Ventilation in new buildings (central vs. decentralized), noise disturbance

Hello everyone,

I am currently thinking about the ventilation in our planned new build (details: Kfw 70, 2 full floors + basement + cold attic, hip roof, 200m² living space). We live in the countryside and also like to keep the windows open. So we do not necessarily have to completely forego window ventilation.

I am torn between central controlled residential ventilation with heat recovery, central exhaust with decentralized supply air, and decentralized supply/exhaust air with heat recovery. The requirements I have are:
• Ventilation of the bathrooms (master bathroom, children's bathroom without windows, and guest WC without windows). With demand-controlled ventilation depending on usage
• I want to avoid having to ventilate through the windows every few hours while still maintaining high air quality
• Not too loud, I am very sensitive to noise when I want to sleep
• I am also sensitive to dry air, for example, I cannot tolerate air from air conditioning systems or in sports halls very well

The pros and cons of the individual systems, as I see them, I have listed below:

Central controlled residential ventilation
+ the most mature system
- expensive (I estimate about 10k€ to 13k€)
- more complex planning including suspending and boxing in the ducts
- (I heard from a provider of decentralized ventilation systems: as soon as I turn the ventilation up in the living room, more warm air is blown into the bedroom --> not desirable)
- The air quality of the prefabricated houses with controlled residential ventilation that we visited was always very poor. That makes me skeptical as well

Central exhaust with decentralized supply air
+ cheaper (maybe 2-3k€?)
+ should meet minimum requirements
- wasted energy (or can I use the heat energy somewhere else? I plan to use an air-water heat pump for heating and hot water generation. Maybe I can use the heat here in a sensible way). But I was advised against a complete exhaust air heat pump. Maybe there are combined exhaust/outdoor air heat pumps?
- cold due to decentralized supply air? (but I have also read that this is not a problem with reasonable planning because the supply air from outside mixes “sensibly” with the existing air)
- somehow contradicts the idea of energy-efficient houses. Nevertheless, this is probably more efficient than having the windows tilted open continuously.

Decentralized ventilation with heat recovery
+ If I just put one of these fans in the living-dining area and the master and children's bathrooms (+ ventilation of the WC), the minimum requirements should be met. I estimate about 3k€ for this (1k€ per device)
- If I want to cover all other rooms to completely avoid window ventilation, it will be more expensive (maybe ~8k€) and:
- I get a lot of holes in the building envelope
- I hesitate to install these things in bedrooms or children's rooms because I think they can be too loud.

Can you perhaps help me with the decision-making? Maybe by sharing your experience or confirming or refuting some of my arguments? I would also like to look at various fans in practice. Do you have any tips for that? I heard that you can do this somewhere in Berlin, but I come from the postal code area 5xxxx.

I look forward to your opinions.
Kiri

Take central with heat recovery... that's coming from me, who installed decentralized with heat recovery. Air quality is the same in both, electricity consumption and heat recovery in my opinion as well (or insignificantly worse with decentralized)... only it makes noise. My wife doesn't hear it, I hear it faintly. You get used to it, my children even like it.

Use central with heat recovery...

A heating engineer once told me: If you still want to ventilate manually, central systems are not recommended. Then the "dumb" fans (with intake through the window frames) are better because they are not bothered whether ventilation has been done or not. The central systems get confused because of that. What bothered me about the central systems was mainly the piping throughout the house, the maintenance effort, and ultimately the costs. For 200sqm, that might be three to five fans (= holes in the walls) that continuously and almost inaudibly keep the air fresh. Only with a lot of humidity (showering) do they ramp up. If I have the window open in the bathroom, that also eliminates that. Therefore my opinion: Use decentralized without heat recovery...

What is supposed to get mixed up there!?

Depending on the intelligence and networking of the systems, the ventilation control and the heating. If you ventilate, the setpoint in at least one room is no longer correct and the systems try to compensate, which always costs energy.

Depending on the intelligence and networking of the systems, the ventilation control and the heating. When you ventilate, at least one room no longer meets the target value and the systems try to compensate, which always costs energy.

Why should I ventilate if I have a ventilation system specifically for that?

P.S. One more question about the major maintenance effort. What do you mean by that?