Underfloor Heating with Heat Pumps: The Ideal Combination
TLDR: Underfloor heating (UFH) is the ideal partner for heat pumps. It operates at 35-45°C flow temperatures where heat pumps are most efficient (COP 4.0+). Radiators often need 50-60°C, reducing efficiency to COP 2.5-3.0. UFH provides even heat distribution, frees wall space, and can reduce running costs by 15-30% compared to radiators. Installation costs £50-£120 per square metre depending on system type.
If there's one thing that separates good heat pump installations from great ones, it's the heat distribution system. And when it comes to getting the absolute maximum from your heat pump investment, nothing beats underfloor heating. The two technologies were practically designed for each other.
I've visited hundreds of homes with heat pumps over the years, and the pattern is unmistakable. Homeowners with underfloor heating consistently report lower bills, better comfort, and higher satisfaction than those relying on radiators alone. The physics explains why, but the real proof comes from people living with these systems day in, day out.
This guide covers everything you need to know about combining underfloor heating with heat pumps: the different system types, realistic costs, what installation involves, and stories from homeowners who've made the switch. Whether you're planning a new build, extending your home, or considering a major renovation, understanding UFH could be the key to unlocking your heat pump's full potential.
Why UFH and Heat Pumps Work Together
The relationship between flow temperature and heat pump efficiency is the single most important concept to understand. It explains why underfloor heating makes such a dramatic difference.
Heat pumps work by extracting heat from outside air (or ground) and concentrating it to a higher temperature. The higher the output temperature needs to be, the harder the compressor works, and the more electricity it consumes. This is measured as the Coefficient of Performance (COP)—the ratio of heat output to electrical input.
| Flow Temperature | Typical COP | Emitter System | What This Means |
|---|---|---|---|
| 35°C | 4.5-5.0 | UFH in well-insulated home | For every 1 kWh electricity, get 4.5-5 kWh heat |
| 40°C | 4.0-4.5 | UFH in average home | For every 1 kWh electricity, get 4-4.5 kWh heat |
| 45°C | 3.5-4.0 | UFH or large radiators | For every 1 kWh electricity, get 3.5-4 kWh heat |
| 55°C | 2.8-3.2 | Oversized radiators | For every 1 kWh electricity, get 2.8-3.2 kWh heat |
| 65°C | 2.2-2.6 | Standard radiators | For every 1 kWh electricity, get 2.2-2.6 kWh heat |
The difference is substantial. A heat pump running at COP 4.5 uses half the electricity of one running at COP 2.25 to produce the same amount of heat. Over a heating season, that's hundreds of pounds in savings.
Underfloor heating's large surface area means it can deliver adequate warmth at low flow temperatures—typically 35-45°C. Radiators, with their smaller surface area, need hotter water—typically 55-65°C—to output the same heat. This fundamental difference makes UFH the ideal partner for heat pumps.
Real Homeowner Experiences
Emma and Richard, Oxfordshire (1960s bungalow extension): "When we extended our bungalow in 2023, we knew we wanted a heat pump for the whole house. Our installer was clear: if we put UFH in the extension but kept the old radiators in the original part, the heat pump would have to run hotter to satisfy the radiators, which would reduce efficiency everywhere. So we bit the bullet and did UFH throughout—lifted all the floors in the original bungalow and installed low-profile UFH. It was disruptive, took three weeks, and cost about £14,000 just for the UFH. But combined with our 8 kW Vaillant heat pump (£12,500 minus the £7,500 BUS grant), our total heating costs are now about £850 per year. When we were on oil, we spent £2,400 annually. The payback on the whole project is looking like 7-8 years."
James, Manchester (new build, 2022): "We specifically chose a new-build developer who offered heat pumps as standard. Every room has underfloor heating—no radiators anywhere. The system runs at 35°C flow temperature, which our installer said gives us a COP of around 4.3. Our heating and hot water costs for a 140 square metre, 4-bed detached house are about £650 per year. Friends in similar-sized houses with gas boilers and radiators pay £1,200-£1,500. The only downside is response time—if you've let the house get cold, it takes a couple of hours to warm up. But we just run it continuously and let the thermostat manage temperature. Works perfectly."
Helen and David, Surrey (Victorian terrace, ground floor only): "Full UFH throughout our house wasn't practical—the upstairs floors couldn't take the added weight and height. So we compromised: UFH on the ground floor (kitchen, living room, dining room) and oversized radiators upstairs. Our installer configured the heat pump to run at 45°C, which works well for both. The ground floor is incredibly comfortable—warm feet on cold mornings, no cold spots. Upstairs works fine with the larger radiators. Total cost was about £8,500 for ground floor UFH plus £2,400 for three new oversized radiators upstairs. Our heat pump cost £11,000 minus the £7,500 grant. Running costs are about £1,050 per year compared to £1,800 on our old gas boiler."
Michael, Edinburgh (self-build): "Building our own house gave us complete control. We went with wet UFH on the ground floor (polished concrete screed—beautiful and efficient) and low-profile UFH upstairs on timber joists. The system runs at 32°C most of the year, rising to 38°C only in the coldest weather. Our 9 kW Mitsubishi heat pump achieves measured COP of 4.6 on average—we monitor it obsessively. Annual heating cost for 180 square metres is about £720. We're certified Passivhaus, which helps, but even accounting for our excellent insulation, the UFH makes a massive difference to efficiency."
Linda, Devon (1980s detached with conservatory): "Our conservatory was always freezing in winter despite a radiator. When we installed our heat pump, the installer suggested UFH just in the conservatory—a relatively small job since we were replacing the floor anyway. Cost about £1,800 for 25 square metres. The difference is remarkable. The conservatory is now usable year-round, and because UFH works so well with the heat pump, it barely affects our running costs. We've since added UFH to the kitchen during a renovation. Wish we'd done the whole house, but the disruption in occupied rooms is significant."
Types of Underfloor Heating
Wet/Water-Based UFH (Screed Systems)
Traditional wet UFH involves embedding pipes in a concrete screed, typically 65-75mm thick over insulation. This is the most common system in new builds and major renovations.
- How it works: Warm water from your heat pump circulates through a continuous loop of pipe, transferring heat to the screed, which then radiates upward into the room.
- Installation: Requires 100-150mm total build-up (insulation plus screed). Floor levels rise significantly.
- Response time: Slow to heat up (2-4 hours) but excellent thermal mass stores heat and evens out temperature fluctuations.
- Best for: New builds, extensions, ground floor renovations where floor levels can be adjusted.
- Cost: £50-£80 per square metre installed, including materials and labour.
The thermal mass of a screed system is both strength and weakness. It takes time to heat up, so these systems work best when run continuously at a steady temperature. The upside is exceptional stability—even if the heat pump switches off for maintenance, the floor stays warm for hours.
Low-Profile Systems (Retrofit)
Low-profile or "dry" UFH systems use thin panels with routed channels for pipes, typically adding just 15-25mm to floor height. These are designed specifically for retrofit installations.
- How it works: Pipes sit in pre-formed channels in aluminium-faced or foil-backed boards. The metal spreads heat quickly across the floor surface.
- Installation: Laid over existing subfloor. Minimal floor height gain. Often compatible with existing doors and trim.
- Response time: Faster than screed (30-60 minutes) due to lower thermal mass.
- Best for: Retrofit installations, rooms where floor height is constrained, projects where minimising disruption is priority.
- Cost: £80-£120 per square metre, higher than screed but less disruption.
Popular low-profile brands include Nu-Heat, Polypipe, and Warmup. Each has slightly different specifications, but all achieve similar results. Your installer should recommend a system based on your specific floor construction and heat loss requirements.
Electric UFH
Electric underfloor heating uses resistance cables or mats to generate heat directly. While popular for bathrooms and small areas, it's generally not suitable for integration with heat pumps.
- Why it doesn't work with heat pumps: Electric UFH is 100% efficient (1 kWh electricity = 1 kWh heat). A heat pump with wet UFH achieves 350-450% efficiency. Using electric UFH negates the whole point of having a heat pump.
- When it might make sense: Small areas like bathrooms where running pipes is impractical, or as occasional boost heating in specific rooms.
- Cost to run: About 3-4 times more expensive per kWh of heat than wet UFH connected to a heat pump.
If you're installing a heat pump, avoid electric UFH for any significant heated area. The running costs will be disappointing.
Detailed Costs
UFH costs vary considerably depending on system type, floor construction, and whether you're building new or retrofitting.
| System Type | Cost per sqm | 80 sqm Ground Floor | Notes |
|---|---|---|---|
| Screed system (new build) | £50-£80 | £4,000-£6,400 | Includes insulation, pipes, screed |
| Screed system (retrofit) | £70-£100 | £5,600-£8,000 | Add floor removal, skip hire |
| Low-profile retrofit | £80-£120 | £6,400-£9,600 | Minimal disruption |
| Floor covering replacement | £30-£60 | £2,400-£4,800 | If tiles/wood need replacing |
Additional costs to consider:
- Manifold and controls: £400-£800 depending on number of zones
- Mixing valve (if needed): £200-£400 to blend flow temperatures
- Smart thermostats: £150-£300 per zone for programmable control
- Moving out during work: Screed installations in occupied homes may require temporary accommodation
The Installation Process
New Build / Major Extension
Installing UFH during construction is straightforward and minimally disruptive:
- Design: Installer calculates heat loss per room and designs pipe layouts to deliver required output.
- Insulation: Rigid insulation boards laid over the subfloor (typically 50-100mm EPS or PIR).
- Pipes: UFH pipes clipped to the insulation in designed pattern (typically 100-200mm spacing).
- Manifold: Pipes connected to manifold, usually located in utility room or airing cupboard.
- Pressure test: System filled and tested before screed poured.
- Screed: 65-75mm liquid or traditional screed poured over pipes.
- Curing: Screed must cure for 4-6 weeks before floor covering installed.
- Commissioning: System gradually brought up to operating temperature over several days.
Timeline: Allow 2-3 days for UFH installation, plus curing time before floor finishing.
Retrofit Installation
Retrofitting UFH in an existing home is more complex:
- Survey: Installer assesses existing floor construction, levels, and heat loss.
- Preparation: Existing floor covering removed. Subfloor checked and levelled if necessary.
- Insulation (if space allows): Thin insulation laid if floor height permits.
- UFH panels: Low-profile panels laid with pipes in channels.
- Connection: Pipes connected to new or existing manifold.
- Pressure test: System tested before finishing.
- Floor covering: New floor installed—typically engineered wood or tiles.
- Commissioning: System brought up to temperature gradually.
Timeline: Allow 3-5 days per room, depending on floor type and complexity.
Floor Coverings: What Works Best
Not all floor coverings conduct heat equally. Your choice affects UFH performance:
| Floor Type | Thermal Conductivity | UFH Suitability | Notes |
|---|---|---|---|
| Porcelain/ceramic tile | Excellent | Ideal | Best heat transfer, feels warm quickly |
| Natural stone | Excellent | Ideal | Beautiful and efficient |
| Polished concrete | Excellent | Ideal | No floor covering needed |
| Engineered wood | Good | Very suitable | Thinner boards better. Max 18mm. |
| Solid wood | Moderate | Caution needed | Can warp. Needs acclimatisation. |
| Vinyl/LVT | Good | Very suitable | Check manufacturer rating for UFH |
| Thin carpet | Moderate | Acceptable | Tog rating under 1.5 tog total |
| Thick carpet | Poor | Not recommended | Insulates floor, blocks heat |
General rule: anything with a combined tog rating (carpet plus underlay) above 1.5 tog will significantly reduce UFH effectiveness. If you want carpet, choose thin, low-tog options with minimal underlay.
Q&A: UFH and Heat Pumps
Q: Is UFH essential for heat pumps?
A: No, heat pumps work with radiators—millions of UK homes prove this. But you may need larger radiators and will accept lower efficiency. UFH optimises the system, potentially reducing running costs by 15-30% compared to radiators. It's not essential, but it's the best option if you can manage the installation.
Q: Can I retrofit UFH in an existing home?
A: Yes, but it's disruptive. Low-profile systems minimise floor height gain (15-25mm). Many homeowners retrofit room-by-room during renovations rather than all at once. Ground floors are easier than upper floors due to structural considerations.
Q: How quickly does UFH heat up?
A: Slower than radiators. Screed systems take 2-4 hours to reach temperature from cold; low-profile systems are faster at 30-60 minutes. The solution is running UFH continuously at consistent temperature rather than on/off. Modern controls handle this automatically.
Q: What floor coverings work best?
A: Tile, stone, and polished concrete are ideal (high thermal conductivity). Engineered wood works well. Thick carpet or underlay reduces efficiency significantly—if you want carpet, choose thin options with tog rating under 1.5 total.
Q: Can I mix UFH and radiators in the same house?
A: Yes, this is common. Ground floor UFH with radiators upstairs works well. The heat pump runs at a moderate flow temperature (45-50°C) that satisfies both systems reasonably. Some installers use a mixing valve to supply lower-temperature water to UFH zones while radiators get hotter water—but this adds complexity and cost.
Q: What about maintenance?
A: Wet UFH systems have very few moving parts. The pipes are designed to last 50+ years—longer than the building in most cases. Manifolds may need occasional servicing. The main maintenance is inhibitor checks (same as any wet heating system) and occasional manifold actuator replacement if zones stop working.
The Bottom Line
Underfloor heating is the ideal emitter for heat pumps. The combination maximises efficiency, delivers exceptional comfort, and reduces running costs significantly compared to radiator-based systems.
For new builds, extensions, and major renovations, UFH is worth the investment. The additional cost (typically £5,000-£12,000 for a typical home) pays back through lower running costs over 7-12 years, then continues saving money for the life of the system.
For retrofits where full UFH isn't practical, consider a hybrid approach: UFH on ground floors where floor replacement is easier, oversized radiators upstairs. Even partial UFH improves overall system efficiency.
The combination of a properly sized heat pump, the £7,500 BUS grant, and underfloor heating creates a heating system that's comfortable, efficient, and genuinely cheaper to run than gas or oil. It's not the cheapest option upfront, but it's often the smartest long-term investment for your home's heating.