Exclusive ventilation heating in the prefabricated house

We built a house nearly two years ago (Bien-Zenker) with the Proxon ventilation heating system, an Efficiency House 55 with a fireplace and ground-source heat exchanger (the latter done by ourselves). I would do it again anytime. Of course, you need a drinking water heat pump, which is included in the package. It is very efficient in summer, somewhat less so in winter because it uses the exhaust air from the Proxon heating system (in summer: heating off, exhaust air >20 degrees, in winter heating on, exhaust air minus eight degrees...). For the four of us, we need about 900 kWh of electricity per year for heating water. I would always plan the ground heat exchanger, as it was able to warm the supply air to plus two degrees even at minus 15 degrees outside temperature (and cool it from 30 to 18 degrees in summer), which is why the Proxon can still operate efficiently even in the coldest winter. In both winters, the PTC auxiliary heaters were not used; instead, the soapstone fireplace was occasionally lit in winter. Auxiliary heaters are needed for comfort reasons in the bathrooms; we installed infrared panels instead of the offered convection fan heaters. This was not necessarily worthwhile, as IR heaters are a bit slower; we only use them when the children take baths. Regarding comfort: radiant heat is missing; anyone who wants to sleep at 23/24 degrees in winter and sit in a T-shirt in front of the TV won't be happy. The heating system delivers about 21 degrees, which is the limit with 42 degrees supply air (heat pump); you can, of course, achieve more with PTC auxiliary heating... but it is fun with a fireplace. What is great: always fresh air, absolutely no drafts, no noise, and the heating reacts quickly: when the sun shines through the south windows in winter, it immediately switches off, the same with fireplace operation.

...and regarding electricity consumption, 170sqm, 4 people: approx. 900 kwh for hot water (I have a measuring device for that) and an estimated 2000kwh for heating. We have everything in the house running on one meter, including household electricity (estimated just under 3500kwh), totaling 6000-6500kwh, of which the photovoltaic system (7.2kwp) contributes 2000-2500 kwh of self-consumption, so that including household electricity we consume about 4000kwh of electricity per year (and sell 5500-6000kwh photovoltaic output).
In addition, 1-2 cords of firewood...
The approx. 3000kwh for heating and hot water are certainly the lower limit for a 170sqm Efficiency House 55, as this is without any electrical auxiliary heating, which we do not use.

The Proxon is an option for me if:
- Efficiency House 55 or better, airtight!
- people less sensitive to cold (lack of radiant heat)
- south-facing house with many windows
- if photovoltaic and fireplace are planned anyway

I use 2000kwh with a Kfw70 house, with about 160sqm living space, 85sqm usable space (basement, not all rooms heated) for heating and hot water, 2 adults, 2 small children. Brine heat pump and deep drilling.

Oh yes, I forgot to mention above.... .

... in the USA, residential houses only have such a heating and air conditioning system ... if it is too hot outside, it switches to cooling and it is pleasantly cool inside the house ..

Yeah, and the humidity in winter is 0%... at least in the USA - but there the houses have holes as well.

Underfloor heating doesn’t work according to the principle "turn on the heating, room gets warm" (just as a side note) - normally it would be advisable not to let the house cool down at all, or so I’ve been told.
5500 kWh of pure electricity?! That’s 120 € / month - for a new building with the described limitations, that doesn’t sound very tempting. However, in Melvilli’s second post the consumption values are more favorable.

I would have thought the system only suits passive houses - for everything else it’s rather suboptimal.
Definitely very interesting Erfahrungsberichte - thanks for that.

Just throwing all the values out there doesn't bring much. Very important besides the number of residents, the heating load, etc., is also the climate zone. In the Rhine Graben, the air-to-air heat pump can work great in a KFW55 house, in Upper Franconia in the same house as well – but with significantly higher electricity costs and maybe only 19 DIN degrees in the living room.

With a bit of googling, you will find many homeowners dissatisfied with an air-to-air heat pump – and the consensus: air-to-air heat pump only at KFW55 (restricted according to climate region) and better.
Example Fiorino on page 1: KFW70 house and 5500 kWh consumption of electrical energy + wood for the fireplace for heating, ventilation, and hot water. The consumption is immense – unless the house is not about 350sqm and inhabited by 8 people or is located on the Zugspitze. But Fiorino is satisfied...
We have only with brine heat pump without fireplace in 200sqm (including partly heated basement) and 4 people including hot water in the coldest climate zone in the KFW70 house last year consumed less than a third of this value.