When to use equity?

I can't tell you yet, as we have not had any credit demand, as mentioned.

The bank contacted today .. due to the high equity, the loan can be called at any x arbitrary time. The equity can also be accessed only after the loan.

That is already an interesting statement. I will take it with me into the decisive meeting next Tuesday. For us, it could indeed be that from the time of the land purchase (expected in April) it will still take until May next year for the construction project to be realized (and the loan to be fully drawn). Even if I can use the equity at the end, I would avoid the mentioned "penalty interest." We will see whether that is possible at all with less equity.

For the sake of completeness, it should be mentioned that I threatened that I do not need the loan at all and would only take it out if it does not cost me negative interest and to have a bit more "breathing room."

The bank would therefore basically have the choice of either no loan at all or with the condition that it can be accessed before the equity as soon as negative interest threatens.

Nice for you. But this is rather not the situation of the average consumer to be able to set conditions to the bank.

Yes, okay. I won't be able to provide that either. As an aspiring retiree without much equity, I am anyway glad that I am still creditworthy for building a house.