Home Heat Pump Guide

Air Source Heat Pump and Underfloor Heating: The Perfect Match

If you are planning to install an air source heat pump, one of the best decisions you can make is pairing it with underfloor heating. The two technologies complement each other so well that many in the industry consider them the ideal combination for home heating.

The reason is simple: underfloor heating works at low water temperatures — exactly the conditions where heat pumps operate most efficiently. The result is lower electricity bills, more even heat distribution, and a more comfortable home.

This guide explains why the pairing works so well, what the retrofit options are for existing homes, and what it all costs.

Why Underfloor Heating and Heat Pumps Work So Well Together

Low Flow Temperatures = High Efficiency

This is the fundamental reason the pairing works. Underfloor heating operates at flow temperatures of 30-40°C — far lower than the 50-70°C required by conventional radiators. At these low flow temperatures, an air source heat pump achieves its highest efficiency.

The numbers tell the story. A heat pump running at 35°C flow temperature (typical for UFH) achieves a seasonal COP of 3.5-4.0 or higher. The same heat pump running at 50°C (typical for standard radiators) achieves a seasonal COP of 2.5-3.0. That efficiency difference translates directly into lower electricity bills — potentially 20-30% less than a radiator-based system.

Large Heat Emitter Surface Area

Underfloor heating turns the entire floor into a heat emitter. Even at low water temperatures, the sheer surface area means plenty of heat is delivered to the room. This is why UFH can keep rooms warm at 35°C flow temperature while a radiator at the same temperature would feel barely lukewarm.

Even Heat Distribution

With radiators, heat rises from a point source, creating warm zones near the radiator and cooler zones elsewhere. Underfloor heating distributes heat evenly across the entire floor. The result is more consistent comfort, fewer cold spots, and heat exactly where you want it — at floor and body level rather than pooling at the ceiling.

No Radiators Taking Up Wall Space

A practical benefit rather than an efficiency one, but worth mentioning. Removing radiators frees up wall space for furniture, storage, and aesthetics. In smaller rooms, this can make a noticeable difference to how the space feels and functions.

Types of Underfloor Heating

There are two main types, and only one works with a heat pump.

Wet (Water-Based) Underfloor Heating

This is the type that pairs with a heat pump. Warm water from the heat pump circulates through a network of plastic pipes buried in or beneath the floor. The pipes are typically laid in loops, spaced 100-200mm apart, covering the entire floor area of each room.

Wet UFH is the standard choice for new builds and major renovations. It is efficient, effective, and connects directly to the heat pump's heating circuit — just like radiators would.

Electric Underfloor Heating

Electric UFH uses thin heating cables or mats embedded in the floor. It runs on direct electricity (COP of 1.0) and cannot be connected to a heat pump. It is fine for small areas like bathrooms where running wet UFH pipework is impractical, but it is not a substitute for a whole-house wet UFH system paired with a heat pump.

Retrofit Options for Existing Homes

Installing underfloor heating in a new build is straightforward — the UFH goes in during construction. Retrofitting into an existing home is more complex but absolutely possible.

Option 1: Screed System (Ground Floor, Major Renovation)

The traditional approach: UFH pipes are laid on insulation boards and covered with a liquid screed or sand-cement screed, typically 50-75mm deep. This is the most effective system but requires raising the floor level significantly.

  • Best for: Ground floors during a major renovation where the existing floor is being replaced anyway
  • Floor height increase: 80-120mm (including insulation)
  • Cost: £50-£80 per square metre (excluding floor finish)
  • Performance: Excellent — high thermal mass provides even, stable heat

Option 2: Low-Profile Overlay System (Retrofit Without Major Works)

Low-profile UFH systems are designed specifically for retrofit. They use thin panels (12-25mm) with pre-formed channels for the heating pipes, laid directly on top of the existing floor. The new floor finish goes on top.

  • Best for: Retrofit in occupied homes where minimising disruption is important
  • Floor height increase: 15-30mm (including panels and pipe)
  • Cost: £60-£100 per square metre (excluding floor finish)
  • Performance: Good — lower thermal mass means faster response but slightly less even heat distribution than screed systems

Low-profile systems are the most popular retrofit option. They work well on ground floors and upper floors, and the modest floor height increase can usually be accommodated with minor adjustments to door heights and thresholds.

Option 3: Between-Joist System (Suspended Timber Floors)

For homes with suspended timber floors (common in Victorian and Edwardian houses), UFH pipes can be installed between the joists from below — if there is a crawl space — or from above by lifting the floorboards.

  • Best for: Period properties with suspended timber floors and access from below
  • Floor height increase: None (pipes sit between existing joists)
  • Cost: £40-£70 per square metre
  • Performance: Moderate — timber is a natural insulator, so heat transfer through the floor is slower. Aluminium spreader plates between the joists improve performance significantly

Which Rooms Should Have Underfloor Heating?

You do not necessarily need UFH in every room. A common and cost-effective approach is to install UFH in the rooms where it makes the most difference and use radiators (or keep existing radiators) elsewhere.

Priority Rooms for UFH

  • Living room: The main living space benefits most from even floor-level warmth
  • Kitchen/dining area: Often the largest open space, frequently with hard floors that feel cold without UFH
  • Bathroom: Warm floors are a luxury, and the moisture resistance of tile over UFH is a bonus
  • Open-plan areas: Large open spaces are ideal for UFH — even heat across the whole area with no radiators interrupting the layout

Rooms Where Radiators May Be Fine

  • Bedrooms: Occupants are usually under a duvet, and heat demand is lower. Radiators work fine here, especially if oversized to work at lower flow temperatures
  • Hallways and landings: These benefit from UFH, but radiators can work adequately in these smaller spaces
  • Utility rooms and cloakrooms: Low priority — radiators or even towel rails are usually sufficient

A mixed system — UFH downstairs, radiators upstairs — is a popular and practical approach that balances performance with cost. The heat pump supplies both circuits, with a mixing valve or the heat pump's built-in zone control managing the different flow temperatures.

For guidance on using radiators with a heat pump, see our guide on whether you need new radiators for a heat pump.

Costs: UFH with a Heat Pump

Here is what you can expect to pay for underfloor heating as part of a heat pump installation:

New Build or Major Renovation (Screed System)

  • UFH materials and installation: £50-£80 per m²
  • Typical three-bedroom house (60m² of UFH): £3,000-£4,800
  • Manifold, controls, and connection to heat pump: £500-£1,000
  • Total UFH cost: £3,500-£5,800

Retrofit (Low-Profile Overlay System)

  • UFH materials and installation: £60-£100 per m²
  • Typical ground floor retrofit (40m² of UFH): £2,400-£4,000
  • Manifold, controls, and connection: £500-£1,000
  • New floor finish (if replacing): Variable
  • Total UFH cost: £2,900-£5,000

Is UFH Worth the Extra Cost?

Compared to a radiator-only system, adding UFH costs an additional £2,000-£5,000 for a typical house. However, the improved heat pump efficiency saves £100-£250 per year in electricity. Over a 20-year heat pump lifespan, that is £2,000-£5,000 in energy savings — roughly covering the additional cost. Add in the comfort and aesthetic benefits, and UFH usually makes financial sense.

Floor Finishes and Their Impact

The floor finish above the UFH affects how well heat transfers into the room. Some finishes conduct heat better than others.

Best Finishes for UFH

  • Stone and ceramic tiles: Excellent heat conductors. They warm up quickly and feel pleasantly warm underfoot. The best choice for UFH performance
  • Engineered wood: Good heat conductor, provided it is rated for use with UFH (most engineered wood flooring is). Solid wood is not recommended as it can warp with the heat cycling
  • Luxury vinyl tile (LVT): Good heat transfer and rated for UFH use. A popular and practical choice
  • Polished concrete: Excellent — high thermal mass stores heat and releases it gradually

Less Ideal Finishes

  • Thick carpet and underlay: Acts as an insulator, reducing heat transfer into the room. UFH can still work under carpet, but you may need a slightly higher flow temperature, which reduces heat pump efficiency. Use a thin, UFH-rated underlay if carpet is essential
  • Solid hardwood: Risk of warping and gaps as the wood expands and contracts. Engineered wood is a much better alternative

Response Time and Thermal Mass

One difference between UFH and radiators that new users notice is the response time. Underfloor heating takes longer to warm up and cool down than radiators — especially screed-based systems with high thermal mass.

A screed UFH system might take 2-4 hours to bring a room up to temperature from cold, compared to 30-60 minutes for radiators. This is not a problem if the system runs continuously (as heat pumps prefer), but it does mean you cannot quickly boost the temperature for a short period.

Low-profile overlay systems have lower thermal mass and respond faster — typically 30-90 minutes — making them more responsive for retrofit situations where occupancy patterns vary.

The key principle: run UFH on a steady schedule, ideally controlled by the heat pump's weather compensation, rather than switching it on and off like a gas boiler with radiators.

Controls and Zoning

Modern UFH systems offer excellent room-by-room temperature control through individual zone thermostats and motorised manifold actuators. Each room (or zone) has its own thermostat that controls the flow of warm water to that zone's loop.

This means you can heat the living room to 21°C, the bedroom to 18°C, and the spare room to 16°C — all independently. This level of control reduces energy waste and is one of the practical advantages of UFH over a traditional radiator system with a single room thermostat.

Smart thermostats compatible with UFH (such as Heatmiser Neo, Wunda, or Polypipe) allow remote control via smartphone apps and can learn your schedule to optimise heating times.

Common Questions About UFH and Heat Pumps

Can I retrofit UFH upstairs?

Yes, but it is more disruptive than ground-floor retrofit. The floorboards or floor panels need to be lifted to install the pipes between joists or to lay an overlay system. Low-profile systems add less height but may still require door trimming. Many homeowners choose UFH downstairs and radiators upstairs as a practical compromise.

Can I have UFH and radiators on the same heat pump?

Yes, and this is very common. The heat pump supplies both circuits, with a mixing valve reducing the water temperature for the UFH circuit (which needs 30-40°C) while the radiator circuit runs at a slightly higher temperature (40-50°C). Most heat pump controllers have built-in two-zone capability for exactly this scenario.

Does UFH work with all floor types?

UFH works with most floor types — concrete, screed, timber, and overlay systems. The floor finish above needs to be UFH-compatible (tiles, engineered wood, LVT, or thin carpet with UFH-rated underlay). Your UFH supplier will advise on compatibility with your chosen floor finish.

How long does UFH last?

The pipes used in wet UFH systems (typically PEX or PERT plastic) have a design life of 50 years or more. The manifold, actuators, and controls may need replacing after 15-20 years, but the pipes themselves should last the lifetime of the building. This means when the heat pump is eventually replaced, the UFH system can carry on with the new unit.

Is UFH suitable for older houses?

Yes, with the right approach. Between-joist systems work well in period properties with suspended timber floors. Low-profile overlay systems can work on solid ground floors. The key is choosing the right system type for the existing floor construction. For more on heat pumps in older properties, read our guide to air source heat pumps.

Will I need building regulations approval for UFH?

Installing UFH as part of a heat pump system is covered under the heat pump's Building Regulations notification (done by your MCS-certified installer). If the UFH installation involves structural changes (such as lowering a floor to accommodate a screed system), separate Building Regulations approval may be needed. Your installer will advise.