Single-family house with KfW55/controlled residential ventilation or Energy Saving Ordinance standard - experiences and opinions?

We additionally had to pay €1750 for the energy consultant (50% of the total invoice), and perimeter insulation for around €2500.

That is really not much compared to the subsidy..

For us, that would be an extra €14,500 from the Energy Saving Ordinance to KFW 55 and the central controlled residential ventilation would be another €6000.

We will build according to the Energy Saving Ordinance including central controlled residential ventilation.

I would approach the matter the other way around.
Isn't it possibly more sensible to upgrade from KFW55 to KFW40+?

- "Not worth it," i.e. additional construction costs/KfW loan or repayment grant are disproportionate with KfW 55; "better to build without KfW in these interest rate times, it comes out about the same without KfW."

Kfw55... it’s not that expensive either,

Noise emission of the controlled residential ventilation," i.e. KfW 55 brings a ventilation system into the house that may cause disturbing noises (we are subjectively very noise-sensitive). And you don’t need the controlled residential ventilation, "with reasonable ventilation behavior it works without it too, is cheaper and anyway the better indoor climate."

With good house planning, you don’t hear the utility room. With proper controlled residential ventilation settings, you don’t hear the controlled residential ventilation.

"Energy saving ordinance is perfectly sufficient with energy and efficiency standard with reasonable wall construction and proper windows"; "the little extra energy saving is not worth the additional effort and bringing a noise source into the house." "Today’s houses based on the energy saving ordinance already have very low energy costs."

In my opinion, that is correct. Nevertheless, controlled residential ventilation should be considered separately and certainly does no harm to a house according to the energy saving ordinance, as it means comfort when ventilating.

You don’t need KfW 55, since you intend to live in the house yourself into old age. If you wanted to sell again, KfW 55 would be more important."

Who can see in a crystal ball what you will have to do in 10 years? I would see controlled residential ventilation independently: it is comfort. Manual ventilation is effortful and time-consuming. KfW 55: is okay, just like KfW 70. Not so decisive in terms of price now...

I would approach the matter the other way around. Might it be more sensible to upgrade from KFW55 to KFW40+

... whereas Kfw 40 is somewhat exaggerated if you don’t see the point or don’t have the money for the surcharge. Not necessary.

... while KfW 40 is a bit exaggerated if you don’t see the point or don’t have the money for the extra cost. It’s not necessary.

I see it differently. If I already have KFW55 and a controlled residential ventilation system in any case, there is really not much insulation missing to reach KFW40. That’s just a few centimeters. I would definitely put a photovoltaic system on the roof. Electricity is getting more expensive and eventually the electric car will be at the door. If I do KFW40+ now, I get the battery storage as a gift through the subsidy. Over the lifetime of the house/the insulation, you will save those few extra costs (minus the subsidy) in any case. If you ever have to sell, KFW40 is also more valuable than KFW55, because the trend is increasingly going in that direction in the future.

Thus, KFW40+ initially means a bit more investment, but it’s worth it. That’s how I see it at least, and that’s why my recommendation goes in this direction.

I see it differently. If I already have KFW55 and already have controlled residential ventilation, not much more insulation is really missing to reach KFW40. It's just a few centimeters. I would definitely put a photovoltaic system on the roof. Electricity is getting more expensive, and sooner or later the electric car will be at the door. If I do KFW40+ now, I get the battery storage as a gift through the subsidy. Over the lifetime of the house/insulation, you definitely save the few additional costs (minus the subsidy) again. If you ever sell, KFW40 is also of higher value than KFW55 because the trend in the future is clearly going more in that direction.

So KFW40+ initially means somewhat more investment, but it's worth it. At least that's how I see it, and that's why my recommendation goes in that direction.

Then you are exactly the one who sees the point and has the money.

Define your noise issue. Is it about the volume coming from the ventilation openings, or the volume of the ventilation unit (which should actually be shielded in the basement/attic/technical room)? The ventilation unit is always "loud"; it is the nature of the technology. The noises from the ventilation openings are extremely quiet. I only know it as you hear the airflow when the house is completely silent. Otherwise, not.

Hello Nordanney, basically both are our concern, as our bedroom is directly above the utility room. Here we would try to ensure proper decoupling of the controlled residential ventilation and also increase the reinforced concrete ceiling from 18/20cm to 22cm. Regarding the ventilation openings, we have also heard from acquaintances and noticed ourselves that audible noises can come from here. Perhaps something can be done here with other, preferably frictionless fans or silencers?