Hello everyone,
we are building a KfW 70 house, which is economic even without a mechanical ventilation system.
Now, like many others, we are uncertain whether we really want to install a mechanical ventilation system. It has been planned, but the prices quoted are quite high... A decentralized system also seems to be similarly expensive due to the number of rooms and additionally causes quite a few holes in the nice facade...
Our heating engineer, who also installs ventilation systems, suggested installing fans in the exterior walls of the wet rooms (guest toilet and bathroom). These would be controlled by a switch and/or humidity sensors to extract the moist air from the rooms.
Additionally, a cooker hood with exhaust ventilation is recommended for the kitchen.
What do you think about this?
From a cost perspective, it does seem to be considerably cheaper.
we are building a KfW 70 house, which is economic even without a mechanical ventilation system.
Now, like many others, we are uncertain whether we really want to install a mechanical ventilation system. It has been planned, but the prices quoted are quite high... A decentralized system also seems to be similarly expensive due to the number of rooms and additionally causes quite a few holes in the nice facade...
Our heating engineer, who also installs ventilation systems, suggested installing fans in the exterior walls of the wet rooms (guest toilet and bathroom). These would be controlled by a switch and/or humidity sensors to extract the moist air from the rooms.
Additionally, a cooker hood with exhaust ventilation is recommended for the kitchen.
What do you think about this?
From a cost perspective, it does seem to be considerably cheaper.
Teufelchen1985 schrieb:
And even a decentralized system seems to be similarly costly due to the number of rooms and also creates quite a few holes in the nice facade…
Now the heating engineer, who also installs ventilation systems, suggested installing fans in the exterior walls for the wet rooms (guest toilet and bathroom), which are controlled by a switch and/or humidity sensors to extract the moist air from the room.
Additionally, a kitchen exhaust hood with extraction is recommended.
Hi,
until last week, we were also torn back and forth but were already leaning toward a decentralized system. Our general contractor also planned exhaust fans in the wet rooms (bathroom, shower room, kitchen, and utility room) as well as wall air vents, which are supposed to allow fresh air to flow in. We were quite uncertain.
Since signing the contract is approaching and we wanted clarity, we visited a ventilation office near Berlin last week. Of course, the consultant there wanted to sell something, but in my opinion, the consultation was fine and shed light on the situation.
The proposed concept:
The exhaust fans extract moist air from the wet rooms (the smaller fans circulate about 60 – 80 cubic meters of air per hour). They are controlled using a timer and possibly humidity sensors. Extracting the air creates negative pressure, which is balanced by fresh air drawn in through the wall air vents. So far, so good.
Issues:
1. Moisture is drawn out of the wet rooms. Once the humidity sensor detects that the set threshold has been reached, the fan turns off (possibly with a timer for delayed run-on). Other moisture, such as that generated just by people staying at home, is not extracted this way (aside from the occasional negative pressure). For example, at night when a person loses about 1 liter (1 quart) of fluid, this remains inside the house.
2. Fresh air only comes in when the fans are running. If they are off, there is little to no air circulation. So the “feel-good fresh air effect” hardly occurs. You could run the fans continuously—but then issue 3 comes into play.
3. The air drawn in through the wall vents is just regular outside air. In summer, that means warm air; in winter, cold air. On the one hand, sitting in a cold draft can be unpleasant; on the other hand, this air has to be heated. If you want the “feel-good fresh air effect” and run the fans continuously, you will constantly pull freezing cold outside air into the house during winter.
4. For allergy sufferers: exhaust fans pull air out. As far as I understand, pollen filters cannot be installed in the wall air vents (although I am not 100% sure). That means pollen will also be drawn into the house.
Kitchen extraction hood: You need to be careful about how powerful the exhaust hood is. Some hoods pull up to 700 cubic meters of air per hour. That air has to come from somewhere, so it is drawn through the wall vents (which can cause whistling in the worst case). (That is why Wastl also asked about the chimney, since in some cases smoke might not go up the chimney but be pulled through the apartment into the kitchen—this does not apply to you.) So, you should pay attention to how much air the extraction hood draws.
This is a layperson’s opinion. Perhaps the consultant was simply highly trained in salesmanship. But he relieved our uncertainty, so now we know what we will do. Others may see it differently.
What we will do:
Exhaust fans with timer and humidity sensors (60 – 80 cubic meters) in the bathroom, shower room, and utility room, as well as an exhaust fan with timer (115 cubic meters) in the kitchen. In the kitchen, we will integrate a recirculating hood that filters grease and odors. This will be linked with the exhaust fan, meaning the fan starts when the recirculating hood is turned on and stops later via the timer (we still need to test whether 5, 10, or 15 minutes works best).
In the living room, office, bedroom, and children’s rooms, there will be decentralized fans with heat recovery (switchable per floor). The fans have an air circulation volume of 27 cubic meters on level 2, which provides comfortable ventilation. They can also be adjusted down to 50% or increased for rapid ventilation as needed (or turned off completely). The heat recovery ensures that fresh air is preheated in winter. If desired, a timer can be added to turn off ventilation during, for example, the falling asleep phase.
This is how we will proceed. Our questions and concerns were addressed at the ventilation office. If you want, I can send you more information via private message.
N
nordanney29 Nov 2013 13:06The concept of f-pNo sounds coherent. However, is the entire system significantly cheaper than mechanical ventilation with heat recovery? Unfortunately, I have no experience with it, as we chose the central mechanical ventilation with heat recovery right away.
nordanney schrieb:
f-pNo’s concept sounds coherent. But is the entire system significantly cheaper than a mechanical ventilation system with heat recovery? Unfortunately, I have no experience with this, as we opted directly for a central mechanical ventilation system with heat recovery.Thank you – costs are in the private message – I would appreciate some feedback.
N
nordanney29 Nov 2013 13:52f-pNo schrieb:
Thanks – see the cost in the private message – I would appreciate your feedback. Already done! Thanks!
A well-planned central mechanical ventilation system with heat recovery no longer costs more than 10,000 (ten thousand), that’s a thing of the past... at least if you have a fair ventilation installer.
It is still unfortunate that controlled mechanical ventilation systems are often rejected in new builds... and installing decentralized systems in new buildings is almost just as bad...
But well, at least some form of ventilation is better than nothing—better a crutch than nothing at all...
It is still unfortunate that controlled mechanical ventilation systems are often rejected in new builds... and installing decentralized systems in new buildings is almost just as bad...
But well, at least some form of ventilation is better than nothing—better a crutch than nothing at all...
Hi f-pNo,
finally, someone who questions this controlled mechanical ventilation madness!
Regarding problem 1:
The trick is not to measure and control the humidity in the wet rooms, but rather in the living areas. This is ensured, for example, with humidity-controlled air vents from aereco. These devices regulate the humidity in the living spaces. The humidity in the wet rooms is not critical since the exhaust fans run for a while after the light is turned off (e.g., 5 minutes), or the exhaust fan is always running in those rooms anyway.
Regarding problem 2:
Yes, fresh air always comes in. The humidity-controlled air vents have a minimum airflow rate, meaning they never fully close automatically. If you want to close them completely, you can do so manually, for example, in case of outdoor odors. Also, the exhaust fan never completely shuts off. So, there is always sufficient air exchange.
Regarding problem 3:
In winter, the humidity-controlled air vents are usually not very open due to the generally low humidity. The problem is small, but it exists. I will send you experience reports via PM. Unfortunately, linking is not allowed in this strange forum. From an economic point of view, this cold air does not play a very big role — about 50-70 EUR more heating costs per year compared to 150 EUR for electricity and filter costs for the controlled mechanical ventilation.
Regarding problem 4:
No idea.
We also choose to forgo this controlled mechanical ventilation. It is way too expensive, and you can achieve good living quality without it. The energy-saving regulations are not a problem. According to the energy calculation, we will have a KfW20 house, heated with a gas condensing boiler, which saves us from that super-expensive heat pump stuff.
finally, someone who questions this controlled mechanical ventilation madness!
Regarding problem 1:
The trick is not to measure and control the humidity in the wet rooms, but rather in the living areas. This is ensured, for example, with humidity-controlled air vents from aereco. These devices regulate the humidity in the living spaces. The humidity in the wet rooms is not critical since the exhaust fans run for a while after the light is turned off (e.g., 5 minutes), or the exhaust fan is always running in those rooms anyway.
Regarding problem 2:
Yes, fresh air always comes in. The humidity-controlled air vents have a minimum airflow rate, meaning they never fully close automatically. If you want to close them completely, you can do so manually, for example, in case of outdoor odors. Also, the exhaust fan never completely shuts off. So, there is always sufficient air exchange.
Regarding problem 3:
In winter, the humidity-controlled air vents are usually not very open due to the generally low humidity. The problem is small, but it exists. I will send you experience reports via PM. Unfortunately, linking is not allowed in this strange forum. From an economic point of view, this cold air does not play a very big role — about 50-70 EUR more heating costs per year compared to 150 EUR for electricity and filter costs for the controlled mechanical ventilation.
Regarding problem 4:
No idea.
We also choose to forgo this controlled mechanical ventilation. It is way too expensive, and you can achieve good living quality without it. The energy-saving regulations are not a problem. According to the energy calculation, we will have a KfW20 house, heated with a gas condensing boiler, which saves us from that super-expensive heat pump stuff.
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