ᐅ Building a Single-Family Home in North Rhine-Westphalia

11ant schrieb:
Blind control of the blinds, please, without technical gimmicks, but when replacing analog window ventilation, it can be helpful. I don’t have to understand everything.

Controlled mechanical ventilation saves 30-50 minutes per day. A perfectly adjusted window automation system, which always does exactly what I want without switches, remote controls, or apps, saves at most 1 minute. An imperfect automation actually wastes time.
That doesn’t mean it can’t be done. Steffen spends 80,000 EUR on his automation. That’s possible if you want to. In our opinion, this is where “reasonable” ends. At least, that's our opinion. Others may see it differently.

I clean my windows much more often than every ten years, and a fly screen in high summer is enough air filtration for me.

Good for you. Fly screens and F7 filters have nothing to do with each other.

I do appreciate that in a mechanically ventilated house, the indoor air is significantly cleaner than outside air. The fine dust/diesel/ direct injection problem will remain with us for at least two decades and it has already been proven that fine dust damages lungs and heart — basically like smoking yourself. Being shielded for at least half of the day, which you spend inside your house, is a good thing.

The filters should also be changed much more often than every 10 years. Several times a year, possibly quarterly. That’s where all the dirt collects, which did not enter the house but was filtered out. And a lot collects there. You have to consider that otherwise all of that would be inhaled.

And the exposure to VOCs, formaldehyde, and so on is invisible but still present. Just because you don’t see it doesn’t mean it isn’t harmful. Didn’t a user just compare this to radioactivity?

To avoid getting fully involved in this fundamental debate (which has already been discussed multiple times in this forum) and to possibly give the thread starter some guidance:

I have had the same discussions, but they didn’t help me with my question because I still don’t know which “camp” is actually correct. For that, I spent countless hours on Google.

What I am about to say comes from the knowledge I gained through that very research, based on other people’s statements, what my mind retained, and what my intuition tells me. Everyone who supports mechanical ventilation with heat recovery has one themselves and has confirmed their experience after years (“never again without” is a common phrase). Those who argue against it almost always do not have mechanical ventilation.

I have read this many times, and my heating engineer also explained it to me independently, and physically it seems logical: For mold and germ growth, moisture is needed on or inside the pipes. For moisture from the air to stick to the pipe surface (condensation), the so-called dew point must be fallen below. This can happen, for example, when humid indoor air at 21°C (70°F) flows through pipes located in an unheated/insulated part of the house (such as an attic). This could cause the dew point (roughly 8-15°C (46-59°F), I believe) to be undershot, resulting in condensation. If this does not happen, nothing occurs. Like clothes in the wind (pipe inner surfaces in the airflow), these surfaces are more likely to dry than become wetter (the pipes are actually dried).

All kinds of guides, at least those from the KfW, all craftsmen I spoke to, and especially house builders (who want to sell) say that in modern houses with airtight building envelopes, moisture must be removed. How this is done in the end (by manual ventilation, mechanical ventilation with heat recovery, passive window ventilation) does not matter, as long as it works.

It is also true that moisture only develops where it is generated. Primarily, this is from people themselves. Then there is cooking, wet laundry, and showering. Unused rooms that remain unheated might face dew point problems again. Where you actually live, you can also ventilate. But honestly, do you really do that? If so, that’s good.

I am somewhat surprised that not even one of the experienced owners has had a germ test done after several years and shared the results, as it would be a strong argument from the experience of several owners and in their own interest. Correct me if I’m wrong, but apart from minor comments, I haven’t found anything.

Grym schrieb:
As long as the filter is changed quarterly (also use exhaust air filters!)

What do you mean by exhaust air filter? We have filters both on the supply air and in the Zehnder ComfoAir Q.

Grym schrieb:
Steffen is spending 80,000 EUR on his automation. You can do that if you want. In our opinion, that crosses the line of what’s “reasonable.” That’s just our opinion, of course. Others might see it differently.

That’s not really a strong argument though. For some, a car with 130 hp is already “too much,” while for others, it’s only “too much” at 300 hp. So basically, that says nothing. If I started listing everything our house controls and where it “thinks ahead” (security, burglary protection, fire safety, etc.), we could debate the sense or nonsense of it for a long time.

By the way, the 80,000 EUR doesn’t just cover automation but the entire electrical system. For a house our size, that alone would typically be around 20,000 EUR.

Regards, Steffen

Filters can be installed directly in the exhaust air vents. Any dirt remaining in the kitchen after the recirculation filter will not enter the ducts but will be trapped in this filter located right in the exhaust vent.

Of course, dirty exhaust ducts are generally not a problem, since when the system is running, the airflow always moves in one direction. However, it is also possible to equip the exhaust vents with filters and keep the ducts clean as well.

It is important that the system runs 24/7. Exhaust systems without a filter or with a broken filter that only operate on demand and remain off for 23 hours are indeed problematic from a hygiene perspective – but this has nothing to do with a controlled residential ventilation system. It would be like taking the experience of a moped rider in a large African city and concluding from that that driving a new Mercedes GLS on a German highway would be dangerous.

Grym schrieb:
Filters can be installed directly in the exhaust vents. Whatever dirt remains in the kitchen after the recirculation filter won’t enter the ducts but will be trapped in this filter right in the exhaust vent.

That’s the theory and perhaps the practice for some, but personally, I’m not convinced.
The activated carbon filters in recirculation mode tend to reduce airflow, making the system automatically louder. They probably don’t filter all odors and grease, and according to recirculating hood manufacturers, the hood must be regularly wiped inside (who actually does that? I suspect hardly anyone).
The carbon filter also needs regular replacement (once a year?), which might still be manageable.

An additional filter in the exhaust opening seems reasonable. But I don’t believe that nothing passes through it; however, the amount should be minimal.

From an energy perspective, exhaust hoods are a complete disaster. I am getting one at my own request anyway. Customer opinions on this topic are abundant online, and there are just as many supporters as opponents here as well.

Grym schrieb:
Filters can be installed directly in the exhaust vents. Whatever dirt remains in the kitchen after the recirculation filter won’t enter the ducts but will be trapped in this filter right in the exhaust vent.

Of course, dirty exhaust ducts are generally not a problem since the airflow always moves in one direction when the system runs. But filters can also be installed in the exhaust vents, and the ducts can be kept clean as well.

It’s important that the system runs 24/7. Exhaust systems with no or broken filters that only operate occasionally and are off 23 hours a day are actually a hygiene problem – but they have nothing to do with a mechanical ventilation with heat recovery (MVHR) system. That would be like taking a moped rider in a large African city and concluding from that that driving a new Mercedes GLS on a German highway would be dangerous.

I completely agree with you.

Grym schrieb:
Filters can be installed directly in the exhaust vents. Any dirt remaining in the kitchen after the recirculation filter does not enter the ducts but stays in this filter located directly in the exhaust vent.

I think I mixed up supply air with exhaust air. How do you get filters where the used air is "extracted"? Where fresh air comes into the room, there are no filters. That’s correct, right?