ᐅ KfW40 house offer with heat pump and mechanical ventilation with heat recovery— is it worth it?

The Geothermie-NRW links are not related to the slinky trench collector, so I would not rule it out yet.

Lumpi_LE schrieb:

What kind of house is that supposed to be?
I find that quite unrealistic.

This is a reasonable target value for building a KfW 40 house.
For example, a timber frame construction can achieve this quite easily.
Alternatively, a calcium silicate brick wall with 200mm (8 inches) of EPS insulation with a thermal conductivity of 0.032 W/(m·K) applied can also reach this range.

Monolithic construction methods, however, have difficulties meeting such requirements.

Please show me a KfW-40 house with a heating transmission coefficient (HT') of 0.14.

There is no doubt that it is possible, but a KfW-40 house from a prefabricated house manufacturer, as TE described, will never achieve this value.

It simply cannot be done with a timber frame construction, unless you eliminate the supply temperature at the windows. It also cannot be achieved with sand-lime brick and 200mm (8 inches) insulation.

Edit: Supply temperature for better understanding: We have about 20m² (215 sq ft) of windows and 160m² (1722 sq ft) of walls. The windows have a Uw value of 0.8. To compensate the windows with the walls and reach an HT' of 0.14, the walls would need a U value of about 0.06. That corresponds to roughly 60cm (24 inches) of insulation. And that does not even account for thermal bridges.

@Lumpi_LE Thanks for the overview. I only mentioned gas for comparison. Actually, I don’t want to have gas connected to the house, so in the end, I can also save the connection costs.

Lumpi_LE schrieb:

Please show me a KfW-40 house with a heat transfer coefficient (HT') of 0.14.
There is no doubt it’s possible, but a KfW-40 house from a prefab home provider as TE describes will never achieve this value.

It’s simply not possible with a timber frame, unless you omit the supply temperature to the windows. It’s just as impossible with calcium silicate blocks and 200mm (8 inches) of insulation.

Edit: To clarify supply temperature: We have about 20m² (215 sq ft) of windows and 160m² (1,722 sq ft) of walls. The windows have a Uw-value of 0.8. If I wanted to compensate for the windows with the walls to reach an HT' of 0.14, the walls would need a U-value of about 0.06. That means roughly 60cm (24 inches) of insulation. And that still doesn’t account for thermal bridges.

Everything is correct, but it’s off-topic here.
He received the U-values of individual components from his home provider. He is using them for the calculator because he has no other data. At this point, that is the only reasonable approach.

A completely nonsensical approach. If I want to know how many liters my car consumes per 100 km (62 miles) and someone tells me that the tank holds 60 liters (16 gallons), I obviously wouldn't assume 60 liters per 100 km.
But anyway, he already understood that and calculated with a heat transfer coefficient of 0.3.