ᐅ Is KfW 100 standard sufficient?

... and then calculate the investment and financing costs of the technology against its electricity and maintenance expenses. After 15 years, the expensive equipment will need to be replaced. The loan conditions of the KfW loans are not that great compared to a standard mortgage loan with fixed installments.

Eco-friendly building makes sense but is currently caught between questionable KfW conditions and borderline promises from the heat pump salesmen.

We gave up on all this KfW nonsense, insulated well, installed a gas condensing boiler, and together with the 15% rule, we meet the Energy Saving Ordinance 2009. We also prepare for possible future upgrades such as solar thermal, photovoltaics, or heat pumps (if they ever become truly efficient).

KfW70 is not always the same as KfW70. That doesn’t automatically mean you save 30%. That’s simply unrealistic! It’s just number manipulation on a whole different level. Just because, on paper, using a heat pump brings you to KfW70, it doesn’t mean you will pay 30% less compared to an Energy Saving Ordinance standard (KfW100). The same goes for solar thermal systems. On paper, they look beneficial, but in real life, they often aren’t.

That said, in my opinion, saving 30% on approximately €40-50/month (about $40-50/month) will never be cost-effective. Especially since the metering fee (for me, €8/month (about $8/month)) doesn’t decrease by 30%.

A controlled residential ventilation system, for example, doesn’t save money financially, but it does have a benefit on paper. However, the comfort it provides makes it worthwhile to me!

That's more of a discrepancy between theory and practice. ;-)

In my opinion, if you are aiming for some level of comfort anyway (such as underfloor heating or ventilation mentioned by Bauexperte), the additional measures required for KfW 70 might be marginal. In my case, the building envelope (transmission heat loss) would even qualify for KfW 55, but since a heat pump is not desired, the house will simply receive a KfW 70 rating.

Bauexperte schrieb:
Good evening,


"The energy demand of a KfW 70 efficiency house is lower than that of a single-family house built strictly according to the Energy Saving Ordinance. A KfW 70 efficiency house only requires 70 percent of the energy compared to the reference building defined in the Energy Saving Ordinance, which is set at 100%."

Well, to be precise, it is 70% of the PRIMARY energy of the reference building. That does not mean you only need to consume 70% of the final energy supply ^^

Where is €uro, by the way? 😀

Bauexperte schrieb:
Good evening,


“The energy demand of a KfW 70 energy-efficient house is lower than that of a single-family house built strictly according to the Energy Saving Ordinance. A KfW 70 house requires only 70 percent of the energy of the reference building defined in the Energy Saving Ordinance, which is set at 100%. The lower the number (KfW 55, 40, or Passive House), the more energy is saved; and the higher the funding from KfW.” This is an excerpt from the explanation on the KfW website.

The step from the reference building to a KfW 70 is not very expensive; most providers nowadays already include underfloor heating as standard. What is usually missing then is a heat pump; at least a ventilation system with heat recovery should be installed if a gas condensing boiler is used. Additional cost for a ventilation system with heat recovery is about EUR 8,000–9,000.

Now you can calculate for yourself, based on rising energy prices, when a KfW 70 energy-efficient house will pay off 😉

Regards, Bauexperte

Underfloor heating is also what we want, and we have now decided on a ventilation system as well, although we still want to find out what additional cost this will involve.

perlenmann schrieb:
KfW 70 is not the same everywhere. That does not automatically mean you save 30%. That’s nonsense! It’s just number shifting to the power of ten. Just because I reach KfW 70 on paper — for example, with a heat pump — doesn’t mean I automatically pay 30% less compared to an Energy Saving Ordinance building (KfW 100). The same applies for solar thermal systems. On paper it looks good, but in real life it doesn’t.

Anyway, 30% savings on approximately €40–50/month will, in my opinion, never be worth it. Especially since the meter fee (for me €8/month) does not decrease by 30%.

A controlled residential ventilation system, for example, doesn’t bring financial savings, but on paper it does. However, the comfort it provides is worth it to me!

Yes, exactly, that’s what we were told during a conversation as well — that in the end, it’s just nicely calculated and you do not automatically save 30% on costs.

Thanks for all the responses.