ᐅ Underfloor Heating Beneath Wood Plank Flooring

chand1986 schrieb:
But then it works, why shouldn’t it?

For this simple reason:

For an underfloor heating system to function perfectly, the installed floor covering must effectively conduct heat. The extent to which this happens is expressed by the thermal resistance (R). This is calculated by dividing the material thickness (d) by the thermal conductivity (λ) for all layers of the floor covering. These two values influence each other, because the thicker the floor covering, the lower the thermal conductivity. To ensure the underfloor heating operates efficiently, the total thermal resistance must not exceed 0.15 m²K/W.

Theodorius schrieb:
I would like to have a floor made of natural, breathable wood that provides as much warmth as possible.

Even if that means higher energy consumption costs?

cschiko schrieb:
As I said, I didn’t install it myself, but both the timber supplier (who sells solid oak boards up to 20mm (0.8 inches) thick) and the installer (who did our staircase) see no problem with that.

They want to sell materials and labor as well.

Nordlys schrieb:
A master painter says clearly that floorboards and underfloor heating are a triple waste of energy. The eco-friendly guy lives on wood and just runs the gas burner, releasing CO2 into the air,

Anything is possible; everything can somehow be done. But it becomes completely pointless and contradictory—you don’t have to jump on the eco bandwagon here if you want to follow through on it at the expense of consumption and the environment.

@Mycraft

Except for this last figure here:

Mycraft schrieb:
0.15 m²K/W

I know all of that.

And admittedly, I have not calculated it for a solid wood plank assumed to be 20mm (0.8 inches) thick made of oak.

Now, underfloor heating also has reasons beyond efficiency. Appearance, free furniture placement options, and so on.

So my question is, how much efficiency is actually lost, and compared to what? If someone thinks X% loss compared to glued parquet is worth it, then fine.

According to most sources available online, most types of wood up to a thickness of 22m (72 feet) comply with a heat transfer coefficient of 0.15. It is clear that tiles have a better thermal conductivity. However, saying that underfloor heating and solid wood flooring cannot be combined is simply incorrect. Of course, this combination has its disadvantages. Ultimately, everyone must make their own decision, but it is important to choose the wood species and the thickness of the planks carefully.

chand1986 schrieb:
And admittedly, I didn’t calculate it for a solid wood plank assumed to be 20 mm (0.8 inches) thick made of oak.

25 mm (1 inch) Douglas fir: 0.025 / 0.13 = approx. 0.19 m²·K/W
27 mm (1.1 inches) Douglas fir: 0.028 / 0.13 = approx. 0.21 m²·K/W
20 mm (0.8 inches) oak: 0.020 / 0.13 = approx. 0.14 m²·K/W
27 mm (1.1 inches) oak: 0.030 / 0.17 = approx. 0.15 m²·K/W

For oak, 27 mm (1.1 inches) thickness is also possible... Douglas fir should in fact only be 20 mm (0.8 inches) thick.

Mycraft schrieb:
For the underfloor heating to operate energy-efficiently, the total value must not exceed 0.15 m²K/W (0.86 ft²·°F·h/Btu).

That is correct; the heat must transfer from the pipes into the floor, and the floor must then conduct it into the room. The 0.15 m²K/W (0.86 ft²·°F·h/Btu) limit, as @cschiko also mentioned, is met if the floorboards are not too thick (which I have also pointed out).

It is clear that the heat transfer to the room air is not as effective as it is with tiles, but the idea that heating costs would then skyrocket or that fuel demand would increase enormously is nonsense. Where would that even come from?

Initially, the lower thermal conductivity of wooden floorboards only reduces the heating capacity of the surface heating per square meter. It has no impact on the total amount of heat required to warm the house. So it is correct that with wooden floorboards, the underfloor heating needs to be designed differently than with tiles. This also applies to other floor coverings such as vinyl or parquet.

The only factor that can lead to an increase in fuel demand is a possible necessary increase in the supply temperature to compensate for the reduced heat transfer. By the way, with 15 mm (0.6 inch) parquet, this is not significantly different compared to 20 mm (0.8 inch) floorboards.

For gas heating systems, the energy efficiency is hardly affected whether the heating system runs at 30/25°C (86/77°F) or 40/35°C (104/95°F) (radiators typically modulate up to 55/45°C or 131/113°F); at most, this might mean about a 1% increase in gas consumption over the year.

For heat pumps, of course, the effect is more significant, but as already mentioned.