Boiler room, new floor

[Awes78]

We have a boiler room where a heat pump, water pump with a tank will be installed.
We have broken up the concrete floor and decided to keep the clay pipes but replace the drain.
We're converting an old toilet connection to a drain for potential condensate water.

The walls are on their own base (is it called a "sula"?) and we will pour a new floor in about 75% of the boiler room. We will separate at the existing seam that was there before. The old boiler is on the remaining part.

What I'm wondering now is, the floor is uninsulated.
Can you lay out 50mm of Styrofoam as insulation and then pour on top of it?
Does that Styrofoam make any difference?
How about moisture, etc.?
We want to lay tiles on the concrete, without a moisture barrier.
The walls will be plastered and painted or tiled.

 

[Awes78]

According to the industry rules for wet rooms, there is an exception if:
If floors and walls with direct ground contact
lack underlying/external
insulation (capillary-breaking layer and/or thermal insulation) and are entirely
made of mineral material, the waterproofing layer can be excluded.

Do we change that condition if we lay 50mm of styrofoam on the ground and then concrete?