Hello,
The contract itself says nothing about this. (Except that construction water and construction electricity are covered by the construction company.)
Then you bear the costs of construction drying yourself; as always: what is not in the contract is considered not purchased.
However, it also does not say that I have to provide a gas connection during the construction phase. It would also argue against this that the house "only belongs to me upon handover" (turnkey construction).
You ordered and paid for the gas connection and are also responsible for the ongoing installment payments; this initially has nothing to do with the contract for work concluded between you and your builder (BU). If the gas connection had not been available, dehumidifiers would have been used as needed. Their consumption costs would then have been borne by your BU (according to an excerpt from your contract).
You acquire ownership of your house step by step, not just upon handover. The path from signing to handover is governed by the contract for work. That is why it is so important to carefully review contracts beforehand so that no one-sided disadvantage leads to disputes.
It is quite "normal" that as soon as the underfloor heating is filled and the gas connection is in place, the drying program is started, and thereby the builder assumes the heating costs.
Best regards