ᐅ Decentralized vs. Centralized Controlled Residential Ventilation: Considerations for KfW House Calculations
Created on: 6 Apr 2012 09:22
M
mirageGood 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,
a few comments from a layperson:
- The KfW calculation should improve significantly
- A decentralized system only makes sense if you want to ventilate specific (few) rooms
- It is more comfortable and better with a central controlled residential ventilation system – but you will have ducts throughout the house, costs, etc.
Best regards
a few comments from a layperson:
- The KfW calculation should improve significantly
- A decentralized system only makes sense if you want to ventilate specific (few) rooms
- It is more comfortable and better with a central controlled residential ventilation system – but you will have ducts throughout the house, costs, etc.
Best regards
Good morning PeterXYZ,
ah, yes, the decentralized system for a few rooms makes sense. The developer we are considering uses prefabricated concrete elements that are cast in a factory according to the plans. Does this make a difference when planning a central mechanical ventilation system with heat recovery?
Has anyone had experience with this?
Regards
mirage
ah, yes, the decentralized system for a few rooms makes sense. The developer we are considering uses prefabricated concrete elements that are cast in a factory according to the plans. Does this make a difference when planning a central mechanical ventilation system with heat recovery?
Has anyone had experience with this?
Regards
mirage
B
Bauexperte6 Apr 2012 11:13Hello,
Choosing a central mechanical ventilation system always makes sense; heat recovery is not necessarily required as it often costs more than it benefits. You gain a high level of comfort and especially in the first years—if the system is properly installed—you don’t have to worry about mold due to drying of the building. Furthermore, you can leave the house unattended peacefully—e.g., on vacation—without asking family or neighbors to ventilate for you; if your plants are in self-watering pots, you don’t need anyone to water your flowers either.
Kind regards
mirage schrieb:That is correct.
we (age 30 and 27) are currently planning our two-story house as a KfW 70 building with approximately 140sqm (1,507 sq ft). Through the forum and various sales talks, we have become aware that new houses, especially those built to KfW standards, tend to be quite airtight.
mirage schrieb:The fans in a decentralized ventilation system are anything but noisy; who says otherwise?
.... This seems better to us because you don’t have noisy fans in every room as with a decentralized system. In addition, there are no holes in the insulated walls in each room.
mirage schrieb:First of all, I can hardly imagine that you will have any significant influence over the brand to be installed; each supplier usually has their own preferences or contracts. What really matters is that the mechanical ventilation system is designed to meet the needs of the house, not the preferences of the provider.
Initially, I looked at the Zehnder ComfoAIR 350 system as a central mechanical ventilation with heat recovery. There are good reviews of it, and it is cheaper compared to a Hoval HomeVent RS 250.
mirage schrieb:The decision for a mechanical ventilation system with or without heat recovery should never be based on a few marginal values within energy saving regulations; that is mostly an illusion and happens almost exclusively on paper.
Now I wonder whether it is the right choice or if you can do without a mechanical ventilation system in a KfW70 house?! Also, if a mechanical ventilation system is necessary, should it be a decentralized or central version? There are so many things to consider, and salespeople mostly just tell you what you want to hear and try to sell their products. Furthermore, I wonder whether a mechanical ventilation system with heat recovery can improve the energy rating of a KfW house – for example, without one: KfW70, with mechanical ventilation + heat recovery = KfW55?
Choosing a central mechanical ventilation system always makes sense; heat recovery is not necessarily required as it often costs more than it benefits. You gain a high level of comfort and especially in the first years—if the system is properly installed—you don’t have to worry about mold due to drying of the building. Furthermore, you can leave the house unattended peacefully—e.g., on vacation—without asking family or neighbors to ventilate for you; if your plants are in self-watering pots, you don’t need anyone to water your flowers either.
Kind regards
Hello,
The cooler the climate location, the more effective the controlled residential ventilation with heat recovery becomes. Moreover, it is always sensible to consider the controlled residential ventilation in connection with the rest of the building services. The controlled residential ventilation with heat recovery can significantly reduce heating loads, which means that, for example, when using a heat pump as the heat source, often a unit with a smaller capacity can be selected. This saves several thousand euros, especially with a ground-source heat pump, since not only the unit but also the source becomes more affordable. This often offsets the additional cost for heat recovery and results in not just an investment saving.
Best regards
Bauexperte schrieb:I see this a bit differently. The real value of a controlled residential ventilation system lies in comfort and in the controlled ventilation. The cost difference between a central controlled residential ventilation system without heat recovery and one with heat recovery is not as significant as is often assumed.
...Choosing a central controlled residential ventilation system always makes sense; heat recovery is not necessarily required since it costs more than it is worth.
The cooler the climate location, the more effective the controlled residential ventilation with heat recovery becomes. Moreover, it is always sensible to consider the controlled residential ventilation in connection with the rest of the building services. The controlled residential ventilation with heat recovery can significantly reduce heating loads, which means that, for example, when using a heat pump as the heat source, often a unit with a smaller capacity can be selected. This saves several thousand euros, especially with a ground-source heat pump, since not only the unit but also the source becomes more affordable. This often offsets the additional cost for heat recovery and results in not just an investment saving.
Best regards
Hi,
thank you very much for all your numerous replies. It’s exactly as Bauexperte suspected. Both of us work full-time; I leave home at 5:00 AM and my partner at 5:30 AM, and we’re usually back around 4:20 PM. I’m a civil servant working 41 hours per week :-( and she also works in the public sector, so we’re never home earlier than that.
Our builder has more or less given us free rein—if I say I want the Zehnder ComfoAir 350 enthalpy system, then that’s what will be installed...
As confirmed earlier, we fear we won’t be too diligent about ventilation since no one is at home during the day, at least not yet. And when I think about airing out the house completely twice a day, I’m motivated only the first three weeks after moving in—after that, you just don’t feel like it because the day is already too short.
This is approximately how my day looks:
4:45 AM wake up
5:05 AM leave for work
6:00 AM work starts
3:30 PM work ends
4:30 PM home
5:15 PM exercise
6:45–7:00 PM home
9:00 PM go to sleep
My partner has a similar routine, except on Tuesdays when she has citizen consultations until 6:00 PM.
@Bauexperte,
I’ve read about the noise issue with decentralized mechanical ventilation (MVHR) systems both through various internet research and manufacturer datasheets—for example, the InVenter Twin has around 60 dB, which I find quite loud. My partner is particularly sensitive to high-pitched and humming noises. The price difference of about 1,500 euros for a central mechanical ventilation system seems reasonable considering this.
What other recommended German systems are there? Right now, controlled mechanical ventilation is very much on my mind, especially since I plan to live in this house for life (that’s the plan). Installing something later would only be a compromise and more expensive...
Best regards
mirage
P.S. No, I’m not a police officer :-)
thank you very much for all your numerous replies. It’s exactly as Bauexperte suspected. Both of us work full-time; I leave home at 5:00 AM and my partner at 5:30 AM, and we’re usually back around 4:20 PM. I’m a civil servant working 41 hours per week :-( and she also works in the public sector, so we’re never home earlier than that.
Our builder has more or less given us free rein—if I say I want the Zehnder ComfoAir 350 enthalpy system, then that’s what will be installed...
As confirmed earlier, we fear we won’t be too diligent about ventilation since no one is at home during the day, at least not yet. And when I think about airing out the house completely twice a day, I’m motivated only the first three weeks after moving in—after that, you just don’t feel like it because the day is already too short.
This is approximately how my day looks:
4:45 AM wake up
5:05 AM leave for work
6:00 AM work starts
3:30 PM work ends
4:30 PM home
5:15 PM exercise
6:45–7:00 PM home
9:00 PM go to sleep
My partner has a similar routine, except on Tuesdays when she has citizen consultations until 6:00 PM.
@Bauexperte,
I’ve read about the noise issue with decentralized mechanical ventilation (MVHR) systems both through various internet research and manufacturer datasheets—for example, the InVenter Twin has around 60 dB, which I find quite loud. My partner is particularly sensitive to high-pitched and humming noises. The price difference of about 1,500 euros for a central mechanical ventilation system seems reasonable considering this.
What other recommended German systems are there? Right now, controlled mechanical ventilation is very much on my mind, especially since I plan to live in this house for life (that’s the plan). Installing something later would only be a compromise and more expensive...
Best regards
mirage
P.S. No, I’m not a police officer :-)
Similar topics