The name alone feels warm. Yet so many households still flip it off at night, chasing quick savings and waking to a cold house and a bruised energy bill. The paradox: the more you stop it, the more it costs.
At 6:43 a.m., the kitchen tiles were colder than the mug in my hand. The thermostat had been off since midnight—“to save money,” the owner said—and now the floor felt like an unmade bed in winter. The heat pump hummed in the basement, pushing hard, sending hotter water through a thick concrete slab that had lost its calm. I watched the smart meter blink faster than my patience. You could feel the system sprinting to catch up, like a late bus accelerating into every red light. The silence of the night wasn’t free; it was borrowed. The house looked the same, yet the energy story had changed. One detail made all the difference.
Underfloor heating isn’t a radiator. It’s a slow giant.
Underfloor heating works like a warm ocean under your feet, not like a hot radiator on your wall. It heats a massive slab—screed, tiles, timber—that stores energy for hours and releases it gently. When you switch it off at night, you drain that reservoir. In the morning, you’re not just warming air; you’re recharging a heavy thermal battery. **Underfloor heating is not a radiator.** Treat it like one, and your bills rise while comfort falls. Keep it gliding, and the whole house breathes at the same pace.
In Parma, a family tried a simple experiment: off at 11 p.m., on at 6 a.m. At 7, the tiles were still at 18°C. By 9, the living room finally nudged toward 20°C, the heat pump forced to run at a hotter flow temperature, with a lower COP. The smart meter told the story—morning spikes, afternoon drift, evening hurry. When they stopped the nightly on/off and went with a small setback instead, consumption fell by 12% over two weeks, with fewer peaks and a steadier temperature. The kids noticed first. The floor “stopped being moody.”
Here’s the physics in plain clothes. Your slab is heavy—often 80–120 kg per square meter—and concrete holds a lot of heat. Drop the indoor setpoint 3°C for eight hours, and the slab cools deep, not just surface-level. To recover, your system runs hotter for longer, which hits efficiency hard, especially with heat pumps. Higher flow temperature equals worse COP. With boilers, deep cycles can trigger short-cycling and inefficiency. The result is a double loss: discomfort at dawn and a heavier bill by lunch. A small, steady flame beats a daily bonfire.
What to do instead: glide, don’t sprint
Use a gentle night setback—0.5 to 1.0°C, not 3–5°C. Keep flow temperatures low and constant, ideally with weather compensation, so the system anticipates the cold instead of chasing it. Set a base comfort level you actually live with, then trim, don’t slash. On windy nights, your slab stays in the goldilocks zone; on mild nights, it quietly sips. If your controls allow, run your circulation pump continuously at low speed and let the mixing valve or heat source modulate. The floor should whisper, not shout.
Common traps are painful and relatable. Killing the system at night “just to be safe.” Cranking morning boosts like an espresso shot for the house. Closing loops in unused rooms and forcing the pump to fight pressure. Setting thermostats to yo-yo. We’ve all had that moment when the bill arrives and you swear the house is gaslighting you. Let’s be honest: nobody fine-tunes weather-compensation curves every weekend. Start with one change—smaller setbacks—and watch what happens over two weeks. Comfort tells you whether you’re on the right track before your bill does.
This is what pros repeat on every job: underfloor systems love stability. They repay patience with quiet, even warmth and lower peaks.
“Run it low, run it long, and let the floor do the heavy lifting,” says Davide, a heating engineer in Emilia-Romagna. “Turning it off is like unplugging a fridge every night—then wondering why the milk is warm and the meter is angry.”
- Target night setback: 0.5–1.0°C (2°C max in very mild climates).
- Keep flow temps low: heat pump 28–35°C; condensing boiler 35–45°C where possible.
- Use weather compensation; avoid daily on/off schedules.
- Leave internal doors ajar to share heat and ease recovery.
- For long absences, drop to 15–17°C, not “OFF.”
The quiet math of comfort and cost
The floor is your slowest, steadiest teammate. If you invite it to sprint every morning, it will stumble—and charge you for it. If you let it jog at the same pace day and night, it turns into a background superpower, flattening peaks, smoothing drafts, hugging your budget. **Small setbacks save money; big ones cost it.** Insulation and climate change the margins, not the rule. In a well-insulated home, the slab barely cools; in a leaky one, deeper setbacks punish you twice. The win is strangely unflashy: a home that just feels right, with a meter that stops telling a melodrama at 7 a.m. **Comfort comes from consistency.** The trick is humble and a little boring—and that’s exactly why it works.
| Point clé | Détail | Intérêt pour le lecteur |
|---|---|---|
| Thermal mass loves stability | Keep the slab warm with low, steady flow temperatures | Lower bills and smoother comfort |
| Night setback, not shutdown | Reduce 0.5–1.0°C at night instead of turning off | Faster mornings, fewer energy spikes |
| Weather compensation | Match water temperature to outdoor conditions | Automatic efficiency, less thermostat fiddling |
FAQ :
- Should I ever turn underfloor heating off at night?Usually no. A small setback is cheaper and more comfortable because the slab keeps its stored heat and avoids costly morning recovery.
- What if I’m away for a few days?Drop to 15–17°C or use holiday mode. Turning completely off risks long, inefficient recovery and, in winter, condensation or frost issues in cold spaces.
- Does this advice change for heat pumps vs boilers?Heat pumps benefit most from steady, low flow temperatures. Boilers also gain from lower temps and fewer starts, though the savings are smaller than with heat pumps.
- What role does insulation play?Good insulation slows the slab’s cooling, making small setbacks very effective. In a poorly insulated home, big setbacks lose too much stored heat and cost more to recover.
- How long does a cooled floor take to warm up?Often 2–6 hours, depending on slab thickness, finish, and system output. That lag is exactly why nightly on/off patterns punish both comfort and cost.
