Which type of construction suits us well?

Okay thanks for the tip, we will take a look at it.

Look for carpentry companies that, according to their homepage, only offer roof extensions. According to the homepage, there are also 2 carpentry companies here that do this. In fact, they build 1-2 houses a year with satisfied builders.

So you have 400,000 equity, the plot still needs to be purchased? Then about 600,000 euros remain for the house, or what is the plan?

That makes you very flexible in terms of construction method and you can easily reach 40 plus with the equipment.

Timber frame or solid construction have converged. There are no major technical differences.

The plot is purchased. 400,000 is planned as the maximum for the house construction. Okay thanks (:

OK with the ideas in the opening post and "only" 400,000, this definitely won't work. Slimming down is necessary.

It's not about building a house quickly but efficiently.
The energy standard should reach 40 plus

Since your emphasis is always on energy efficiency, I wonder if you are familiar with the Energy Saving Ordinance, including the new one with all the upgrades up to 40 and passive?
From 55 on, you only pay on the acquisition price of the technology without really being able to save on consumption anymore.
The Energy Saving Ordinance 2016 is now mandatory.
Everything else has to be considered additionally.