Energy Saving Ordinance 2016 or KFW 55 for bungalow with air-water heat pump & controlled residential ventilation, optional photovoltaic

: I'll quickly address the LWWP with controlled residential ventilation and read the rest later. Thanks already for the feedback.

I understood that even the compact combin devices do not use the outside air but rather the air - after it has been used by the controlled residential ventilation for heat exchange - further.

So the indoor air is basically used twice and not the "winter air." Am I mistaken?

I completely agree with face26: It's generally hard to answer; it always depends on the individual case. If it's just about the money, you obviously have to calculate exactly what you gain from the interest advantages of KFW and the repayment grant. For example, with us, the surcharge for KFW55 is significantly lower than with you, so it does make financial sense (especially since you also get something from KFW431 for the energy consultant).

With your surcharge, you really have to look closely at the interest savings and also take your own environmental awareness into account. Forgoing KFW55 saves money that you can invest, for example, in a good geothermal heat pump and a photovoltaic system. I would argue that the average operating costs of the house over 10 years are about the same (better insulation with KFW55 vs. lower electricity/heating costs through photovoltaics and geothermal energy).

Here it is pretended as if KFW 55 were a different world than an energy saving regulation house. The differences are rather marginal. For us, an energy saving regulation house became a KFW 55 house with the air-water heat pump and a 6-chamber profile of the windows instead of 5. That was all, whether that is the difference between a well and a not well insulated house...

I would do the air-water heat pump again, KFW55 only if it pays off. Consumption is also very manageable with an air-water heat pump if the planning is not completely rubbish.

Here it is pretended as if KFW 55 were a different world compared to an Energy Saving Regulation house. The differences are rather marginal. In our case, an Energy Saving Regulation house became a KFW 55 house with the air-to-water heat pump and a 6-chamber profile for the windows instead of 5. That was all, whether that is now the difference between a well-insulated and a not well-insulated house...

I would do the air-to-water heat pump again, KFW55 only if it pays off. Consumption is also very manageable with an air-to-water heat pump, provided the planning isn’t completely messed up.

It always depends on the framework conditions: The cost factor for timber frame construction without a basement is marginal. Solid construction with brick without ETICS but with a basement is a completely different ball game to get from Energy Saving Regulation 2016 to KFW55. If you have actually planned without controlled residential ventilation, air-to-water heat pump, photovoltaics, T8 bricks (possibly filled), etc., the jump is somewhere above €40k.

You can’t generalize all that as always. The framework conditions are often too different for that.

: I will briefly address the air-water heat pump with controlled residential ventilation and read the rest later. Thanks in advance for the feedback.

I understand that even the compact Combin units do not use outside air but rather reuse the air — after it has been used for heat exchange by the controlled residential ventilation.

So the indoor air is basically used twice and not the 'winter air.' Am I mistaken?

that would then be an exhaust air heat pump. That is by far the worst thing on the market. It only works in passive houses.

The heat pump you mentioned, however, is a standard air-water heat pump that gets its supply and exhaust air through pipes from outside.

In general, it’s still debatable whether a combined unit of heat pump/controlled residential ventilation with heat recovery is sensible, or better separated.

I would separate controlled residential ventilation and heat pumps to keep the technology simpler and more interchangeable. If an air-to-water heat pump with an outdoor unit is an option, that would be my favorite - if the trench collector is not feasible. Otherwise, when buying new, you end up paying more or are tied to a manufacturer if you choose combined units. A controlled residential ventilation system can also be quickly bought and replaced yourself in an emergency, which is not the case with a combined unit. I don't think much of that, but it depends on what is offered to you if you have committed to the general contractor.

is correct regarding air-to-water heat pumps vs. exhaust air.

I would make insulation dependent on costs; you can't say that in general. There are bad energy-saving ordinance houses, there are good energy-saving ordinance houses, and KfW is also relatively easy to achieve, often even without special insulation purely through technology and thus only on paper. I would insulate where it is good and cheap to do so or where you will never get to it again.