KFW 50EE or 40EE - Is the upgrade worthwhile?

Good morning,

we had a conversation yesterday with a construction company for the solid construction of a single-family house...

The construction company strongly advised against KFW40 as additional costs of €18,000 are to be expected and definitely no central ventilation with heat recovery and enthalpy exchanger... They install a decentralized ventilation without heat recovery and that is "super"...

Unfortunately, we are required to connect to the local heating network via biogas, hence the EE class.

I am not green enough to pay the surcharge just for peace of mind. Will the €18,000 additional costs for KFW40 pay off over 30 years or rather not?

Will the 18k additional costs for KFW40 pay off over 30 years or rather not?

Unfortunately, quite certainly not.
Of course, it depends on the costs you pay for the local heating network.

However, I would definitely prefer a central controlled residential ventilation system with enthalpy.
Why doesn't the BU want to? Too complicated?

Why this BU at all?

Unfortunately quite certainly not. It naturally depends on the costs you pay for the local heating.

There is no information about that. The development plan only included the option - but now the administration wants to make the connection mandatory when purchasing the property...

However, I would definitely prefer a central controlled residential ventilation with enthalpy.

Me too... My wife is now questioning it heavily since I have less knowledge than the construction company..........

Why does the builder not want to? Too complicated? Why this builder at all?

No idea... Zehnder was also an unknown company... Has a good reputation... I also woke up angry yesterday... masonry garage 6x6m with storage room is supposed to cost 65k... 3 prefabricated garages 34k... But I am not happy about the gap that then arises at the house

The BU recommends to you what it can do and wants to sell. It is by no means always the technically best solution in general.

I would also favor the central unit. An additional 18k for the upgrade to KfW40 sounds realistic and not exaggerated.

The surcharges for more insulation (filled or stronger stones/bricks) and everything that goes with it are significantly more expensive in solid construction than in timber frame construction.

My wife is of course now questioning it massively since I have less knowledge than the construction company..........

Then explain to your wife that construction companies like to use their knowledge advantage to align recommendations with their own interests (e.g., having more margin on option X than on option Y).

I also woke up angry yesterday... brick garage 6x6m with tool room is supposed to cost 65k... 3 prefabricated garages 34k... but I'm not enthusiastic about the space that then arises between it and the house

What space, speak in complete thoughts please!

Wiewowas welcher Zwischenraum, sprich´ bitte in ganzen Gedanken !

In the masonry garage, one side wall of the house is a garage wall; a prefabricated garage is attached to the house. According to the general contractor, wasps can occasionally inhabit this gap, or water can flow through it... I'm not happy about that...

Besides, I don't build a nice house just to put two ugly concrete blocks next to it... Of course, I don't get far at home with that opinion either...