ᐅ KfW 70 without a ventilation system

Created on: 11 Feb 2011 09:40
D
Diin
Hello everyone,

maybe someone here can give us a good tip, as we are quite uncertain about a ventilation system.
We are planning to build a house (solid construction) according to KfW 70 standards, with underfloor heating, a fireplace, and a solar system. That much is already decided.

We received an offer from Company A for a ventilation system with heat recovery, and the salesperson recommended it to us.

At Company B, the ventilation system is significantly more expensive, and the salesperson told us that since the house is so well insulated, moisture would not be an issue... where would it come from? The rest could be regulated by normal airing anyway.
(I also think he realized that his ventilation system would have blown our budget and now I worry that he advised us against it just for that reason!)

My husband and I are laypersons, but my instinct tells me that the better the house is insulated, the more problems I would have getting rid of moisture and stale air inside the house, right?
After all, a blower door test does show that there is very little air circulation.
Am I completely wrong?
We are a bit torn now, since such a system is not exactly cheap! But is it necessary, or just a nice extra?

Thank you very much for your help!
C
cuhnie
28 Apr 2014 13:55
Despite all the enthusiasm, you should not overlook the disadvantages of a mechanical ventilation system with heat recovery. These systems offer benefits such as fresh air, but also have drawbacks.
M
milkie
28 Apr 2014 14:01
The same applies to everything else: heating systems, flooring, fuel for vehicles, and so on. The pros and cons of ventilation systems have already been discussed here extensively. Everyone has to make the decision for themselves.

milkie
D
DerBjoern
28 Apr 2014 14:09
cuhnie schrieb:
Despite all the enthusiasm, you should not overlook the disadvantages of a controlled residential ventilation system. These systems do not only offer benefits in terms of fresh air.

The only disadvantage I know of is that a controlled residential ventilation system costs money...
Mycraft29 Apr 2014 09:46
I can only agree with that; when professionally installed and correctly sized, I am not aware of any additional disadvantages.
B
Bauexperte
30 Apr 2014 11:39
Hello,
Mycraft schrieb:
I can only agree with that; with professional installation and correct sizing, I am not aware of any further disadvantages

The following information is taken from an energy consultation, so it cannot be said again that I am speaking badly of this system. Similar statements are also made by consumer protection agencies.

**On average, we spend 21.6 hours per day indoors and breathe 18,000 liters of air. In well-insulated and airtight residential buildings (renovated buildings, low-energy houses, etc.), a minimum air exchange rate of 0.1 1/h can occur. This corresponds to an air exchange rate of, for example, only 15 m³/h in a 60 m² (645 sq ft) apartment. However, DIN 1946-6 “Ventilation of residential buildings...” requires a minimum value of 60 m³/h for this type of residential unit. Buildings sealed this way must then be supplied by the occupant either by window ventilation with a sufficient airflow or by a controlled mechanical ventilation system with heat recovery.

Advantages
  • Preservation of health and building structure
  • Energy savings through controlled ventilation with heat recovery
  • Automatic fresh air supply (no window ventilation)
  • No drafts or noise from air movement
  • Removal of pollutants (to some extent), stale air, and moisture
  • Prevention of mold growth
  • Noise protection

Disadvantages
  • Not necessarily recommended for fresh air enthusiasts
  • The low fresh air volumes usually do not meet hygiene requirements
  • The building must be constructed as airtight as possible
  • For air circulation, door gaps are necessary
  • Transmission of airborne noise (through door gaps)
  • Retrofit in older buildings is relatively complex
  • Additional costs for system technology

**Source: Engineering Office Schreiner

For me personally—and this is off-topic—a controlled mechanical ventilation system with heat recovery is a no-go simply because it restricts/encloses me in my own home. I am certainly not willing to spend thousands of euros for this effect.

Regards, Bauexperte
D
DerBjoern
30 Apr 2014 11:51
Bauexperte schrieb:

  • Not necessarily recommended for fresh air enthusiasts

For fresh air enthusiasts, these systems are actually great!
  • The low fresh air volumes usually do not meet hygiene requirements

Where does that claim come from?
The building must be constructed as airtight as possible

That’s basically the goal nowadays anyway.
  • Door gaps are necessary for air circulation

That is a possible solution for most systems, yes.
  • Retrofit in older buildings is relatively complex
  • Additional costs for the system technology

As mentioned before, a controlled ventilation system simply costs more money, yes…
Personally — and off topic — a controlled ventilation system with heat recovery is a no-go for me just because it restricts/confines me in my own home. I would never spend thousands of euros for that effect.

I don’t see how our controlled ventilation system restricts or confines me at all!

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