ᐅ Mechanical ventilation with heat recovery as a heating system?

Hello everyone,

We are currently planning a detached house of about 130m² (1,400 sq ft), with a basement, built with calcium silicate bricks and external thermal insulation composite system (ETICS) to KfW 70 standard, using a gas condensing boiler and solar collectors for domestic hot water.

According to our energy consultant, achieving this without a mechanical ventilation system with heat recovery is not feasible, and due to our construction method, controlled ventilation is advisable anyway.

My question is:
Would it make sense in this case to install a mechanical ventilation system with heat recovery and then use an additional electric heating element within the heat exchanger to provide heating through the ventilation system, thereby completely eliminating the conventional heating with the gas condensing boiler?

Thank you for your feedback.

Hello,

feud schrieb:
...we are currently planning a single-family house, about 130m² (1,400 sq ft), with a basement, built using calcium silicate bricks and an exterior thermal insulation composite system (ETICS) to meet KfW 70 standard, equipped with a gas condensing boiler and solar collectors for hot water production. According to the energy consultant, this cannot be achieved without a mechanical ventilation system with heat recovery, and due to our building method, controlled ventilation is advisable anyway.

Basically, that is not always true; it always depends on the specific conditions! Whether a mechanical ventilation system is necessary can be assessed. If it is desired for comfort reasons, that is totally fine.

feud schrieb:
...In this case, wouldn’t it make sense to install a mechanical ventilation system with heat recovery and then use an additional heating element in the heat exchanger to heat via the ventilation system and completely eliminate the conventional heating system with the gas condensing boiler?

This also depends on the individual case, meaning the specific heating demand and energy balance. Such a solution is only practical with relatively low space heating needs, since air is a poor medium for storing and transporting energy. Additionally, the heating element requires an energy source and could, in the worst case, simply be an electric direct heater! Furthermore, the efficiency of heat recovery is often significantly overestimated, which currently leads to substantial electricity costs in many new buildings because, for example, an installed exhaust air heat pump does not provide the required heating capacity.
Best regards.

Hello Euro,

thank you for your assessment!
The additional heating with electricity is also somewhat of a concern for me, but considering the costs saved on the conventional heating system, you can still "burn through" quite a bit of electricity.

Hello,

feud schrieb:
...The additional heating using electricity is also somewhat a concern for me, but the electricity consumed can often offset the costs saved on a conventional heating system.

That is correct! Therefore, it makes sense to calculate the actual energy consumption in advance. (Note that the values from the energy saving regulations are not suitable for this!) For very small scales, the heating system can be kept low in investment costs. In such cases, energy efficiency becomes less critical.

Best regards

Hello €uro,

I admit, the devil is tempting me this hour, but

€uro schrieb:
... The efficiency of heat recovery is also sometimes dramatically overestimated...

this statement of _yours_ puts my view of the common profession of engineers back into proper perspective

Kind regards

Hello,

Bauexperte schrieb:
...this, _your_ statement sets my view of the common profession of engineers back on the right track

Well, that’s a relief. However, this doesn’t mean that heat recovery is fundamentally pointless, as a “non-engineer” might immediately conclude. That’s precisely the subtle difference.

Best regards