ᐅ Ventilation in New Construction (Central vs. Decentralized), Noise Disturbance

Hello everyone,

I am currently considering the ventilation system for our planned new build (details: Kfw 70, 2 full floors + basement + unheated attic, hipped roof, 200m² (2,150 sq ft) living space). We live in a rural area and like to keep the windows open sometimes, so we don’t necessarily have to rely entirely on mechanical ventilation.

I am torn between a central controlled mechanical ventilation system with heat recovery, a central exhaust with decentralized supply air, and decentralized supply/exhaust with heat recovery. My requirements are:
• Ventilation of bathrooms (master bathroom, children’s bathroom without windows, and guest toilet without windows) with demand-controlled ventilation based on usage
• I want to avoid having to open windows every few hours while still maintaining high indoor air quality
• Not too noisy, as I am very sensitive to noise when trying to sleep
• I am also sensitive to dry air; for example, I cannot tolerate air from air conditioning or sports halls very well

Below are the pros and cons of each system as I see them:

Central Controlled Mechanical Ventilation with Heat Recovery
+the most mature system
-expensive (I estimate about 10,000 to 13,000 Euros)
-more complex planning, including suspending and boxing in ducts
-(I heard from a provider of decentralized ventilation systems: as soon as I turn up the ventilation in the living room, more warm air is blown into the bedroom – not desirable)
-the indoor air quality in the prefabricated houses with controlled ventilation that we visited was always poor. That makes me skeptical

Central Exhaust with Decentralized Supply Air
+cheaper (maybe 2,000 to 3,000 Euros?)
+should meet minimum requirements
-energy wasted (or can I reuse the heat energy somehow? I am planning to install an air-water heat pump for heating and hot water production. Maybe the heat can be used here in a useful way). I was advised against a complete exhaust heat pump. Perhaps combined exhaust/fresh air heat pumps exist?
-cold air from decentralized supply? (I have read that with proper planning this is no problem because the supply air mixes “appropriately” with the existing indoor air)
-somewhat contradicts the idea of energy-efficient houses. Still, it’s probably more efficient than constantly having windows tilted open.

Decentralized Ventilation with Heat Recovery
+If I simply install one of these ventilators in the living-dining area, the master bathroom, and the children’s bathroom (+ exhaust in the toilet), the minimum requirements should be met. I estimate about 3,000 Euros (1,000 Euros per unit)
-if I want to cover all other rooms to avoid window ventilation entirely, it gets more expensive (maybe ~8,000 Euros) and:
-I would have many holes in the building envelope
-I hesitate to install these devices in bedrooms or children’s rooms because I think they may be too noisy.

Could you please help me with the decision? Maybe by sharing your experience or confirming or disproving some of my points? I would also like to see different ventilators in practice. Do you have any tips? I heard it might be possible somewhere in Berlin, but I live in the postal code area 5xxxx.

I look forward to your opinions.
Kiri

Choose a central system with heat recovery...
that’s coming from someone who installed a decentralized system with heat recovery.
Air quality is the same in both cases, and in my opinion, energy consumption and heat recovery are also comparable (or slightly worse with decentralized)... only it produces noise. My wife doesn’t hear it, but I do, quietly. You get used to it, and my children even like it.

BeHaElJa schrieb:
Use a central system with heat recovery...

A heating engineer once told me that if you still want to ventilate manually, central systems are not recommended. In that case, the "dumb" fans (with air intake through the window frames) are better because they are not affected by whether you ventilate or not. The central systems tend to get confused by this.

What bothered me most about central systems was the ductwork throughout the whole house, the maintenance effort, and ultimately the costs. For a 200 sqm (2,150 sq ft) house, it's probably just three to five fans (meaning holes in the walls) that continuously and almost silently keep the air fresh. They only increase their speed when there is high humidity (like during showers). If I open the bathroom window, they switch off.

Therefore, my opinion is: go for decentralized systems without heat recovery...

What exactly is supposed to get mixed up there!?

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

Deliverer schrieb:
Depending on the intelligence and integration of the systems, the ventilation control and heating. When you ventilate, the target value in at least one room is no longer met, and the systems try to compensate, which always costs energy.

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

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