ᐅ KFN House Without a Ventilation System – Experiences

nordanney schrieb:

Explain to the original poster what your ventilation concept looks like.

Occasionally open the windows.

nordanney schrieb:

The heating system does not matter. The stuffy air doesn’t care whether it is warmed by gas, heat pump, underfloor heating, or radiators.

The “stuffy air,” as you call it, doesn’t care. However, the heating system does affect how much energy you lose when ventilating. Convection-based systems are more prone to energy loss than radiant heating systems.

nordanney schrieb:

Room size does not matter either.

You are underestimating the impact of air volume. The smaller the air volume, the faster each person’s contribution to stuffiness becomes noticeable.

nordanney schrieb:

A bedroom in a modern house is always a “problem” at night, for example.

That is something special in our case: We do not have a bedroom, but rather a “multi-purpose room” that truly lives up to its name.

Besides, the choice of materials in a room is also a factor that can emphasize or reduce stuffiness. (And I am NOT talking about the much-debated “breathable” walls.)

Since you probably don’t measure CO2 or VOC levels, you have likely just gotten used to the stuffy air or ventilate manually six times a day.

RotorMotor schrieb:

Since you probably don’t measure CO2 or VOC levels, you’ve likely just gotten used to the stale air or you manually ventilate six times a day.

Where you are correct: We do not measure.
Where you mention a known effect: People are less sensitive to their own body odor than to unfamiliar smells.
Where you are mistaken: The assumed necessary ventilation frequency.
I assume you are starting from incorrect assumptions. Try to fully stale a space with over 300m³ (approximately 10,600 ft³) of room volume, occupied by two people, with wood or clay plaster surfaces that regulate moisture (in areas without windows), within one day.

We have a somewhat similar living situation to @wiltshire and previously lived in two different houses (both with a similar open-plan design) without mechanical ventilation with heat recovery (MVHR). Even though I currently have MVHR in this house, it is simply not as extreme as it is sometimes described here. As always, context is crucial, and two people (sometimes only one during the day) in such a large space do not produce anything I would even remotely call stale air. Because of this concern, we have such a measuring device running, and in fact, we could live here without MVHR without ending up with mold problems or suffocating from stale air.

One issue I would have is, in my opinion, nowadays overheated rooms, which I read about here occasionally, or the uniform temperature everywhere in all rooms, which feels somewhat artificial to me, for example.

As I said, I have MVHR and would choose it again, but I have tested it repeatedly and could live without MVHR under our particular circumstances—our individual situation!

In a "normal" single-family home with many small rooms and as many occupants, I would see it differently; ventilating would also be a major effort. Here, for example, I have also equipped the windows so that I can open them at the push of a button to ventilate.

I know people who open their windows just as often despite having MVHR because their instincts demand it, and they subconsciously cannot fully trust the effect of MVHR; if you have been used to that all your life, I can understand it. That was also my concern, but now I can sit inside with the windows closed and still feel the sensation of fresh air.

We find the mechanical ventilation with heat recovery very comfortable. Of course, we still air out occasionally (for example, after frying steaks). Otherwise, it does its job really well. Bathrooms dry quickly after showering. The fresh air is wonderfully preheated in winter. Since we installed split air conditioning units (we have enough electricity in summer), we no longer use the bypass because the heat exchanger also keeps the heat outside. I don’t want to be without it anymore – and the additional cost for us was 8,000 euros. I’d rather invest in better bathroom fixtures than save here.

sysrun80 schrieb:

We find the mechanical ventilation with heat recovery very comfortable. Of course, we still ventilate manually sometimes (for example, after frying steaks). Otherwise, it does its job really well. Bathrooms dry quickly after showering. The fresh air is wonderfully preheated in winter. And since we installed split air conditioning units (in summer we have enough electricity), we no longer use the bypass because the heat exchanger also keeps the heat outside. I don’t want to live without it anymore – and the extra cost for us was 8,000 euros. I’d rather invest in the bathrooms myself than save money here.

We have the same setup, and additionally, for the rare times I fry food, I always go out to the terrace to my grill, even in winter. As I said, I would do it the same way again; I don’t find a simple yes or no very helpful. Ultimately, what matters is whether you feel comfortable.