Controlled residential ventilation with heat recovery as heating?

Hello everyone,

we are currently planning a single-family house, approx. 130m², basemented with KS and ETICS in Kfw 70 standard with a gas condensing boiler and solar collectors for hot water generation. According to the energy consultant, this is on the one hand not achievable without [Kontrollierte-Wohnraumlüftung] and due to our construction method, the controlled ventilation is advisable anyway. My question now: Would it not be sensible in this case to install a [Kontrollierte-Wohnraumlüftung] with heat recovery and then also heat via the ventilation system by means of an additional heating element in the heat exchanger and thus completely eliminate the conventional heating using a gas condensing boiler?

Thanks for your answers

Hello,

...we are currently planning a single-family house, approx. 130m², with a basement, built with KS and ETICS to KfW 70 standard with a gas condensing boiler and solar collectors for hot water production. According to the energy consultant, this cannot be achieved without controlled residential ventilation and due to our construction method, controlled ventilation is advisable anyway.

Basically, that is not true; it always depends on the specific framework conditions! Whether controlled residential ventilation is necessary at all can be verified. If it is desired for comfort reasons, that is fine.

...Would it not be sensible in this case to install controlled residential ventilation with heat recovery and then also heat through the ventilation system by an additional heating rod in the heat exchanger, thereby completely eliminating the conventional heating using the gas condensing boiler?

That also depends on the individual case, i.e. the specific performance and energy balance. Such a solution only makes sense with relatively low room heating loads, since air is a poor "energy storage and carrier." In addition, the "heating rod" also requires an energy source and could, in the worst case, be an electric direct heater! Also, the efficiency of heat recovery is often dramatically overestimated, which currently leads to significant electricity costs in many new buildings because, for example, an installed exhaust heat pump does not deliver the required heating output.
Best regards.

Hello Euro,

thanks for your assessment! The additional heating with electricity is also somewhat a thorn in my side, but you can still "burn through" quite a bit of electricity for the costs you save on the conventional heating system.

Hello,

...The additional heating via electricity is also somewhat of a thorn in my side, but you can "burn" quite a bit of electricity for the costs you save on the conventional heating system.

That is correct! Therefore, it makes sense to calculate the actual energy consumption in advance. (Warning: Energy Saving Ordinance data are not suitable for this!) With absolutely low magnitudes, the investment effort for the heating system can be kept low. In such cases, energy efficiency plays a less important role.

Best regards

Hello €uro,

I gladly admit that this hour I am being ridden by the little devil, but

... Also, the efficiency of heat recovery is sometimes dramatically overestimated...

this, _Your_ statement puts my regard for the common profession of engineer back into proper perspective

Kind regards

Hello,

...this, _Your_ statement puts my view of the common profession of the engineer back on the right track

Well, that reassures me. However, that does not mean that heat recovery is fundamentally pointless, as a "non-engineer" would immediately conclude. That is the subtle difference.
Best regards.