ᐅ Is a mechanical ventilation system with heat recovery advisable in this case or not?

Hello everyone,

We are planning to start building our single-family house next March.

It will be one and a half stories without a basement, with a 45° pitched roof, and 235m² (2,527 ft²) of living space featuring underfloor heating.
The annual primary energy demand is 50.62 kWh.

For heating, we have chosen a conventional gas condensing boiler combined with solar panels.

Regarding the decision to install a mechanical ventilation system with heat recovery or not, opinions are still divided.
(To clarify, we have not applied for KfW funding and therefore are not bound by KfW standards.)

The following constructions and U-values have been determined:

Roof:
U-value 0.19 W/m²K

Exterior wall:
U-value 0.18 W/m²K (20mm (0.8 inches) gypsum plaster, 175mm (7 inches) sand-lime brick, 160mm (6 inches) mineral wool insulation with lambda 0.035, 115mm (4.5 inches) solid facing brick)

Floor:
U-value 0.14 W/m²K

Windows:
Triple glazing

Our question is whether to integrate a mechanical ventilation system with heat recovery or not.

What are the general expert opinions or experiences regarding this?

Thank you in advance,

Marcel

Schulle84 schrieb:
...We are wondering whether to install a mechanical ventilation system with heat recovery or not.

Decide against solar thermal system, mechanical ventilation with heat recovery, possibly the 15% rule!

Best regards

Hello,

€uro schrieb:

Forgo solar thermal system, controlled mechanical ventilation with heat recovery, possibly 15% rule!

According to the latest findings, I would no longer dismiss solar; instead, I would install more. But - just my two cents :-)

Kind regards

Bauexperte schrieb:
....According to the latest knowledge, I would no longer condemn solar; instead, I would install more of it.

Well, opinions just differ. Solar thermal systems are the biggest deception in the energy saving regulations. That’s why general contractors / main contractors like to use this tool so much. ;-)
High profit with little effort, unfortunately to the disadvantage of inexperienced homeowners.
@ Bauexperte: Have you ever measured real yields in practical systems and compared them to the investment or financing costs, or compared them to the optimistic calculations in the certification?
Certainly not! Your opinion seems rather based on the colorful brochures of salespeople, without being able to professionally assess it yourself ;-)

Best regards

@Euro

We don’t have a general contractor, we assign the trades we don’t do ourselves.
My heating/plumbing technician says that because of the renewable energy share, we need to consider the minimum amount of solar with the gas boiler.

A heat pump is not an option for us, so it should be the gas boiler.

Best regards

Schulle84 schrieb:
...My heating/plumbing technician says that because of the renewable energy share, we need to consider a minimum amount of solar for gas boilers.

not entirely correct, § 7 or 9 of the Renewable Energy Heat Act (point 6 of the annex) also applies, meaning the so-called 15% rule.

Best regards