Planning of heating and ventilation technology for KfW 40-Plus single-family house

Hello everyone,

we now have a planning meeting with the heating/ventilation technician in October/November.

In preparation for this, I have been wondering what I need to pay special attention to, what is important, etc., and I hope to receive some valuable planning tips for this very important trade.

Brief key facts about the planned new building:
- 2 full floors, clear raw construction height per floor 2.85m
- Kfw 40-Plus standard
- heated living area approx. 190 m²
- additional heating source: fireplace in the living/dining/cooking area approx. 60 m²
- floor plan: see post #254 in

The following information or prerequisites I have sent in advance (besides the planning documents) to the heating/ventilation technician:
Heating technology:
- split air-water heat pump or brine-water heat pump
- eligible for Bafa funding
- underfloor heating in all rooms (except garage with storage room) with a target temperature of 21-22 degrees in all rooms and 22-23 degrees in the bathrooms
- smart grid capable (for use of photovoltaic electricity)
- cooling function if possible
- hot water storage for a household of 4 persons

Controlled residential ventilation:
- cooling function or summer bypass

What do I need to pay special attention to? What tips do you have?

Shading concept is missing. In your views, there are venetian blinds drawn, but you do not mention them here. Nor do you mention which control options are planned for them.

Summer bypass in the controlled residential ventilation is nice-to-have but hardly brings any benefit. Just like the floor cooling via the heat pump. Especially with the summers of recent years and it’s getting hotter anyway. Tropical nights are also increasing, and without active air cooling, hardly anything can be achieved.

Enthalpy heat exchanger in controlled residential ventilation.

Regarding your fireplace: You are aware that it is never economical, unless you operate it with free wood and very intensively. Otherwise, the costs for purchase, maintenance, sweeping, fuel, etc. will always be higher than the electricity you will need for the heat pump without this device. It’s not a problem; some may appreciate it as a luxury item. It should only be clear that it is exactly that and brings no financial advantage.

that this is never economical

What is truly economical in house construction anyway

Shading concept is missing. In your views, there are indeed venetian blinds drawn in, but you do not mention them here now. Nor which control options are planned for them.

Summer bypass for the controlled residential ventilation is nice-to-have but brings almost nothing. Just like the underfloor cooling via the heat pump. Especially with the summers of recent years and it is getting warmer and warmer. Tropical nights are also increasing, so without active air cooling you can hardly achieve anything.

Sorry, didn’t know that this is relevant.

- On the ground floor (except for the north side = house entrance side), venetian blinds are installed all around. The remaining windows on the ground floor and upper floor receive electric aluminum shutters. Control of the venetian blinds and shutters is manual via Somfy TaHoma or automatic via sun sensors.
- The roof overhang is 60 cm with a 22° roof pitch.

I once read that both together (cooling function heating and controlled residential ventilation) can make about 2 to 3 degrees difference. I thought: "Better than nothing..." But in your opinion, costs and benefits are not in proportion?

Enthalpy heat exchanger for controlled residential ventilation.

Regarding your fireplace: You do realize that it is never economical, unless you operate it with free wood and very intensively. Otherwise, the costs for purchase, maintenance, chimney sweeping, fuel, etc. will always be higher than what you would need in electricity for the heat pump without this thing. It’s not bad, some may like it as a luxury item. It should just be clear that it is exactly that and brings no financial advantage.

Clear. For us, it’s also a luxury and decorative element. It is not installed for economic reasons. Thought the info might still be important.

What is really economical in house construction

Some (me) try to also include the economic aspect in house construction. We have a wood stove in our home, with which we heat 1/3 of the apartment in winter. At the same time, we cook on it and thus save electricity. The chimney was already there, only a stainless steel pipe was inserted for 1200 €. We otherwise heat with gas, but save about 1/3 of the heating costs through the wood stove. And I get the wood almost for free. Of course, heating with wood and cooking on the wood stove is also fun, even if it is a lot of work. But if it had not been economical in our case, we would have omitted it.

Thought the info might still be important.

In that case it is not relevant, since the heating must also run without operating the wood stove and must meet all criteria.