KfW40 and KfW40+ with granny flat

  • Erstellt am 2016-12-15 23:46:31

timmaed

2016-12-15 23:46:31
  • #1
Hello,

We are still planning our house (in case anyone remembers: we had to increase our budget by €100k to realistically get something done...). Currently, we are considering integrating a small granny flat. We could use the granny flat well as a guest apartment for our parents because they live very far away. The parents would then happily stay with us for a week sometimes, and having a separate living area would be very convenient. I am aware that the funding is only paid proportionally according to the living areas. However, if the following calculation is completely wrong, then I don’t need to consider the granny flat any further.

Therefore, the following question:
Which (expensive) systems need to be duplicated for a two-family house with Kfw40 or 40+?
1. Does each residential unit have to have its own ventilation system? I have heard that this is required for fire protection reasons. What kind of controlled residential ventilation would that be? Is a decentralized little fan with a heat exchanger enough for the granny flat?
2. Does each residential unit have to have its own photovoltaic system with a separate battery?

If the systems do not need to be duplicated, then I arrive at the following calculation:

Best regards,
Tim
 

timmaed

2016-12-16 00:23:50
  • #2
According to the annex to the leaflet Energy Efficient Building (153):

Additional requirements for a KfW Efficiency House 40 Plus
A KfW Efficiency House 40 Plus meets the requirements of a KfW Efficiency House 40 and includes the following plus package:

    [*]An electricity-generating system based on renewable energies
    [*]A stationary battery storage system (electricity storage)
    [*]A ventilation system with heat recovery
    [*]A visualization of electricity generation and electricity consumption via a corresponding user interface
 

toxicmolotof

2016-12-16 13:27:43
  • #3
Okay, and what’s the point of the "Plus" if 40 is sufficient? The storage is not economically sensible, especially since it seems to be oversized for the size of the photovoltaic system.
 

ypg

2016-12-16 17:48:47
  • #4
As a layperson, I would say that a granny flat must be calculated autonomously in terms of consumption costs.
Besides, you probably need a parking space and a separate entrance as well as, of course, a building permit that allows a granny flat.
The basement (basement? must then be designed as living space (room height and size, windows, light, etc).
But if you don’t want to rent out this apartment anyway, then it’s not worth it.
Not to forget: Kfw55 or 40 generate incidental construction costs; the subsidies are there to cover part of it, but you always have additional costs.
It’s crazy what builders come up with to save a tenth here and there and desperately try to achieve these numbers.
 

Alex85

2016-12-16 18:09:51
  • #5


KfW 40+ provides an additional €5,000 repayment subsidy per residential unit. The hope here is probably to receive a total repayment subsidy of €10,000. If the technical package, except for the storage, is already planned, you could basically get the storage "for free." Another advantage is that when purchasing the photovoltaic system and the storage at the same time, you can deduct the input tax on the storage. If you install it afterwards, this is not possible.

I agree with you that the photovoltaic system most likely does not match the storage at the mentioned price.
 

timmaed

2016-12-27 14:23:29
  • #6
Hello and thank you very much for your answers!

I haven’t really become any wiser yet. I have also inquired with several companies, unfortunately without much success. I would probably have to invest money and go to an energy consultant. Therefore, I can only write down my current assumptions here in order to at least give all the kind tipsters the same level of information:

Regarding 1)
For fire protection reasons, the ventilation system must be decoupled. In fact, this results in two systems. A decentralized ventilation system in the granny flat seems possible, only the heat recovery rate must be appropriate.
2) A single photovoltaic system for the two residential units also seems possible. However, anyone who does not want to bill flat-rate will quickly face greater technical efforts here. I cannot say anything more about the prices of photovoltaic and storage; these were purely estimates. I rely on your experience, thanks for the hint.

The assumption is also correct that two additional parking spaces must be created due to the second residential unit. On 400sqm of land, that doesn’t make sense for me.

My current conclusion is: If no changes occur, then this idea is not sensible.
 

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