Musketier
2012-12-07 16:33:40
- #1
Hello Gluecklich,
I had various options calculated.
But KFW house unfortunately is not KFW house.
You have different measures that work differently but can all lead to the KFW status. Each measure costs different amounts of money and brings different success in savings.
You can either insulate better or rely on alternative energies or design the heating differently.
Then there are of course intermediate solutions from several measures. Depending on the climate location, more or less of the individual measures is required.
To construct an extreme example:
Your house just fails to meet the KFW standard and thus counts as an Energy Saving Ordinance house.
Now you leave out the bay window, resulting in less exterior surface and less heat loss, pay a little less for the house and still suddenly have a Kfw 70 house. The energy saving will not be much, but the change pays off financially immediately.
An "exact KFW 70 house" will be very rare in practice. If you achieve the status, it will in practice be 99.99% better than the minimum requirements. Therefore the investment is usually too high but a 3/4 heating system simply does not exist.
So if you theoretically approach it, a KFW 70 house must be 30% better than an Energy Saving Ordinance house. The Energy Saving Ordinance house is based on an oil heating system.
If you now find somewhere what energy an Energy Saving Ordinance house consumes, take 30% of that and multiply it by the current OIL price, you might come up with the theoretical savings. That already looks different tomorrow because the oil price has changed. But this calculation has nothing to do with practice.
(@€uro I am aware that there are other energy sources involved and therefore my calculation will not be 100% accurate)
To now come to some concrete numbers:
Our house would be somewhere between Energy Saving Ordinance and KFW 70 with a gas condensing boiler and solar. With an air heat pump or surface collector we are better than the KFW 70 range (extra cost minus gas connection about 8K€). With deep drilling we almost reach KFW 55 but would have to insulate additionally.
Among the 3 heating alternatives, the surface collector will probably be the most economical for us, although all heating types are not that far apart. This of course also depends on the expected energy price increases. Ignoring the price increase, the gas condensing boiler would be the best alternative.
According to the calculation by our independent construction and energy consultant, the surface collector pays off after 17 years for us. Not included is the improved loan interest on the remaining 42K€ (50K€ KFW minus 8K€ additional cost for the heating). This reduces the payback period again.
The saving with the collector compared to the gas condensing boiler including interest must therefore be on average 8K€/17years/12 months = 40€ per month.
So you have a number from us, but it is of no use to you because you want to build a prefabricated house with a completely different cubature in a completely different part of Germany.
I had various options calculated.
But KFW house unfortunately is not KFW house.
You have different measures that work differently but can all lead to the KFW status. Each measure costs different amounts of money and brings different success in savings.
You can either insulate better or rely on alternative energies or design the heating differently.
Then there are of course intermediate solutions from several measures. Depending on the climate location, more or less of the individual measures is required.
To construct an extreme example:
Your house just fails to meet the KFW standard and thus counts as an Energy Saving Ordinance house.
Now you leave out the bay window, resulting in less exterior surface and less heat loss, pay a little less for the house and still suddenly have a Kfw 70 house. The energy saving will not be much, but the change pays off financially immediately.
An "exact KFW 70 house" will be very rare in practice. If you achieve the status, it will in practice be 99.99% better than the minimum requirements. Therefore the investment is usually too high but a 3/4 heating system simply does not exist.
So if you theoretically approach it, a KFW 70 house must be 30% better than an Energy Saving Ordinance house. The Energy Saving Ordinance house is based on an oil heating system.
If you now find somewhere what energy an Energy Saving Ordinance house consumes, take 30% of that and multiply it by the current OIL price, you might come up with the theoretical savings. That already looks different tomorrow because the oil price has changed. But this calculation has nothing to do with practice.
(@€uro I am aware that there are other energy sources involved and therefore my calculation will not be 100% accurate)
To now come to some concrete numbers:
Our house would be somewhere between Energy Saving Ordinance and KFW 70 with a gas condensing boiler and solar. With an air heat pump or surface collector we are better than the KFW 70 range (extra cost minus gas connection about 8K€). With deep drilling we almost reach KFW 55 but would have to insulate additionally.
Among the 3 heating alternatives, the surface collector will probably be the most economical for us, although all heating types are not that far apart. This of course also depends on the expected energy price increases. Ignoring the price increase, the gas condensing boiler would be the best alternative.
According to the calculation by our independent construction and energy consultant, the surface collector pays off after 17 years for us. Not included is the improved loan interest on the remaining 42K€ (50K€ KFW minus 8K€ additional cost for the heating). This reduces the payback period again.
The saving with the collector compared to the gas condensing boiler including interest must therefore be on average 8K€/17years/12 months = 40€ per month.
So you have a number from us, but it is of no use to you because you want to build a prefabricated house with a completely different cubature in a completely different part of Germany.