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.
T
toxicmolotof20 Jun 2016 18:52Think about it... Which part of the house does the heating system actually warm, and where does the heat encounter resistance?
This applies regardless of whether it’s living space or non-living space.
By the way, I find it hard to imagine that there is no heating system in the basement.
This applies regardless of whether it’s living space or non-living space.
By the way, I find it hard to imagine that there is no heating system in the basement.
BeHaElJa schrieb:
What is 4860 kW/a supposed to mean?! kW is a unit of power... an offshore wind turbine has 5000 kW.
The calculation still seems odd to me... do you have a mechanical ventilation system with heat recovery?Yes, we do have a mechanical ventilation system with heat recovery. The exact performance specifications are listed in the previous attachment.
I just want to get an idea of the approximate annual electricity consumption with this setup.
Regarding the calculation of usable floor area, I have now received an answer: for the KfW calculation, the entire building is considered, including basement or attic, whether heated or not—it doesn’t matter! They also use a ceiling height of 3 m (10 feet) in the calculation because of this factor.
According to the calculation, you will consume 4866 kWh of electricity – about 90 € per month, including domestic hot water.
For 250 sqm (2,690 sq ft), this is not unreasonable with an air-to-water heat pump – although the annual performance factor would be very low...
For example, we have 7663 kWh of primary energy for 190 sqm (2,045 sq ft), but with a ground-to-water heat pump, the final energy consumption is correspondingly lower.
What you will actually consume is a completely different matter.
For 250 sqm (2,690 sq ft), this is not unreasonable with an air-to-water heat pump – although the annual performance factor would be very low...
For example, we have 7663 kWh of primary energy for 190 sqm (2,045 sq ft), but with a ground-to-water heat pump, the final energy consumption is correspondingly lower.
What you will actually consume is a completely different matter.
WT1987 schrieb:
Hello everyone,
regarding
- The building inspector calculates a usable floor area of 277sqm (2980 sq ft), which seems very high to me! He then uses this figure to estimate electricity consumption and arrives at a final energy demand of 4860 kWh/year.
Then take a look at the usable floor area calculation. Sometimes garages or similar areas are included, which can add a few square meters more than expected.Similar topics