How a radiator actually heats
A radiator emits heat in two ways: convection (warm air rises) and radiation (infrared). The split varies by radiator type:
| Radiator type | Convection | Radiation |
|---|---|---|
| Panel radiator (modern) | 70% | 30% |
| Cast-iron radiator (heritage) | 50% | 50% |
| Tubular radiator | 65% | 35% |
| Designer radiator (towel rail) | 40% | 60% |
What a bad cover does
Closed covers (e.g. MDF boxes with small ventilation slots) block convection. Warm air can't rise, gets trapped, and the radiator "heats itself". Result:
- 15–30% measured heat loss
- Thermostat shuts off earlier, room stays cooler
- Heating bills go up 10–20%
What a good cover does NOT do
An open slat construction (like ours) has 30–40% free airflow area. Plenty for warm air to circulate freely upward.
The Fraunhofer Institute for Building Physics (IBP) tested several slat-style covers. For a wood-slat cover with 35% air-permeable surface:
- Heat output retained: 94–96%
- Loss: 4–6%
- Comparison: Curtains lose 30–50%, slotted MDF boxes 15–30%
Radiation heat is actually improved
Surprising side effect: wood reflects the radiator's infrared radiation back into the room warmer than cold plaster or white paint. The wood gets heated by the radiation and re-emits it slowly.
The result: the perceived warmth in a room can actually be slightly higher with a wooden cover — at nearly the same total heat output.
How to minimise heat loss
- Choose open slat construction (≥25% airflow area)
- Leave at least 3 cm gap between radiator and cover front
- Don't block top and bottom air intakes
- Wood instead of MDF — wood stores and re-radiates heat; MDF blocks it
- Wall mount with spacers if possible
Common myths debunked
Myth: "Radiator covers are generally bad for heating"
Truth: Bad covers are bad. Good ones (slat-style wood) have a negligible effect.
Myth: "Wood will burn from the radiator heat"
Truth: Radiators reach a maximum of 70–80°C. Wood ignites at 270°C+. Solid oak has excellent fire-behaviour rating (Class D-s2-d0).
Myth: "A cover significantly raises heating costs"
Truth: At 5% heat loss and average heating bill of €1,500/year, that's €75 extra. A good cover often recovers this through better heat distribution.
A cover with measurably retained heat output
Our open slat construction: 96% of original heat output retained.