ᐅ Two-layer instead of three-layer parquet for underfloor heating and glue-down installation?

Hello everyone,

We want to install engineered hardwood flooring (oak plank, wide board) with underfloor heating and cooling in our new build. The most common option is 3-layer click-engineered wood, which is suitable for both floating and glued installations. Because of the underfloor heating, we definitely want to go with glued installation.

Does it make sense to choose the thinnest possible wood flooring due to wood’s relatively high thermal resistance? I understand that the heating will run almost constantly, but won’t a 15 mm (0.6 inch) thick plank still respond too slowly? Will the surface temperature of the wood flooring even reach the same temperature as the screed (29°C (84°F))?

There is also 2-layer engineered wood (10 mm (0.4 inch)) with a wear layer of 3.5 to 4 mm (0.14 to 0.16 inch). If glued, does this have any disadvantage compared to a 3-layer construction (15 mm (0.6 inch)) with the same wear layer? As I understand it, a 3-layer construction is only really necessary for floating installation, right?

Thanks for your input! Best regards

You won't notice a difference of a few millimeters. The minimal difference can be calculated, but you can't feel it underfoot. 29 degrees Celsius (84°F) will never be reached with any hardwood flooring. A supply temperature of 29 degrees Celsius (84°F) will result in about 26 degrees Celsius (79°F) on the surface of the wood.
I currently have 13.5mm (0.53 inches) plus adhesive.

Addendum: No, you do not have any disadvantage if you install the flooring in two layers.

nordanney schrieb:

You won’t notice a few millimeters. The minimal difference can be calculated, but you won’t feel it underfoot.

A 2-layer with 10 mm (0.4 inches) should have about 0.076 m²·K/W (square meters kelvin per watt).
A 3-layer with 13.5 mm (0.5 inches) about 0.11 m²·K/W.

These values must be considered when sizing the heating system, right?

nordanney schrieb:

Addendum: no, you don’t have any disadvantage if you install it as two-layer

Ok, thanks. I suspected as much. I was still concerned that the parquet might be more sensitive to pressure because of the thinner subfloor. Two-layer is definitely somewhat cheaper.

Anteilseigner schrieb:

The values need to be considered when sizing the heating system, right?

No. At most, you differentiate between wood and tiles. If the screed is 3mm (0.1 inches) thicker, you don’t recalculate. Or if a heating circuit is 2m (6.6 feet) longer.

Anteilseigner schrieb:

I was still concerned that the parquet might be more sensitive to pressure due to the thinner underlayment....
Two-layer is definitely somewhat cheaper.

You don’t need to worry about that. The wood type used as the surface is more relevant. Maple or wenge do make a difference.