HEATLOSSPROUnderfloor heating output per m²
How much heat an underfloor heating loop gives depends on three things: the floor finish, the pipe spacing and the flow temperature. Here are typical figures, and a calculator to check a room.
In short: at 35 °C flow and 150 mm pipe spacing, underfloor heating gives about 85–100 W/m² under tiles or screed, 70 W/m² under engineered wood and 40–55 W/m² under laminate or carpet. Pipes at 100 mm give about 15% more, at 200 mm about 10% less, and each degree of flow temperature changes the output by about 3.5%.
Underfloor heating calculator
Output by floor finish and pipe spacing
Watts per m² of floor covered by pipes, at 35 °C flow.
| Floor finish | 100 mm | 150 mm | 200 mm | 300 mm |
|---|---|---|---|---|
| Screed or concrete, bare | 115 | 100 | 90 | 78 |
| Tiles or stone | 98 | 85 | 77 | 67 |
| Engineered wood | 81 | 70 | 63 | 55 |
| Laminate or solid wood | 63 | 55 | 50 | 43 |
| Carpet with thin underlay | 52 | 45 | 41 | 35 |
| Thick carpet | 48 | 42 | 38 | 33 |
Is it enough for the room?
Divide the room's heat loss by its floor area. If the floor can give more W/m² than the room loses, underfloor heating alone will do. If not, close the pipes up, choose a finish that passes heat better, raise the flow temperature a little, or add a radiator. Each room is different, so calculate its heat loss first: see how to calculate heat loss.
In the HeatLoss Pro designer you draw the underfloor heating zones on the floor plan, choose the finish and pipe spacing, and every room shows its heat loss against what its floor gives at the heat pump's flow temperature, with mixing valves, pipes and pump head checked too. Drawing is free; a full calculation with a PDF report costs €1.
Frequently asked questions
How much heat does underfloor heating give per m²?
At a 35 °C flow temperature and 150 mm pipe spacing, typically 85–100 W/m² under tiles or bare screed, about 70 W/m² under engineered wood, and 40–55 W/m² under laminate or carpet. Closer pipes and a warmer flow give more. The floor surface should stay below about 29 °C in living areas, which limits it to roughly 100 W/m².
Is underfloor heating enough to heat a room on its own?
Yes, when the room's heat loss per m² of floor is below what the floor can give. A well-insulated room losing 40–60 W/m² is easy; an old room with big windows losing 100 W/m² or more may need a radiator as well, closer pipes, or better insulation first.
What pipe spacing should I use for underfloor heating?
Commonly 150 mm in living rooms, 100 mm where more heat is needed (bathrooms, rooms with big windows, along outside walls) and 200 mm in well-insulated rooms with a low heat loss. Halving the spacing from 200 to 100 mm raises the output by about a quarter, not double.
What flow temperature does underfloor heating need?
Usually 30–40 °C, which is why it suits heat pumps so well. Every degree lower raises the heat pump's efficiency, so design the loops to deliver each room's heat loss at the lowest flow temperature you can.
Do the whole house in 5 minutes
Trace your floor plan and see every room's heat loss, the heat pump size and the radiator check as you draw. Free to try, nothing to install, no sign-up.
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