HeatPumpUnderfloor Heating with a Heat Pump
Underfloor heating (UFH) is the ideal heat emitter for a heat pump. It runs at low flow temperatures, spreads heat evenly across the room, and frees up wall space. You don't need it — radiators work too — but if you're renovating anyway, UFH is worth serious consideration.
Why Underfloor Heating Suits Heat Pumps
Heat pumps are most efficient at low flow temperatures. The lower the temperature of water in the system, the less electricity the heat pump uses. Underfloor heating works brilliantly at 25–35°C flow temperature — compared to 35–45°C for oversized radiators and 55–75°C for a gas boiler.
At 30°C flow, a heat pump achieves a COP of 4.0 or higher — meaning 4 units of heat for every 1 unit of electricity. At 45°C (for radiators), COP drops to around 3.0. That efficiency difference translates to 15–25% lower running costs with underfloor heating compared to radiators.
Retrofit Options
In-Screed Systems (£40–£60/m²)
Pipes are laid on insulation boards and covered with a new screed layer (50–75mm deep). This is the most effective system — the thermal mass of the screed stores heat and releases it slowly, providing very even warmth. However, it raises the floor height significantly and involves more disruption. Best suited to ground-floor renovations where you're already replacing the floor.
Overlay / Low-Profile Systems (£60–£80/m²)
Designed specifically for retrofit. Pre-routed insulation panels (15–25mm thick) sit on top of the existing floor, with pipes clipped into channels. The finished floor (tile, engineered wood, or laminate) goes directly on top. Total height addition: 15–25mm. This means you may need to trim doors, but you don't need to dig up the existing floor.
Overlay systems are popular because they involve far less disruption and can be installed room by room. Some manufacturers offer DIY-friendly kits.
Costs by Room
| Room | Typical Size | In-Screed Cost | Overlay Cost |
|---|---|---|---|
| Living room | 20m² | £800–£1,200 | £1,200–£1,600 |
| Kitchen | 15m² | £600–£900 | £900–£1,200 |
| Bathroom | 6m² | £240–£360 | £360–£480 |
| Hallway | 8m² | £320–£480 | £480–£640 |
| Whole ground floor (60m²) | 60m² | £2,400–£3,600 | £3,600–£4,800 |
Costs include materials and professional installation. DIY overlay kits are available from £30–£50/m² (materials only), but you'll need a plumber to connect the manifold to the heat pump system.
Best Rooms for Underfloor Heating
- Living room: Where you spend most waking hours. Even floor warmth is noticeably more comfortable than radiator heat. Hard floors (tile, wood) work best.
- Kitchen: Often has tile or stone flooring which conducts heat well. UFH removes the need for radiators that get in the way of kitchen units.
- Bathroom: Warm tiles underfoot. Small area means low cost. No radiator taking up wall space.
- Conservatory / extension: Often built on a concrete slab, making in-screed UFH straightforward during construction.
Rooms Where Radiators Are Fine
- Bedrooms: Carpeted floors reduce UFH effectiveness. You're usually asleep (under a duvet) so radiant floor warmth matters less.
- Hallways and landings: Often small areas where a compact radiator is more cost-effective than running UFH pipes.
- Upstairs rooms: Retrofit UFH on upper floors means working between joists, which is more complex and expensive. Upsized radiators are usually the practical choice.
Floor Coverings That Work Best
Underfloor heating works best with thermally conductive floor coverings:
- Tile and stone: Best conductors. Heat transfers quickly and evenly. Ideal for kitchens and bathrooms.
- Engineered wood and laminate: Good performance. Check the manufacturer's maximum temperature rating (usually fine for UFH).
- Vinyl / LVT: Good conductor, thin profile. Check for UFH compatibility rating.
- Carpet: The worst option — carpet insulates and blocks heat transfer. If you must use carpet over UFH, choose low tog (under 1.5 tog) with a thin underlay.
Response Time and Thermal Mass
Underfloor heating is slower to respond than radiators. An in-screed system may take 1–2 hours to warm a room from cold, while a radiator heats in 15–30 minutes. This isn't a problem in practice — you set the system to maintain a steady temperature using programmable thermostats, rather than switching it on and off.
The thermal mass of a screed floor is actually an advantage: it stores heat and releases it slowly, providing consistent warmth even after the heat pump cycles off. This works well with off-peak electricity tariffs — heat the screed overnight at cheap rates, and it radiates warmth throughout the day.
Related Guides
Frequently Asked Questions
Do you need underfloor heating for a heat pump?
No. Heat pumps work with radiators, underfloor heating, or a mix of both. However, underfloor heating is the most efficient emitter because it operates at low flow temperatures (25–35°C), which matches a heat pump's optimal range perfectly.
How much does underfloor heating cost to retrofit?
In-screed systems cost £40–£60 per m². Overlay (low-profile) systems cost £60–£80 per m². For a typical 20m² living room, expect £800–£1,600. Overlay systems are designed for retrofit and add only 15–25mm to the floor height.
Can you retrofit underfloor heating without digging up the floor?
Yes. Overlay systems sit on top of the existing floor and add only 15–25mm of height. They use thin pre-routed panels with pipe channels and are designed specifically for retrofit. Some homeowners install them as a DIY project.
Which rooms are best for underfloor heating?
Living rooms, kitchens, and bathrooms benefit most — these are rooms where you spend time standing or sitting, and where even, radiant warmth from the floor is most comfortable. Bedrooms and hallways can use radiators instead.
Can you mix underfloor heating and radiators?
Yes, and this is a very common approach. Underfloor heating in main living areas and radiators in bedrooms and hallways. Both work at the same low flow temperatures, and the heat pump serves them through a single system with zone controls.