ᐅ Is KfW 40+ achievable with a decentralized ventilation system?

Good morning,

I have a question that I couldn’t find a clear answer to on the internet. Maybe someone here knows for sure. For a KfW 40+ residential unit (it will be a multi-family building), is a central ventilation system mandatory, or is a decentralized ventilation system with heat recovery also acceptable?

I believe a decentralized system should be possible since KfW requires ventilation systems with at least 80% heat recovery efficiency, which some decentralized systems can achieve. However, I have also read in some places that a central system is mandatory.

Maybe you can provide more information on this. Thanks in advance.

Best regards,
Specki

You can also get up to x euros of the consulting costs reimbursed.

This doesn’t really help me at all...
Anyway, whatever was meant by it.

Decentralized systems are probably more practical for the apartment than centralized ones. Both options are feasible. Whether it can work entirely without would need to be calculated. As far as I know, it is not explicitly required, but I would expect that compensatory measures like additional insulation are more expensive and less effective.

Two quotes from the KfW website:

• A KfW Efficiency House 100, for example, meets the requirements of the Energy Saving Ordinance.
• A KfW Efficiency House 55 requires 55% of the energy of the reference building, and a KfW Efficiency House 40 only 40%.
• For the KfW Efficiency House 40 Plus standard, additional equipment and systems are required, such as for electricity generation and ventilation.

Here are the Plus components in detail:

• an electricity-generating system based on renewable energy on the property. Photovoltaic systems are most commonly used, or combined heat and power units; wind power is rare,

• a stationary battery as an electricity storage device,

• a ventilation system with heat recovery,

• a digital user interface that visualizes electricity generation and consumption.

However, I could not find any specification on the KfW site whether these systems are decentralized or centralized.
And on the internet, I find contradictory information.

Controlled residential ventilation is not an optional add-on, even if it might be stated that way by the KfW itself and you might practically not be able to avoid it. A central system is not mandatory. You need to meet specific requirements for KfW 40 (without +), and the path to achieve this is not strictly defined, even if the KfW examples suggest otherwise.
You will have to carry out a calculation.