Why is UFH ideal for heat pumps?

Underfloor heating operates at lower flow temperatures (30-45°C) compared to radiators (55-75°C). Heat pumps are most efficient at low flow temperatures, with COP improving by approximately 3% for every 1°C reduction. UFH at 35°C can achieve COP of 3.5-4.5, compared to 2.5-3.0 with radiators at 55°C.

What flow temperature should UFH run at with a heat pump?

Aim for 30-40°C flow temperature for maximum heat pump efficiency. At 35°C, well-insulated homes typically achieve 50-60 W/m² output which is sufficient. Poorly insulated homes may need 40-45°C flow temperature, which reduces COP but may be necessary.

How much does UFH cost per m²?

Screed (wet) UFH systems cost £40-£70/m² for materials, plus £20-£40/m² for screeding. Overlay (retrofit) systems cost £50-£80/m². Manifolds add £250-£500. A typical 80m² installation costs £4,000-£8,000 excluding the heat pump.

What pipe spacing is best for heat pumps?

Closer pipe spacing (150-200mm) is recommended for heat pump operation at low flow temperatures to maximise heat output. Standard spacing (200-250mm) may not deliver sufficient output at 35°C flow in less well-insulated rooms. 150mm spacing increases pipe use by 33% but improves output significantly.

Does floor finish affect UFH output?

Yes, significantly. Tiles and stone are best conductors giving 100% rated output. Engineered wood gives about 90%. Laminate gives 85-90%. Carpet with thick underlay can reduce output by 30% or more. With heat pumps at low flow temperatures, carpet may not deliver adequate heat.

TradeCalculator.co.uk

Underfloor Heating + Heat Pump Calculator

Design underfloor heating for heat pump operation at low flow temperatures. Calculate pipe lengths, circuit counts, heat output and compatibility with ASHP/GSHP systems.

Floor SystemScreed is most common for new build

Heat Pump TypeAffects COP at flow temperature

Floor Area

Total UFH area

Flow Temperature

35\u00B0C for best COP

Heat Loss per m²

From heat loss calculation

UFH Price per m²

Materials supply cost

How We Calculate This

This calculator designs UFH systems optimised for heat pump operation at low flow temperatures.

The formula

Heat output (W/m²) = Base output at flow temp × Floor finish factor

35°C flow: ~55 W/m² base (tiles)
40°C flow: ~70 W/m² base
45°C flow: ~85 W/m² base
Pipe length = Area ÷ Spacing × 1.1
Max circuit length: 100m

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.