Fans

And a decentralized system also seems to be similarly costly due to the number of rooms and additionally causes quite a few holes in the beautiful facade...

Now the heating engineer, who also installs ventilation systems, suggested installing fans in the exterior walls for the wet rooms (guest WC and bathroom), which are controlled by push-button and/or humidity sensors and extract the humid air from the room.

Additionally, an exhaust hood is recommended in the kitchen.

Hi,

until last week we were also torn back and forth, but already tended towards a decentralized system. Our general contractor also planned exhaust fans in the wet rooms (bathroom, shower bathroom, kitchen, and utility room) as well as exterior wall air vents (ALD), which are intended to allow fresh air to flow in. Our uncertainty was very high.

Since it is now slowly moving towards signing and we finally wanted clarity, we were at a ventilation office near Berlin last week. Of course, the advisor there wanted to sell us something, but in my opinion the consultation was fine and shed some light on the matter.

The proposed concept: The exhaust fans draw moist air from the wet rooms (the smaller fans circulate 60 - 80 cubic meters of air per hour). They are controlled by a timer and possibly a humidity sensor. By extracting the exhaust air, a vacuum is created. This is balanced by fresh air being drawn in through the exterior wall air vents (ALD). So far, so good.

Problems: 1. The moisture is extracted from the wet rooms. Once the humidity sensor reports that the set limit has been undershot, it turns off the fan (possibly with a run-on period by the timer). Other humidity, such as the moisture that arises solely from people being in the house, is not extracted via this system (apart from the intermittent vacuum). That means, for example, at night when a person loses about 1 liter of fluid, it remains inside the house. 2. Fresh air only comes in when the exhaust fans are running. If they are off, you have little to no circulation. The "feel-good effect of fresh air" will hardly occur. You could possibly also set the exhaust fans to permanent operation—but then problem 3 comes into play. 3. The air drawn in through the ALDs is general outside air. In summer, therefore warm air, in winter pure cold air. On one hand, it can be quite unpleasant to sit in the cold draft; on the other, this air needs to be heated. If you want the "feel-good effect of fresh air" and switch the fans to permanent operation, you would constantly be pulling in ice-cold outdoor air in winter. 4. For allergy sufferers: exhaust fans pull air out. As far as I understand, pollen filters cannot be installed in the ALDs (but I'm not certain). That means pollen is also drawn into the house.

Exhaust hood: Here you have to be careful about how strong the exhaust hood is. There are hoods that draw up to 700 cubic meters of air per hour. This air must, of course, come from somewhere. So it is sucked in through the ALDs (which can whistle in the worst case :rolleyes: . (This is why Wastl asked about the chimney, because here, potentially, smoke no longer goes out the chimney but is pulled through the apartment into the kitchen—which does not apply to you.) You should therefore pay attention to how much air the exhaust hood extracts.

This is a layperson's opinion. Maybe the consultant was just very well trained (sales-wise). But he took away our uncertainty so that now we know what we will do. Others may see it differently.

We will: take exhaust fans with timer and moisture meter (60 - 80 cubic meters) in bathroom, shower bathroom, and utility room as well as an exhaust fan with timer (115 cubic meters) in the kitchen. In the kitchen, we will integrate a recirculation hood which filters out grease and odors. This will be operated together with the exhaust fan, i.e., the exhaust fan starts when the recirculation hood is turned on and ends later by timer (we need to test if 5, 10, or 15 minutes).

In the living room, office, bedroom, and children’s rooms we will install decentralized fans with heat recovery (controllable per floor). The fans have a circulation volume of 27 cubic meters at level 2, which provides pleasant ventilation. If needed, they can be turned down to 50% or increased for boost ventilation (of course, they can also be completely switched off). The heat recovery ensures that in winter, the fresh air flows in preheated. If necessary, a timer can be added, which, for example, turns off the ventilation during the falling asleep phase.

This is how we will do it. Our questions and reservations were cleared up at the ventilation office. If needed, I can send you info about this via PM.

The concept of f-pNo reads coherent. But is the entire construct significantly cheaper than the Controlled Residential Ventilation? Unfortunately, I have no experience with that, as we chose the central Controlled Residential Ventilation+Heat Recovery directly.

The concept of f-pNo sounds coherent. But is the entire system significantly cheaper than the Controlled Residential Ventilation? Unfortunately, I have no experience with that since we directly chose the central Controlled Residential Ventilation+Heat Recovery.

Thank you - costs see PM - I would appreciate feedback.

Thank you - costs see PM - I would appreciate a response.

Already done! Thanks!

A well-planned central controlled ventilation system no longer costs 10 thousand, that was once... at least if you have a fair ventilation installer...

It is sad that controlled ventilation systems are still often rejected in new buildings... and the installation of decentralized systems in a new building is almost just as bad...

But well, at least some kind of ventilation is better than nothing...

Hi f-pNo,

finally someone who questions this controlled residential ventilation madness!

Regarding problem 1: The trick is not to measure and regulate the humidity in the wet rooms, but in the living areas. This is ensured, for example, by the humidity-controlled ALDs from aereco. These things regulate so that the humidity in the living areas is right. The humidity in the wet rooms is uncritical because the fans run on (e.g., 5 minutes after the light is turned off) or the exhaust fan always runs in the rooms anyway.

Regarding problem 2: Yes, fresh air always comes in. Both the humidity-controlled ALDs have a minimum throughput, i.e., they never close completely automatically. If you still want to do that, of course, it can be done manually, e.g., in case of odor from outside. The exhaust fan never goes completely off either. So there is always sufficient air exchange.

Regarding problem 3: In winter, the humidity-controlled ALDs are usually not opened wide because of the rather low humidity. The problem is small but present. I will send you experience reports via PM about this. In this weird forum, one is not allowed to link. Economically, this cold air does not play a very big role. About 50-70 EUR more heating costs per year compared to 150 EUR electricity and filter costs for the controlled residential ventilation.

Regarding problem 4: no idea.

We also do without this controlled residential ventilation. Much too expensive and you can achieve living quality without it anyway. Energy saving regulation is not a problem. According to the energy calculation, we will have a KfW20 house. Heated with gas condensing technology, which saves us this hyper-expensive heat pump stuff.