ᐅ Controlled residential ventilation with heat recovery — a confusing topic?
Created on: 13 Sep 2014 07:14
V
Voki1
Hello dear forum members,
We are—more or less—at the stage of choosing the general contractor, and now the question of installing a controlled mechanical ventilation system with heat recovery has come up again, even though we had initially decided against it for ourselves.
An appointment with a building expert from the Homeowner Protection Association really challenged my views and reopened the question of whether we need such a system at all.
Just to preempt some of the typical forum assumptions: yes, I have spent a day and a half on this forum and elsewhere absorbing information like crazy. I’m probably wiser, but still not ready to make a decision. It can’t be that I have to roll dice or flip a coin here.
I would really be interested in concrete arguments for why one might be able to do without such a system. For a controlled mechanical ventilation system with heat recovery (Pedotherm / Vaillant), we would have to pay nearly 10,000 euros. That’s quite a chunk. The general contractor did not push for it but clearly said it is not absolutely necessary (if you ventilate really well). However, in our case, there is practically no one home between about 7 a.m. and 4 p.m. That would be rather disadvantageous, especially in the first years of the new build, because window ventilation would naturally be reduced during those hours.
Man, this is quite frustrating when you feel so uncertain. Could you please help provide some reassurance?
We are—more or less—at the stage of choosing the general contractor, and now the question of installing a controlled mechanical ventilation system with heat recovery has come up again, even though we had initially decided against it for ourselves.
An appointment with a building expert from the Homeowner Protection Association really challenged my views and reopened the question of whether we need such a system at all.
Just to preempt some of the typical forum assumptions: yes, I have spent a day and a half on this forum and elsewhere absorbing information like crazy. I’m probably wiser, but still not ready to make a decision. It can’t be that I have to roll dice or flip a coin here.
I would really be interested in concrete arguments for why one might be able to do without such a system. For a controlled mechanical ventilation system with heat recovery (Pedotherm / Vaillant), we would have to pay nearly 10,000 euros. That’s quite a chunk. The general contractor did not push for it but clearly said it is not absolutely necessary (if you ventilate really well). However, in our case, there is practically no one home between about 7 a.m. and 4 p.m. That would be rather disadvantageous, especially in the first years of the new build, because window ventilation would naturally be reduced during those hours.
Man, this is quite frustrating when you feel so uncertain. Could you please help provide some reassurance?
Kisska86 schrieb:
We are building a solid structure with a brick facade, so without external thermal insulation composite system (ETICS). That way, our house still "breathes" a bit, which was important to us. Since I have a neighbor who argues similarly and, out of politeness, I don’t want to ask him directly:
The airtightness requirements for buildings apply regardless of the chosen wall construction. So why should your house still "breathe"?
And how does your house "breathe" away the CO2 and other air pollutants?
It may be true that some moisture buffering is possible depending on the interior plaster and wall structure — but what happens to the moisture in the wall if it is not ventilated or not sufficiently removed? At some point, the wall will become saturated. And natural cross-ventilation through gaps is basically not allowed anymore due to energy-saving regulations, right?
Maybe someone here can help clarify this for me...
I somehow feel that some people expect too much from the marketing claims of "red lime plaster"... but I’m also happy to learn more.
D
DerBjoern19 Sep 2014 10:43@Sattler
"Breathing" walls are a myth from the realm of dowsers. When walls "breathe," it usually means there is a serious construction defect, like holes in the structure.
Yes, moisture diffusion varies between different wall assemblies. However, this is irrelevant because the amount of moisture that can diffuse through walls is far too small to have any impact on indoor humidity levels.
The only way to remove moisture from a house is through ventilation.
"Breathing" walls are a myth from the realm of dowsers. When walls "breathe," it usually means there is a serious construction defect, like holes in the structure.
Yes, moisture diffusion varies between different wall assemblies. However, this is irrelevant because the amount of moisture that can diffuse through walls is far too small to have any impact on indoor humidity levels.
The only way to remove moisture from a house is through ventilation.
Hello,
I also believe that this should be done right away in a new build.
Our exterior walls are monolithic (meaning without external thermal insulation composite system), and still, we opted for decentralized ventilation.
You can find the pros and cons of central versus decentralized systems everywhere... for us, the deciding factor was the cost.
As already mentioned here, it costs about half as much.
In the utility room, technical room, and bathroom, we have exhaust fans, and in the other rooms, we have fans with heat recovery.
Because the fans are always running, the humidity inside the house stays around 55-65% (depending on the weather).
Humidity in new buildings is usually higher, so proper ventilation is especially important during the first years.
This is now taken care of automatically for us.
I also believe that this should be done right away in a new build.
Our exterior walls are monolithic (meaning without external thermal insulation composite system), and still, we opted for decentralized ventilation.
You can find the pros and cons of central versus decentralized systems everywhere... for us, the deciding factor was the cost.
As already mentioned here, it costs about half as much.
In the utility room, technical room, and bathroom, we have exhaust fans, and in the other rooms, we have fans with heat recovery.
Because the fans are always running, the humidity inside the house stays around 55-65% (depending on the weather).
Humidity in new buildings is usually higher, so proper ventilation is especially important during the first years.
This is now taken care of automatically for us.
@VillaMo How long have you been living in the house? The issue of humidity is interesting, especially during winter... I have heard it can get too dry then.
And how is the sound insulation?
In summary, when considering mechanical ventilation systems with heat recovery, you should think about the following (the list can be extended with bullet points) + = positive / - = negative / o = neutral
+ Fresh air, removal of pollutants from furniture, floors
+ Moisture from the construction is automatically removed
- Potentially increased noise transmission from outside (especially with decentralized systems)
- Possible odor nuisance from outdoor smells
- Possible dry air in winter
o Costs
o Maintenance (filter replacement)
And how is the sound insulation?
In summary, when considering mechanical ventilation systems with heat recovery, you should think about the following (the list can be extended with bullet points) + = positive / - = negative / o = neutral
+ Fresh air, removal of pollutants from furniture, floors
+ Moisture from the construction is automatically removed
- Potentially increased noise transmission from outside (especially with decentralized systems)
- Possible odor nuisance from outdoor smells
- Possible dry air in winter
o Costs
o Maintenance (filter replacement)
If there is a negative point in this list, it is clearly the costs, at least in the case of a centralized system.
I believe that without (central) mechanical ventilation with heat recovery, noise disturbance from outside is more problematic when windows are opened for ventilation.
Sound transmission through the system itself can be an issue, but it should not be, at least on the lower settings with proper installation (minimum duct length).
I believe that without (central) mechanical ventilation with heat recovery, noise disturbance from outside is more problematic when windows are opened for ventilation.
Sound transmission through the system itself can be an issue, but it should not be, at least on the lower settings with proper installation (minimum duct length).
We have only been living in the house for just under two months, so I cannot share any winter experience yet.
Regarding noise, you can hear a slight humming sound from the fan. However, we do not find it disturbing. Depending on the manufacturer, there are also sound insulation kits available that can be installed additionally. The fan’s position also seems to affect the noise level, so it is important to ensure it is installed in a suitable location. I read this in a brochure from our fan manufacturer.
Occasionally, you can hear faint noise from outside, but so far we do not find it bothersome. I guess this also depends on the location of the house (quiet area or not). Possibly, this can be further reduced with such sound insulation kits.
Regarding noise, you can hear a slight humming sound from the fan. However, we do not find it disturbing. Depending on the manufacturer, there are also sound insulation kits available that can be installed additionally. The fan’s position also seems to affect the noise level, so it is important to ensure it is installed in a suitable location. I read this in a brochure from our fan manufacturer.
Occasionally, you can hear faint noise from outside, but so far we do not find it bothersome. I guess this also depends on the location of the house (quiet area or not). Possibly, this can be further reduced with such sound insulation kits.
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