet (hydronic) systems that circulate warm water through pipes embedded in or under the floor, and dry (electric mat) systems that use resistance heating cables. Only wet UFH is relevant for heat pump pairing — electric UFH mats are effectively just another form of direct electric heating with no efficiency advantage.

Wet UFH can be installed in two configurations. Screed systems embed the pipes in a concrete or anhydrite screed layer — these are standard for new builds and major renovations. Low-profile systems (also called overlay or floating systems) sit above the existing floor structure using specially designed panels, adding only 15–25mm to floor height — suitable for retrofits where floor height is a constraint.

UFH installation costs

For a typical 3-bedroom home with 80m² of ground floor area, wet UFH installation costs range from £4,000 to £9,000 installed, including manifolds and controls. This is in addition to the heat pump installation itself but is often bundled by specialist installers.

Can underfloor heating be retrofitted?

Retrofit is possible but requires careful assessment. The main challenges are floor height (low-profile systems add 15–25mm, which can affect doors, skirting boards, and transitions to adjacent rooms), floor type (some floor finishes respond poorly to heating — solid wood can warp, thick carpet insulates too well), and whether existing screed needs breaking up.

Solid concrete ground floors are the easiest retrofit candidates — a low-profile overlay system can be laid directly on clean concrete with minimal disruption. Suspended timber floors require either a staple-up approach (pipes clipped beneath the floorboards from below, accessed from a basement or crawl space) or lifting and relaying the floorboards to install pipes above the joists.

Many retrofit heat pump installations use a pragmatic mix: UFH in the ground floor rooms where it is easiest to install, and upsized radiators upstairs where UFH would be more disruptive. This hybrid approach can still achieve very good overall efficiency.

UFH vs upsized radiators with a heat pump

If a full UFH installation is not practical, upsized radiators are the next best option. Modern large-format radiators (double panel, large surface area) can be sized to deliver adequate heat output at 45–50°C flow temperature, achieving SCOP values in the 3.2–3.8 range. This is less efficient than UFH but far better than running an undersized radiator system at 55–60°C.

Your installer should calculate the required radiator size for each room at the target flow temperature — a process called a heat emitter sizing calculation. Rooms with south-facing glazing or good insulation may need only modest radiator upgrades; north-facing, poorly insulated rooms may need complete replacement.

Floor finish compatibility

Not all floor finishes work equally well with underfloor heating. The best performers are stone, ceramic or porcelain tiles (excellent conductors), and engineered wood (stable and efficient). Solid hardwood is acceptable if properly acclimatised and installed with a maximum heating temperature limit. Thick carpet (tog rating above 1.5) significantly reduces heat output and is generally not recommended. Laminate flooring is usually fine if rated for use with UFH.