ᐅ Installation of Heat Pump/Heating System – Before or After the Screed?

Yes, it depends on the composition/type. Each screed has its own specific temperature profiles.

i_b_n_a_n schrieb:

By the way, this involves cement screed without additives. I suspect that the timing and method of heating depend entirely on the type of screed and the additives used?

Yes.
There is a specific heating protocol for the screed.
An example for standard cement screed (although with today’s flow temperatures, 55°C (131°F) is often questioned – it seems to settle that 5°C (9°F) above the maximum flow temperature is sufficient):

With additives, for example:

There is so much talk about dry heating. I thought that functional heating is meant to test the operation of the underfloor heating system, not to dry the screed.

On the contrary, drying the screed too quickly (removing water) is actually not desired, because the water needs to bind through chemical processes and should not just evaporate. That is why there are these "careful" heating protocols. Otherwise, you could simply heat it up to check if the heating system works, and that would be it.

Tolentino schrieb:

There is so much talk about dry heating here. I thought that functional heating is intended to test the functionality of the underfloor heating system and not to dry the screed.

Of course, both purposes apply, and nowadays both are carried out simultaneously to save construction time and costs as much as possible.

According to our screed installer, the purpose of functional heating is to relieve stresses in the screed and thereby prevent (hairline) cracks. I was also surprised that we initially don’t need to heat at all (which would have been quite difficult without any heating). But what was done in the past without underfloor heating? They simply let it dry for a whole winter. So, if you have the time, this might actually be more cost-effective, especially since it is currently mostly done using electricity (heating rod), which can incur significant costs. Independently of each other, our energy consultant, plumber, and the drilling company all warned us against heating the screed with the heat pump, as it would extract too much energy from the borehole too quickly.