KfW 55 - Ventilation system yes/no? - Experiences

  • Erstellt am 2020-05-19 13:29:21

exto1791

2020-05-27 10:40:29
  • #1


I know... There are just so many different opinions on the subject, which makes it incredibly difficult. I’m of the opinion: If I do it, then I do it right! (central system).

Either: yes: KFW 55 and ventilation Or no: KfW 70 and no ventilation. However, I also find this difficult because the airtightness of a KfW 70 hardly differs from that of a KfW 55 house and thus the mold problem doesn’t really decrease... But there are also quite a few builders who believe that you can easily ventilate a KfW 70 house yourself...
 

Tego12

2020-05-27 10:47:52
  • #2


First of all, calm down a bit..! If the system fails, no air will come into the house, and you won’t be able to breathe and will die. But seriously... if the system fails, it works exactly the same as for people without a ventilation system. Of course, something can break on a controlled residential ventilation system, but the technology is simple, I can’t think of a component even remotely in that price range... It consists more or less of 2 fans and a bit of electronics/sensors. You will definitely have to replace the system eventually, but we are probably talking more about 20 years rather than 10, ...

And yes, you can ventilate "without problems" yourself, but with controlled residential ventilation you don’t have to. I would never want to do without it anymore, no matter the type of construction. In my opinion, there is no greater comfort gain in a single-family house than a ventilation system.

On the topic of maintenance-intensive:
Photovoltaics: What maintenance?!
Heat pump: Air-water heat pump is definitely less maintenance-intensive in terms of frequency and costs than gas (no chimney sweep, no typical wear parts, …). Durability with good design at least equally long (poor design and very frequent cycling is of course the death of a heat pump, unfortunately this is often done completely wrong by the conservative gas/oil heating guys...), like current gas condensing boilers. For brine/water heat pumps certainly even longer, as it is a fairly constant energy source without major temperature fluctuations and no external unit.
 

exto1791

2020-05-27 10:52:52
  • #3
Very good answer, thank you!

Do you also have a central system? Are you also of the opinion: If already, then fully?
Disadvantages regarding dry indoor air, dust swirling around? How do you see that? Experiences?
 

Tego12

2020-05-27 11:01:30
  • #4
Yes, a decentralized system has no place in a new building, there are basically only disadvantages (many holes in the wall, louder, I have never heard of an enthalpy heat exchanger there either, …). The controlled residential ventilation does not dry the air, but pulls in the dry air from outside, and due to the large air exchange, the air inside the house is correspondingly drier when the outside air is dry.

Solution 1: Enthalpy heat exchanger, which has a certain moisture recovery (but does not necessarily have to be sufficient, but increases the room humidity by several percent)
Solution 2: Proceed as homeowners without controlled residential ventilation do. Turn off the system (would not be a solution for me) or reduce the air volume a little in winter.
Solution 3: Actively humidify.

Personally, I prefer a combination. I consider enthalpy heat exchangers an absolute must, it already helps without any disadvantages (in addition, you save yourself a possible preheating register, as icing is almost excluded with an enthalpy heat exchanger). In addition, I have a humidifier in an exhaust room, which humidifies the air and the system distributes it through the enthalpy heat exchanger in the house (but this is only necessary for a few weeks a year when it is really cold and the air outside is dust-dry). I do not want to reduce the controlled residential ventilation, because I enjoy the fresh air that is in the house at all times, e.g. in the morning right after waking up.

Regarding dust: You have less dust because much less comes in! The air goes through filters, with normal window openings everything comes in that is just swirling around, including insects. This is also another advantage of controlled residential ventilation, significantly fewer insects in the house in summer, since there is no direct need to throw all windows wide open because the air in the house is not so great.
 

exto1791

2020-05-27 11:05:37
  • #5


KfW 55 surcharge + central system with enthalpy heat exchanger for 18k possible? How high were your costs?
 

Tego12

2020-05-27 11:08:36
  • #6


To be honest, no idea, as it was planned in my fixed price from the beginning. I have a Zehnder Q350 myself, but the surcharge for the enthalpy heat exchanger was definitely below €1,000.
 

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