Bring heat from top to bottom

Following situation:
Our underfloor heating under the roof is new and at the moment we are heating the screed "through" (according to the screed layer's instructions).
For 5 days the heating is supposed to run at full power from today.
It will get nicely warm.
The access to the attic is unheated and I am wondering how I can distribute the room heat more sensibly.
Just leaving the door to the stairs open doesn't help much because warm air rises and once it is upstairs, it stays upstairs.

The plan is to set up a fan heater as a fan (of course without the heating function).

My question:
What do you think is better: blowing the warm air downwards or the cold air upwards?
I assume it makes no difference, but I would be interested to know what you think.

What is the benefit supposed to be? Expensive electricity for a fan to somehow use the heat from the necessary process of screed heating? Does it even make sense to blow this warm air, which in my understanding also contains a lot of moisture (@everyone .. or am I seeing this wrong?), somewhere else?

No, you really shouldn't do that, it would only be useful for mushroom cultivation. ;-)

Besides, the screed doesn’t want that either. Windows and doors must be closed. Only exchange all the air by shock ventilating three times a day.

The matter has become moot to my regret anyway, because the wonderful fan - as I just found out - does not ventilate without heating.

No, the air is not humid. The screed has been drying for many weeks and is supposed to be "thoroughly heated". (it may be that there are still some water residues in it, but nothing "identifiably moist")
The hallway is otherwise never heated and I thought it was a good opportunity to make it happy.
well ... that will work too ...