Existing property - Discrepancies in the energy consumption certificate

Hello everyone,

we are currently interested in an existing property from 2010 and after the first viewing yesterday, we came across energy consumption discrepancies that are inexplicable to us as laypersons.

The energy certificate (consumption certificate) presented to us confirms an extremely high final energy consumption of 224 kWh/(m2a) by the current owner.

About the property:

[*]Year of construction: 2010
[*]138 sqm living space
[*]Kfw 70 certificate is available
[*]Blower Door Test: N50 = 0.80/h
[*]Heating and hot water via gas central heating (Fa. Brötje, 2010), old Brötje unit...
[*]Ventilation system available
[*]Underfloor heating throughout the entire house

According to the real estate agent, the property is heavily heated and due to currently 5 people in the household, there is supposedly a high hot water consumption – a statement which still does not seem entirely plausible to us given such a high consumption.

Are the statements of the real estate agent understandable to you? In other words, is such a high consumption realistic for a 5-person household, or do the numbers rather indicate defects in the heating, ventilation, or insulation?

We would definitely schedule another viewing appointment with a building inspector; are there any other steps/measures you would recommend to protect ourselves in this regard?

We are very grateful for any tips!

Does it mean 224 cubic meters of hot water? Why not. It depends on consumption

138m²*224kWh/m² = 30000kWh Gas. KfW 70 with [Kontrollierte-Wohnraumlüftung].

The hot water demand should not actually have such a large share. Either there are corresponding heating and ventilation habits or major defects.
Therefore: yes, the statement can certainly be true.

The heat has to go somewhere. Either directly through the chimney or the solar thermal system on the roof is heated.
Is the ventilation system without heat recovery? Perhaps significantly more ventilation is being done through the system than necessary?

It is not solely due to poor insulation. If there are technical problems, then they need to be addressed.

Is it possible to install insulation so incorrectly that it is completely ineffective?

Sure. Saturated mineral wool insulation or ventilated EPS boards due to skimping on adhesive = detachment. You would also notice this to that extent on the facade.

It is already a high consumption. If there is excessive bathing or constant heating to the outside (windows tilted open, etc.), you can manage it somehow.

Thank you very much for your assessments!