ᐅ Reliability of an energy calculation for KfW 55 – is it too high?
Created on: 20 Jun 2016 18:01
W
WT1987
Hello everyone,
For our new build with 2 full floors and a basement, we have now received a calculation for the entire KfW application. However, it seems to me that the numbers are being calculated quite high or may even be incorrect.
Some data about the house:
Is that the electricity consumption I should expect, or am I misunderstanding something? That seems very high!
Thank you in advance.
For our new build with 2 full floors and a basement, we have now received a calculation for the entire KfW application. However, it seems to me that the numbers are being calculated quite high or may even be incorrect.
Some data about the house:
- Architect’s plan shows living area: ground floor 75m² (807 ft²) & upper floor 70m² (753 ft²) (difference due to open space)
- Clear ceiling height: ground floor 2.7m (8 ft 10 in) & upper floor 2.5m (8 ft 2 in)
- Basement is unheated, air-water heat pump located in the basement
- Attic is not developed
- Air-water heat pump with ventilation system including heat recovery
- The expert assessor calculates a usable floor area of 277m² (2,982 ft²), which seems very high to me! He then uses this to estimate electricity consumption and arrives at a final energy demand of 4,860 kWh/year
Is that the electricity consumption I should expect, or am I misunderstanding something? That seems very high!
Thank you in advance.
Primary energy is subject to significant calculation factors:
https://de.wikipedia.org/wiki/Primärenergiebedarf
The building geometry also plays an important role – for example, our reference value was 57.15 kWh/m²a (5.31 kWh/ft² per year).
So, comparing these values in a general way only works to a limited extent.
https://de.wikipedia.org/wiki/Primärenergiebedarf
The building geometry also plays an important role – for example, our reference value was 57.15 kWh/m²a (5.31 kWh/ft² per year).
So, comparing these values in a general way only works to a limited extent.
WT1987 schrieb:
All data can be found in the attachment.Do you have the complete calculation available? What you posted is more or less just the result needed for the KfW. The full calculation can easily be 20-40 pages long, detailing everything like wall construction, roof structure, and so on.
BeHaElJa schrieb:
23.4 kWh/m²a (?), his value is 31.6 kWh/m²a, which isn’t that far off.. I find the difference per square meter quite significant. The discrepancies shouldn't actually be that large. A 25% higher energy demand essentially means you wouldn’t even qualify for KfW 70 anymore (if that still existed).
Most likely, a decimal point is misplaced somewhere. What’s really disappointing in cases like this is that the person preparing these documents should IMMEDIATELY notice such a 25% deviation from the standard KfW 55 calculation. You pay thousands of euros for this, and the guy doesn’t even perform a basic plausibility check. It’s frustrating that there’s no way to prevent this kind of sloppy work...
T
toxicmolotof21 Jun 2016 13:15And now I come along with 48 kWh/m²a (15,500 BTU/ft² per year) and still have KFW55.
So what now?
I’m always missing the reference building information here.
So what now?
I’m always missing the reference building information here.