Wood Coverings with Integrated Low-Voltage Power Supply for Heating of Nearly Zero Energy Buildings

Wood as a building material is a good thermal insulator, but in thin wood coverings this is not an obstacle to heating when the heating system is placed directly under the top layer. This study investigated the influence of a safety extra-low-voltage power supply (12 V and 24 V) on the surface temperature, response time and heat distribution of wood covering elements with an integrated heating system. Sixteen oak–plywood elements with copper heating wires 3 mm below the walking surface were tested in daily heating cycles; two of them were insulated with reflective foil or aerogel. At 12 V, the surface reached 29.1 ± 0.5 °C (about 5.6 K above ambient), within the comfort limit for floors, while at 24 V it reached 38.6 ± 1.3 °C (p < 0.001) and local checks appeared on the oak surface. The differences between elements were three times larger at 24 V (4.3 K compared with 1.5 K), but the relative non-uniformity was the same (CV of 8.5% at 12 V and 9.0% at 24 V; r = 0.98). Insulation under the element increased the temperature rise of the surface by 15–19%, while the type of insulation had little effect. A 12 V power supply is therefore a safe and sufficient solution for heating with wood coverings in nearly zero energy buildings.