Construction costs kfw70 vs. kfw55 vs. kfw40

The thicker wall construction would eat up too much living space for us

Well then switch from brick to wood and in the end you will even gain living space

Where can I actually find the requirements for a KFW40 house? I can't find anything about it on the KFW website. For KFW55 it is listed in great detail. Also KFW40+. But KFW40... I can't find anything about it. Does anyone know what needs to be done compared to KFW55?

KfW 40 usually means thicker bricks/stronger ETICS and stronger insulation in the roof for solid construction. Plus, of course, insulation under the floor slab, controlled residential ventilation with heat recovery, and experts from the requirements for KfW 55.

Construction expert on the go

Expert

KfW 40 usually means stronger brick/stronger ETICS and better insulation in the roof with massive construction. Plus, of course, insulation under the slab, controlled residential ventilation with heat recovery, and experts from the requirements for KfW 55.

For me, the difference from KFW55 to 40+ was as follows:

- Roof, windows, and slab remained the same.
- The air-water heat pump was replaced by the ground-source heat pump. Additional costs for the heat pump are covered by BAFA, and excavation work is free for us.
- The outer wall would have been KFW55, a 36.5 cm T8 or 42.5 cm T9 brick.
Now, for KFW40+, it would be 17.5 cm brick + 22 cm ETICS or 49 cm T7.
I chose the T7 because with over 200 m² of living space it didn’t matter.

If every square meter must be optimized, wooden construction is much better!

We chose bricks because it simply fit the budget better.
We only considered KfW 40+ because of the subsidies.
And I just don't want an ETICS.

Originally, we were also aiming for 180 sqm+, but when we actually saw some floor plans with less space—and liked them—we downsized to the essentials. There's simply more left for outdoor areas, vacations, etc.
But below 140 sqm, you just don't want to reduce the living space any further.