Which LVT technology is better for underfloor heating

Question

We are in process of building a house. Now we are in the state where we need to choose the flooring. We have two LVT options to choose from.

One is glue down LVT which is 2mm thick, the other one is rigid floating click LVT 5mm thick.

	glued	click
thermal conductivity [W/m.K]	0.17	0.07
thermal resistance [m².K/W]	0.01	0.07

The house has 3 rooms of size 15m² and one with size of 35m². There is a gas water heater powering the water underfloor heating. The walls are 40cm thick Ytong on top of which there is a 14cm of XPS. The windows are 3 glass layers pane plastic windows. Located in central europe.

Now the question is, which of those two flooring option will be more economic in the long run, with regards to heating the rooms.

The click vinyl should take longer to heat up, but it should keep the heat in longer (low conductivity, but higher resistance), the glued LVT is the opposite.

Given those parameters, which of those flooring options is a better choice?

The upfront cost, does not play a role in this question, I am interested in long term performance.

Answer 1

If you want to "keep the heat in" you need insulation below the floor you are heating. Not on top of it.

Insulation on top of the floor you are heating just means your heat has a hard time getting from your heating coils in the floor to the room, which generally means you have to run at a higher temperature to get the same amount of heat into the room, which increases heat loss to elsewhere (particularly if not insulated well below the heated floor).

Of those two, the one with lower thermal resistance, greater thermal conductivity is what you want for most effective and efficient operation of underfloor heat. But you also want something else (such as 10-14cm XPS) with a great deal of thermal resistance below the heated floor structure.