ᐅ Controlled residential ventilation & heat pumps: Viessmann vs. Vaillant vs. Zehnder?
Created on: 23 Nov 2022 14:12
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Nixwill2Hello everyone,
I want to revisit a topic that was mentioned a while ago in another thread but deserves a more detailed discussion, as it turns out to be more complicated than anticipated. Here’s our situation, and I would really appreciate hearing about your experiences. Starting with the background.
We are currently building a prefabricated house (timber construction) with a prefab home manufacturer. The plot is located in a small village, in a very old part of town. It seems like almost everyone heats with wood there. On our property, there is a wood smoke smell throughout the entire winter (we noticed this last year already, and it’s happening again this year), as if there is a campfire burning nearby non-stop.
Now, we are seriously concerned that with a mechanical ventilation system with heat recovery (MVHR), the indoor air could end up smelling the same as the outdoor air, which we definitely want to avoid. To counter this, we thought about installing a mechanical ventilation system with an activated carbon filter included. That’s why we have tentatively selected the Zehnder ComfoAir Q350 TR in the enthalpy version, since both of us already occasionally suffer from dry eyes. This system also comes from the factory with attachments for activated carbon filters.
Unfortunately, things turned out differently than expected. The house supplier is hesitant in initial discussions and is postponing the topic until the customization meeting in December. The reason given: they only work with Viessmann or Vaillant because the heat pumps come from those manufacturers. More precisely, it would be either the Viessmann Vitovent 300W or the Vaillant recoVair VAR360 ventilation system. Neither of these original systems offers a solution with an activated carbon filter.
Now to my main question. What’s your opinion on this? Our concern is not unfounded, and an F7 pollen filter doesn’t seem to be an adequate solution for this situation, does it? They immediately said that an F7 filter would be sufficient, but we don’t believe that.
Is it possible to install a Zehnder mechanical ventilation system alongside a heat pump from Viessmann or Vaillant, or not?
I don’t want to assume the worst-case scenario, but do you have any ideas on how to solve this problem if the house provider doesn’t allow any other mechanical ventilation system?
I would be very grateful for any ideas, experiences, or tips!
Best regards
I don’t know the exact amount off the top of my head, but it’s over €10,000.
I’m just not sure how this works with a prefabricated house. Installing the piping inevitably involves another trade, so if something goes wrong later, I suspect each party will blame the other...
I’ll just bring it up when we’re there and see how they respond.
Last night, I did some more reading and tried out different calculation methods, but I’m giving up on that—I’ll leave it to the professionals because the results vary so much. The differences are so significant that I want to see the calculations and planning from the house builder first.
I entered the entire house into AIRplan. There were a few checkboxes I didn’t understand, but the differences were minimal to none. These were the airflow values I got:
Reduced ventilation: 146 m³/h (86 cfm)
Nominal ventilation: 209 m³/h (123 cfm)
Intensive ventilation: 272 m³/h (160 cfm)
On an Austrian website "xxx.komfortlüftung.xx" there is also a sizing guide, but these values came up for our case:
Minimum device airflow: 123 m³/h (72 cfm)
Operating airflow: 306 m³/h (180 cfm)
Maximum device airflow: 429 m³/h (252 cfm)
In every case, the assumption was the entire house size including all usable areas and cellar rooms, roughly 235 m² (2,530 ft²).
At least from AIRplan, I now understand how the distribution of the valves works; their schematic was quite interesting and also explains the number of valves in our contract. The builder only included the two heated cellar rooms in the cellar, matching our previous assumption regarding the cellar volume in cubic meters. If we want to include the other cellar rooms as well, that would definitely increase the cost again...
How is this usually handled in an unfinished concrete cellar? Do the pipes run along the ceiling and do holes need to be drilled into the walls?
I’m just not sure how this works with a prefabricated house. Installing the piping inevitably involves another trade, so if something goes wrong later, I suspect each party will blame the other...
I’ll just bring it up when we’re there and see how they respond.
Last night, I did some more reading and tried out different calculation methods, but I’m giving up on that—I’ll leave it to the professionals because the results vary so much. The differences are so significant that I want to see the calculations and planning from the house builder first.
I entered the entire house into AIRplan. There were a few checkboxes I didn’t understand, but the differences were minimal to none. These were the airflow values I got:
Reduced ventilation: 146 m³/h (86 cfm)
Nominal ventilation: 209 m³/h (123 cfm)
Intensive ventilation: 272 m³/h (160 cfm)
On an Austrian website "xxx.komfortlüftung.xx" there is also a sizing guide, but these values came up for our case:
Minimum device airflow: 123 m³/h (72 cfm)
Operating airflow: 306 m³/h (180 cfm)
Maximum device airflow: 429 m³/h (252 cfm)
In every case, the assumption was the entire house size including all usable areas and cellar rooms, roughly 235 m² (2,530 ft²).
At least from AIRplan, I now understand how the distribution of the valves works; their schematic was quite interesting and also explains the number of valves in our contract. The builder only included the two heated cellar rooms in the cellar, matching our previous assumption regarding the cellar volume in cubic meters. If we want to include the other cellar rooms as well, that would definitely increase the cost again...
How is this usually handled in an unfinished concrete cellar? Do the pipes run along the ceiling and do holes need to be drilled into the walls?
Dogma schrieb:
I wouldn’t skip the basement if you’re building new anyway. You can’t hide the ventilation ducts any better than there.
I don’t want to contradict you because I honestly don’t know much and might be missing something, but isn’t ventilation in the basement kind of overkill when it comes to cost-effectiveness?
Of course, a whole-house mechanical ventilation system, including the basement, would be a “comfort gain.” At the same time, operating it costs money, and personally, I would want to save on running the system constantly in rooms you hardly ever use. Especially since those rooms are probably heated differently, which would reduce the efficiency of heat recovery there.
I have also been thinking about this topic, especially since we initially want to use the two heated basements as "cold" basements. However, since they are already included in the offer and will hopefully prevent moisture problems, we would prefer to keep them planned as is for now.
My idea was whether it might be possible to manually open and close the valves in the basement, depending on usage. Could something like that be done? Ideally, it would also be possible to keep the flow running at a minimum moisture protection level. I have no idea if this is standard practice...
My idea was whether it might be possible to manually open and close the valves in the basement, depending on usage. Could something like that be done? Ideally, it would also be possible to keep the flow running at a minimum moisture protection level. I have no idea if this is standard practice...
Nixwill2 schrieb:
I don’t know the exact amount off the top of my head, but it’s over €10,000.
I’m just not sure how it works with a prefabricated house. Laying the ductwork inevitably involves a different trade, so if something goes wrong later, I imagine each party would blame the other...
I’ll just bring it up when we’re there and see how they react.
Last night I did some more reading and tried different calculation methods, but I’m giving up on that; I’d rather leave it to the experts because the results vary so much that I want to see the calculations and plans from the builder first.
I entered the entire house into AIRplan. There are a few options I don’t understand, but the differences were small or negligible. These were the airflow values:
Reduced ventilation: 146 m³/h (86 cfm)
Nominal ventilation: 209 m³/h (123 cfm)
Intensive ventilation: 272 m³/h (160 cfm)
On an Austrian website "xxx.komfortlüftung.xx" there is also a sizing aid, which gave these values for us:
Minimum device airflow rate: 123 m³/h (72 cfm)
Operating airflow rate: 306 m³/h (180 cfm)
Maximum device airflow rate: 429 m³/h (252 cfm)
The assumption was the total house size, including all usable areas and the basement, roughly 235 m² (2,530 ft²).
Thanks to AIRplan, I at least now understand how the vents are distributed. Their scheme was quite interesting and explains the number of vents in our contract. The builder only included the two heated basement rooms, which matches our previous assumption about the basement volume. Including the other basement rooms would certainly lead to significantly higher costs...
How is this usually done in an unfinished concrete basement? Are the ducts run along the ceiling and holes drilled into the walls for the vents? Well, actually that’s not a problem. You just need to specify the total airflow and the airflow per room. Then give the requirement that air velocity should be 3 to 3.5 m/s (10 to 11.5 ft/s) in the duct and 1 to 1.5 m/s (3.3 to 5 ft/s) at the ceiling diffusers. Based on that, they can calculate the appropriate duct dimensions and the number of ceiling diffusers needed per room.
For the basement, they usually make an opening in the ceiling and install a drywall box where the diffusers sit (but please not right next to the door :p).
netuser schrieb:
I’m not trying to contradict you because I don’t really know much and probably miss something, but isn’t ventilating the basement overkill in terms of cost-effectiveness?
Of course, controlled mechanical ventilation throughout the whole house, including the basement, is a “comfort gain.” At the same time, it costs money to operate, and personally, I’d prefer to avoid running the system continuously in rooms I hardly ever use. Especially since those rooms are probably heated differently, which might reduce the efficiency of heat recovery? I understand what you mean, but usually, in the basement, you only need airflow for moisture control, so in this case, that would be 0.3 to 0.5 (0.5 if you occasionally use the basement for laundry or parties) times 73 m³ (2,577 ft³). This airflow of max. 36.5 m³/h (21.5 cfm) can easily be provided by the system and costs maybe €5 more per year in electricity.
Regarding the cost of installing the ductwork (see above), honestly, I’d rather spend an extra €1,000 on something that actually adds value than €1,000 more on an entrance door that looks wooden instead of white but doesn’t add any real benefit except a different look.
Unfortunately, when building, savings are often made in the wrong places or priorities are misplaced.
@Dogma
Could you maybe share a few thoughts on the values I mentioned?
I also entered the house data into Helios just now and got almost identical results to AIRplan:
Reduced ventilation: 148 m3/h (87 cfm)
Nominal ventilation: 212 m3/h (125 cfm)
Intensive ventilation: 275 m3/h (162 cfm)
The recommendation was also for a 500 m3/h (294 cfm) unit, just as you suggested.
How is the unit size determined here? (I once read something about nominal ventilation x 2, is that roughly correct?)
The values were determined according to DIN standards, probably why the results are so similar to AIRplan. Can you explain the Austrian deviation (do you even know their methodology)?
Could you maybe share a few thoughts on the values I mentioned?
I also entered the house data into Helios just now and got almost identical results to AIRplan:
Reduced ventilation: 148 m3/h (87 cfm)
Nominal ventilation: 212 m3/h (125 cfm)
Intensive ventilation: 275 m3/h (162 cfm)
The recommendation was also for a 500 m3/h (294 cfm) unit, just as you suggested.
How is the unit size determined here? (I once read something about nominal ventilation x 2, is that roughly correct?)
The values were determined according to DIN standards, probably why the results are so similar to AIRplan. Can you explain the Austrian deviation (do you even know their methodology)?
Maybe, if possible, get the contact information of the heating installer. I also spent a lot of time beforehand figuring out what would be best. I read datasheets, watched videos, and so on.
Two weeks ago, I had the initial consultation with him and shared my preferences. Two days later, he called me to inform me that the delivery times are over a year. The foundation slab is currently being poured. A year is way too long since the screed needs to be dried within 6 months. Waiting for half a year without progress is not worth it for me.
In the end, it became a Vaillant system because only they could deliver "soon."
That means it’s quite possible you’ll just have to accept whatever you can get.
Two weeks ago, I had the initial consultation with him and shared my preferences. Two days later, he called me to inform me that the delivery times are over a year. The foundation slab is currently being poured. A year is way too long since the screed needs to be dried within 6 months. Waiting for half a year without progress is not worth it for me.
In the end, it became a Vaillant system because only they could deliver "soon."
That means it’s quite possible you’ll just have to accept whatever you can get.