KFW 153 - Repayment grants and maximum loan amounts increase

Currently, to my knowledge, there is no obligation to install a Controlled Residential Ventilation system, neither from the current Energy Saving Ordinance nor as a requirement for any subsidies (BAFA, KfW, etc.). The KfW 55 and 40 efficiency standards can also theoretically be achieved without a Controlled Residential Ventilation system (with heat recovery) by using an efficient heating system (usually a heat pump) and (very) good insulation. However, a Controlled Residential Ventilation system, especially with heat recovery, reduces the heating load and makes it easier to meet these standards. Furthermore, it is recommended by many because practically speaking, in today's almost airtight building envelopes, there is no longer sufficient air exchange, which is very difficult to achieve through manual ventilation. This then has nothing to do with KfW etc., but with a healthy living environment and mold prevention.

For 40 plus, controlled residential ventilation with heat recovery is required. It is listed on the KfW site as part of the plus package. From this, one could also deduce conversely that 55 and 40 do not require controlled residential ventilation. But it makes it easier. And in my opinion, it makes sense anyway.

A controlled residential ventilation system, especially with heat recovery, reduces the heating load and makes it easier to achieve these standards.

Is there a rough guideline as to the order of magnitude of the heating load reduction we are talking about? I understand that it is individual, a rough framework is enough for me.

Nowadays, most newly built houses have underfloor heating installed. I hear from many that because of the underfloor heating, the houses are so dry that they regularly have to ensure moisture is brought into the rooms. From this I conclude that controlled residential ventilation only brings benefits from an energy perspective, and that only in the cold season. I just wonder if the high costs for installation and maintenance are worth it, if you will ventilate manually anyway.

Is there a rough guideline on the order of magnitude of the heating load reduction we are talking about? I understand that it is individual, a rough frame is enough for me.

Roughly 25%-30% in a typical single-family house

the floor heating
makes the houses so extremely dry

I wouldn’t know why the air with floor heating should be drier than with other types of heating. If anything, it’s rather the opposite.

Furthermore, the air does not become dry because of the heating; it is dry because it comes cold from outside. And cold air can hold less water than warm air, which is why relative humidity exists.

The controlled residential ventilation is also not intended to humidify the air. On the contrary, the constant supply of (dry) air from outside rather has the opposite effect.