KFW funding sensible / Energy advisor, construction supervision?

Hello,
I had a conversation with a financial service provider yesterday and currently have an offer in hand for a 1.41% effective interest rate with 3% repayment.

The interest rates for KfW loans are lower, but I have to consider some conditions for new construction that make the new build more expensive.
If I have read correctly, I need to involve an independent expert who checks the construction execution of the KfW components.

I wonder whether the effort justifies the means. This is a bit unclear to me right now.

The KfW interest rate for program 153 is 1%. That is at least 4 percentage points. You can calculate for yourself what the interest savings bring you over the term and then compare.

Over what period are the 1.41%? Whether or not to take advantage of [KFW] should be carefully considered. Nowadays, I would no longer make use of it and would at most build according to [KFW] standards without applying for the funds.

It should be noted with the KFW, whether for example KfW 70 or 55, that construction supervision by an energy consultant is required. I was quoted costs of about €2500 for the construction supervision and the energy certificate. With the KfW 55, you get the loan currently at 0.75% interest and a grant of €2500. But it is ultimately tied to other factors such as energy-efficient building. It would really be interesting, as Koempy already wrote, for how many years the interest rate is fixed.

Similar to me. The energy consultant wanted €2,800. Although I am also building to the KFW 70 standard, I am leaving the subsidies aside.

The question is whether this really results in additional effort. The documents for the KfW application were prepared by our energy consultant together with the energy certificate. The confirmation will be created afterwards during the Blower-Door test. Apparently, this is only one more click in the program and an additional printout. For us, without extra charge. But many apparently want to make good money here.