ᐅ Decentralized vs. Centralized Controlled Residential Ventilation: Considerations for KfW House Calculations
Created on: 6 Apr 2012 09:22
M
mirage
Good morning everyone,
we, 30LJ and 27LJ, are currently planning our two-story house as a KfW 70 standard with approximately 140 sqm (1,507 sq ft). From the forum and various sales discussions, we have become aware that new houses, especially those built to KfW standards, tend to be quite airtight.
Now we have the question about ventilation. The seller offered us an inverter-controlled mechanical ventilation system for about 7,730.00 EUR. After some research here in the forum as guests and also via Google, I found that there are also central controlled mechanical ventilation systems. This seems to be the better option to us, since you don’t have noisy fans in every room as is the case with decentralized systems. Furthermore, you don’t have holes in every insulated wall.
In advance, I looked at the Zehnder ComfoAir 350 system as a central controlled mechanical ventilation. There seem to be good opinions about it, and compared to the Hoval HomeVent RS 250, it is more affordable. Now my question is whether this is the right choice, or if it might be possible to do without a controlled mechanical ventilation system in a KfW 70 house at all? Also, I am unsure whether, if a ventilation system is necessary, a decentralized or central controlled mechanical ventilation system would be better. There are so many factors to consider, and the salespeople tend to just tell you what you want to hear, partly trying to sell their own products.
In addition, I wonder whether a controlled mechanical ventilation system with heat recovery could improve the rating of a KfW house. In other words, without controlled mechanical ventilation with heat recovery, it would be KfW 70; with controlled mechanical ventilation plus heat recovery, could it become KfW 55?
For primary energy, we are using district heating, which the city produces with a primary energy factor of 0.11. No solar, no geothermal, etc.
I would appreciate many responses.
Best regards
mirage
we, 30LJ and 27LJ, are currently planning our two-story house as a KfW 70 standard with approximately 140 sqm (1,507 sq ft). From the forum and various sales discussions, we have become aware that new houses, especially those built to KfW standards, tend to be quite airtight.
Now we have the question about ventilation. The seller offered us an inverter-controlled mechanical ventilation system for about 7,730.00 EUR. After some research here in the forum as guests and also via Google, I found that there are also central controlled mechanical ventilation systems. This seems to be the better option to us, since you don’t have noisy fans in every room as is the case with decentralized systems. Furthermore, you don’t have holes in every insulated wall.
In advance, I looked at the Zehnder ComfoAir 350 system as a central controlled mechanical ventilation. There seem to be good opinions about it, and compared to the Hoval HomeVent RS 250, it is more affordable. Now my question is whether this is the right choice, or if it might be possible to do without a controlled mechanical ventilation system in a KfW 70 house at all? Also, I am unsure whether, if a ventilation system is necessary, a decentralized or central controlled mechanical ventilation system would be better. There are so many factors to consider, and the salespeople tend to just tell you what you want to hear, partly trying to sell their own products.
In addition, I wonder whether a controlled mechanical ventilation system with heat recovery could improve the rating of a KfW house. In other words, without controlled mechanical ventilation with heat recovery, it would be KfW 70; with controlled mechanical ventilation plus heat recovery, could it become KfW 55?
For primary energy, we are using district heating, which the city produces with a primary energy factor of 0.11. No solar, no geothermal, etc.
I would appreciate many responses.
Best regards
mirage
Hi Mirage,
one small but possibly important remark: According to DIN standards, airtight houses must/should be ventilated 12 times a day! This value is probably the upper limit and the optimum; ventilating just a little twice a day is certainly not enough.
Maybe the experts here can provide a more realistic figure?
Best regards
Peter
one small but possibly important remark: According to DIN standards, airtight houses must/should be ventilated 12 times a day! This value is probably the upper limit and the optimum; ventilating just a little twice a day is certainly not enough.
Maybe the experts here can provide a more realistic figure?
Best regards
Peter
PeterXYZ schrieb:
... According to DIN standards, airtight houses must/should be ventilated 12 times a day! Which DIN standard?Best regards
Good morning, everyone,
I’m glad for your active participation. Whew, ventilating 12 times a day, and with cross-ventilation on top of that—I honestly can’t manage that. Even twice a day will be really challenging...
Edit:
I still wonder whether a mechanical ventilation system with heat recovery counts in the energy performance calculation.
I’m glad for your active participation. Whew, ventilating 12 times a day, and with cross-ventilation on top of that—I honestly can’t manage that. Even twice a day will be really challenging...
Edit:
I still wonder whether a mechanical ventilation system with heat recovery counts in the energy performance calculation.
€uro schrieb:
Which DIN standard?
Kind regards."A ventilation rate of 0.5 air changes per hour is required in living spaces (DIN 4108-2 from 2011, section 4.2.3). If there are no noticeable odors in the apartment, insufficient ventilation often manifests as excessively high indoor humidity" (Wikipedia).
0.5 air changes per hour correspond to 12 complete air changes per day.
Best regards
... does anyone have knowledge about calculating the air exchange rate? On one hand, air quality is important; on the other hand, especially for the house (mold), the humidity is crucial.
Humidity and poor air quality mostly occur when people are present, right? It seems illogical to me that the house should be ventilated just as often during absence or vacation as when people are at home! Are there any opinions on this?
Humidity and poor air quality mostly occur when people are present, right? It seems illogical to me that the house should be ventilated just as often during absence or vacation as when people are at home! Are there any opinions on this?
mirage schrieb:
...I still wonder whether a mechanical ventilation system with heat recovery plays a role in the energy calculation. Absolutely! That’s why the thermally active airflows must be taken into account, for example, in the heating load calculation. The better a building is insulated, the more noticeable and sustainable the impact of heat recovery becomes.Best regards
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