KfW70 with gas condensing boiler and solar is definitely not possible

I completely agree with you! I'm also not far from complete resignation. If I only considered the interest advantage from the KfW bank as a reward for the effort, the calculation still wouldn't add up for the necessary measures. But if a resale should ever come up, the energy certificate will play a role...

But as you already say, in the end the Energy Saving Ordinance traps you in an ugly corset, and sustainability, efficiency, and economy fall by the wayside.

However, if there should still be one or two undiscovered and sensible adjustments that reduce my primary energy demand by the last few required kWh, I'll gladly take them .

As klblb already said, maybe don't overestimate Kfw70, especially not for the sole purpose of an energy certificate, which doesn't even indicate how much energy you actually end up consuming.

We bought a 2-year-old house (semi-detached) (without energy certificate, 35.5 aerated concrete, gas condensing boiler, solar thermal, no controlled residential ventilation) with the seller's statement that it is not a KfW70 house, but the consumption is close to KfW70. I could have had that confirmed by invoices.

In retrospect, I have to say, yes, that's how it is. But I can actually do without an energy certificate. And even with a later sale, you might even be able to prove that your consumption is below KfW70 regardless of the energy certificate.

Hello Phil,

I am not an expert in these matters – especially since there are several ways to Rome – but I can answer you from my professional experience.

Our KfW 70 efficiency houses are equipped with the following standard values for the building envelope:

Floor slab: 0.26 W/(m2K) => reference building 0.35 W/(m2K)
Windows (glass and frame): 0.9 W/(m2K) => reference building 1.3 W/(m2K)
Wall (36.5 monolithic): 0.23 W/(m2K) => reference building 0.28 W/(m2K)
Roof: 0.17 W/(m2K) => reference building 0.20 W/(m2K)

Considering the thermal bridges => 0.05 W/(m2K) => we usually achieve a calculated primary energy demand of Q 58.3 kWh(m2a) [reference building Q 83.41 kWh(m2a)] when using an air-water heat pump and if the building is not located on the Zugspitze; see attachment.

However, we already cover other values from the BB by default; the 200 mm insulation in your list is only one of several points in which we probably differ.

If a builder wishes to install a gas condensing boiler with solar heating support, they can generally assume that this is not sufficient to achieve the KfW 70 status; usually, the installation of a ventilation system with heat recovery is required. This is sufficient in most cases to qualify for the KfW promotional loan; in very rare cases (depending on the location), additional insulation must be added. In the next step (KfW 55, attachment), only a ventilation system with heat recovery as well as a filled block with the value 0.20 W/(m2K) are missing.

I wrote at the beginning that there are several ways to Rome; this is to be taken literally because there are several calculation methods to provide the KfW proof. And then there are differences in the persons who provide the proof. We have structural engineers who calculate concrete in water and others who orient themselves on the actual conditions. Since ultimately everything depends on the paperwork, it is quite possible that your planner belongs to the first category or takes the “apparently” worse calculation method.

Subject KfW 70 efficiency house – As long as the subsidies are secondary for you (they are not really much cheaper at the moment anyway), I would not worry too much. A single-family house built according to the Energy Saving Ordinance is not really bad; from my personal point of view, it is often the better choice, considering the not exactly small monetary effort. What is important in my opinion is not that the paper says “You have built a single-family house subsidized according to KfW 70,” but the actual energy consumption. In case of sale, this will interest a potential buyer more than anything else.

Rhenish regards

I contacted a KfW-licensed energy consultant today and also explained the circumstances and framework conditions to him again. He was also very surprised that the primary energy demand for KfW70, despite controlled residential ventilation/heat recovery and solar thermal energy, should not have been met and suspected calculation errors (of whatever kind) when comparing some data.

So I have 2 options now.

1) I have the energy saving ordinance certificate (and certificate for KfW efficiency house) checked again carefully and corrected if necessary. The probability that I would then have a subsidizable house would probably be quite high. This would only be about having an energy certificate in the end that, for example, issues an A instead of efficiency class B. Cost, estimated €500.

2) To also be able to apply for the KfW loan, the KfW appraiser must of course be commissioned for the entire planning and construction supervision in order to be able to issue the required certificate at the end. Even if he would reduce the work and review effort required by the Federal Audit Office in my favor here, the cost, which is based on the state fee regulations, would amount to several thousand euros. *Cough...*

So I will probably really leave all the KfW stuff alone, take advice again to make sure that my concept is not quite planned off the mark in terms of demand, and if necessary, only correct the energy certificate later - should a resale ever be discussed.

The question is what I do with my previous planner if he really took the calculation too lightly and thus at least partly based it on incorrect values, which makes the current energy balance of the house worse than it actually is...

Hello,

2) In order to also be able to use the KfW loan, the KfW appraiser must of course be commissioned for the complete planning and construction supervision in order to be able to issue the required certificate at the end. Even if he were to break down the work and inspection effort prescribed by the Federal Audit Office in my favor here, the cost, which is based on the state fee schedules, would have to be calculated at several thousand euros. *Cough.....*

With all due respect – that is nonsense ....

The energy consultant – what even is a licensed energy consultant? – has to fill out form 153 for you "at the beginning" (the structural engineer also has to do calculations for this) and at the end provide proof that a KfW 70 efficiency house was actually built. This certainly does not cost several thousand euros!

The only question is, what do I do with my previous planner if he really took it too easy with the calculation and thus at least partially based it on incorrect values, resulting in the current energy balance of the house being worse than it actually is...

Inform the result of the discussion with the above-mentioned energy consultant and then see what happens

Rhenish greetings

Hello construction expert,

"licensed" may be incorrect. However, the expert must be approved by the KfW and thus authorized to issue the corresponding certificates. This, for example, does not apply to my civil engineer. Had I known that beforehand, I would certainly have approached the matter differently.

The fact that the certification process is supposed to involve such costs shocks me on the one hand, but on the other hand, I was referred to the information sheets on [Programm 153 (energieeffizientes Bauen)] from the KfW, where the requirements for the expert are described. This, combined with the fact that almost every appraiser is paid very expensively, somehow makes it comprehensible.

But I will definitely inquire further about the costs. After all, they are also calculated based on effort—and the contacted "Energie-Effizienz-Experte" lives only 1 km away from me.