ᐅ Ventilation Concept for a Single-Family Home: Natural Ventilation, Air Leakage Devices (ALDs), Door Gaps – What Are Your Thoughts?

Of course, thorough planning is essential. I have already mentioned the material cost for the central ventilation system.
In addition to planning where and how much air should be supplied, the openings through the ceiling for the vents should ideally be planned as well, so installation can proceed relatively quickly.
Instead of the flexible duct option, you can also use the spiral duct variant. For this, a riser shaft and a dropped ceiling of about 20cm (8 inches) in the hallway are needed. Depending on the floor plan, additional partial dropped ceilings may be required. You can find ready-made plans starting at €10,000 including materials for self-installation.
Good brands include Maico and Pichler, among others.

GeraldG schrieb:

Even in the current old building, we ventilate several times a day to keep CO2 levels below 1200 ppm.

This morning I got up late again, and a glance at the measuring device showed a value of 425, which clearly reflects the air quality, roughly comparable to outdoor air. Of course, I lived well enough without this all my previous life, but now, living in a new KfW40 house, I would never want to go without it given my user behavior.

You are building what will hopefully be a nice home for yourselves and are allowing a few extra square meters beyond what might be strictly necessary. Good!
But — and this is almost my mantra — why does this mindset of comfort suddenly stop at such important points?
If construction costs are €3,000–4,000 per square meter, wouldn’t it be worth sacrificing just a few square meters to first and foremost install a central mechanical ventilation system with heat recovery? Why not include air conditioning, which is also affordable and ensures maximum living comfort?
People invest in the most expensive fireplaces, large garages, elaborate fences and mailbox setups, KNX (home automation), and more, yet they skimp on indoor air quality and overall comfort. That’s something I would never do for myself; inside, I would always want the comfort I value. I see this so often around me and can never understand it: expensive, semi-professional “smart home toys” but no roof over the terrace and yearly complaints about its absence.
You won’t solve this topic with pure calculations alone, and of course there are always pros and cons. In a modern house with children, where ventilation discipline can’t be expected and many rooms are mostly closed off, calculating performance values is pointless. We live as a couple in completely open spaces, so we could theoretically live well even without mechanical ventilation—but we would choose it again.

Sonar87 schrieb:

Which specific brands or models of central ventilation systems can you recommend?

In 2021, we had the Zehnder QTR350 installed. There are many older threads about it here. As a layperson, I’d say Zehnder can be seen as a market leader. The unit is by no means noisy, and there are people here who installed it themselves as beginners (I did not). Zehnder itself offered custom planning; unfortunately, my general contractor did not implement this well, so I would get involved directly to make sure it fits your needs. I personally later bought a module to control it via an app. The technology seems quite straightforward, so fundamentally there probably aren’t many differences between brands.
We paid just under €11,000 through our contractor in 2021.

Sonar87 schrieb:

We are also considering installing an external air conditioning system because of the large panoramic windows and potential overheating in summer. Do you have experience with combining ventilation and air conditioning, and can you recommend effective systems or approaches?

I fully agree on that as well. We only decided on it quite late, which still surprises me given the increasingly warm summers and our rising expectations for comfort.
We also have large glass fronts and, luckily, external venetian blinds (Raffstore) in front of them, which effectively keep out heat when you tilt the slats horizontally, while still letting in plenty of light (unlike roller shutters). In summer, we sometimes leave the slats set like that all the time. But once the heat gets inside, it naturally takes a long time to get rid of it again, especially because modern houses are so airtight today.
Our air conditioning, combined with the photovoltaic system on the roof, runs quietly in the background and keeps the rooms pleasantly cool. It can also be controlled remotely (and can provide some heating in winter).
I looked at various models at specialized dealers and ended up choosing Daikin, even though they cost a bit more. We picked a stylish silver unit for the open living area.
My advice: go for it. Don’t hesitate to give up a few square meters or something else, because these two components really enhance your indoor living quality. In summer, you will have plenty of electricity “in surplus” from the solar panels anyway.

Thank you all for your feedback so far – it has truly been very helpful.

For us, the cost is less of an issue. The roughly 16,000 EUR would generally be manageable. It’s more that, as non-experts, we sometimes simply don’t know who to trust on this topic. Our architect believes it’s better without a central ventilation system. Today, I spoke with the ventilation expert who designed our ventilation concept, and he said that only about 15% of homeowners actually install such a system. The construction company itself is rather neutral, while an in-house architect tends to recommend a ventilation system.

In addition, I’m often away for work, spending 15–18 days a month in hotels – often in Asia – where I regularly struggle with constantly running, non-switchable, and often very loud ventilation systems. I’m extremely sensitive to noise and need complete quiet to sleep. My brother, who is also an architect, built with his construction company and installed a central ventilation system that is so noisy that neither the manufacturer nor an expert has been able to find a solution so far. All of this makes the decision more difficult for me.

In the end, it feels a bit like buying a car: One person swears by BMW, another explains with good arguments why a Kia is perfectly fine. But the more you research yourself, the more questions come up.

That’s why it’s really good to hear the different perspectives and experiences here, to better assess the topic. So thank you very much for every comment – it really helps us a lot in making our decision.

Sonar87 schrieb:

In addition, I spend 15 to 18 days per month working in hotels – often in Asia – and there I regularly encounter continuously running, non-switchable un

Those are not ventilation systems. They are air conditioning units. You can’t compare the two. A mechanical ventilation system with heat recovery should be as quiet as a person breathing softly at a distance of three meters (10 feet).

Natural ventilation (windows plus air leak detectors) is not sufficient in an energy-efficient new build like yours to consistently ensure good air quality and moisture control. Air exchange strongly depends on wind and temperature, and with a tight building envelope, natural infiltration is minimal. Without heat recovery, this also results in heat energy losses. A controlled ventilation system or decentralized ventilation with heat recovery provides a consistent air exchange, regulates moisture and CO₂ levels, and saves energy.