ᐅ Building a Monolithic KfW55 Home with a Basement – A Practical Approach!

Hello everyone,

I already feel a bit sorry for asking this question, as it has been indirectly discussed multiple times here in the forum. I am not concerned with whether KfW 55 is worthwhile or not; I have moved past that with the idea of a controlled mechanical ventilation system.

Originally, I did not want to build to the KfW 55 standard because of the basement. However, since we plan to build from the start with a controlled mechanical ventilation system, a heat pump is mandatory, and I am considering a photovoltaic system (without battery storage) due to owning an electric car, our architect mentioned that aiming for KfW 55 as a building standard would make sense (especially as the south-facing orientation is ideal).
We also plan to include a small fireplace (similar to a Plewa Classic).

Since we still have at least four months before consulting an energy advisor, I would like to ask the following question.

What do you think we would need in addition to meet the KfW 55 requirements effectively?
The draft plan currently shows a 36 cm (14 inch) masonry wall. Would we have to increase this to 42 cm (16.5 inch)? Or would triple-glazed windows suffice? Does the basement need to be heated? It is not intended as a living space, but it should be comfortable to spend time in.

Has anyone here already built a monolithic house with a basement to the KfW 55 standard? Surely, someone must have?

Yes, we are currently building a monolithic KfW 55 house with a basement.

36.5 cm (14.4 inches) Unipor Coriso blocks, air-to-water heat pump, triple-glazed windows. The basement was insulated with 12.5 cm (4.9 inches) perimeter insulation. The floor structure in the basement has the same insulation requirements as the ground floor and upper floors.

Photovoltaic panels are also planned for the roof. We are very close to reaching the 40 standard.

Why do you only contact the energy consultant in four months?

@Baufie: This is exactly the kind of information I was hoping for.

Where would you have needed to upgrade further to achieve KfW 40 standard?
Do you have a controlled residential ventilation system?
Is your basement heated? Do you have a utility basement or a living basement?

Regards,
Arthur

Baufie schrieb:
Why are you only approaching the energy consultant in 4 months?

We have just completed the initial design planning with the architect, and since the site development, surveying, and thus the building permit / planning permission will be submitted by us in about 4 months (planned), we still have some time.

Insulating the basement slab would have been necessary. Controlled mechanical ventilation, of course. The basement is heated—at least the hobby and utility rooms, as well as the entrance hall and the laundry room. The two other basement rooms are not heated.

I would involve the energy consultant promptly. Definitely before the construction drawings stage and also with regard to the costs.

Yes, I know that an energy consultant could probably tell me this better, but it’s still something I think about a lot. Would the following conditions be sufficient for KfW 55,(?)

- Air-to-water heat pump
- Controlled residential ventilation
- 12.5 cm (5 inches) perimeter insulation
- 36.5 cm (14 inches) Unipor Coriso
- Only double-glazed windows