If I want to ventilate a 25sqm (269 sqft) basement room with a high ventilation demand (due to high humidity) using two push-pull fans installed in the (small) basement window, which option is better:
(1) Two units side by side, operating in opposite directions, one pushing while the other pulls?
One always pushes, the other pulls. They switch every 70 seconds.
Pros
- The volume of air supplied always matches the volume extracted.
Cons
- There is a risk of a short circuit, meaning the supplied air is immediately drawn out again, while other parts of the room are ventilated and dehumidified much less effectively. Or is it sufficient that the two fans are directed in opposite directions?
(2) Two units side by side, operating in phase, both pushing or both pulling?
Both push for 70 seconds, then both pull for 70 seconds.
Pros
- Excess air in the room flows out through the room door into the rest of the house. When pulling air out, the loss is balanced by air flowing in from the house. Overall, an airflow should develop between the window and the room door, covering a large part of the room.
Cons
- A slight underpressure or overpressure builds up in the room because pushing and pulling do not occur simultaneously.
One detail worth mentioning: Outside, both fans vent into the same light well. Here, the risk of a short circuit (air blown out being drawn back in) could be even higher.
The Aereco representative said that option (2) is fine, while option (1) would not work at all. It is necessary to always work with a pair of fans so that air is simultaneously pushed and pulled.
A third solution would be a fan pair where one fan is installed in the problematic room and the other in an adjacent basement room.
(1) Two units side by side, operating in opposite directions, one pushing while the other pulls?
One always pushes, the other pulls. They switch every 70 seconds.
Pros
- The volume of air supplied always matches the volume extracted.
Cons
- There is a risk of a short circuit, meaning the supplied air is immediately drawn out again, while other parts of the room are ventilated and dehumidified much less effectively. Or is it sufficient that the two fans are directed in opposite directions?
(2) Two units side by side, operating in phase, both pushing or both pulling?
Both push for 70 seconds, then both pull for 70 seconds.
Pros
- Excess air in the room flows out through the room door into the rest of the house. When pulling air out, the loss is balanced by air flowing in from the house. Overall, an airflow should develop between the window and the room door, covering a large part of the room.
Cons
- A slight underpressure or overpressure builds up in the room because pushing and pulling do not occur simultaneously.
One detail worth mentioning: Outside, both fans vent into the same light well. Here, the risk of a short circuit (air blown out being drawn back in) could be even higher.
The Aereco representative said that option (2) is fine, while option (1) would not work at all. It is necessary to always work with a pair of fans so that air is simultaneously pushed and pulled.
A third solution would be a fan pair where one fan is installed in the problematic room and the other in an adjacent basement room.
R
RotorMotor29 Mar 2023 15:05Both solutions are not practical.
In option 1, the air is likely just being circulated without fresh exchange.
In option 2, you might draw moist, warm air from the living area into the basement, which can cause mold.
Why is this room so humid?
Is it possible to distribute the fans throughout the room?
In option 1, the air is likely just being circulated without fresh exchange.
In option 2, you might draw moist, warm air from the living area into the basement, which can cause mold.
Why is this room so humid?
Is it possible to distribute the fans throughout the room?
Here is an important detail: It is an almost KfW-55 standard house. The basement is heated. The whole house is fairly dry; during winter, we use humidifiers to raise the humidity from 30% to 55%.
Having two push-pull points in different locations would mean you can no longer use the window and light well but would have to drill through the wall and route the air upward outside in the ground. Alternatively, the air ducts could be led through the window, but both inside and outside they would need to be sufficiently spaced apart.
If option 2 is possible, that would be my preferred solution. I had been told that the system does not work unless the same amount of air is simultaneously exhausted and supplied. However, the differential pressure is not that high when air is only exhausted or supplied for about 70 seconds at a time.
Having two push-pull points in different locations would mean you can no longer use the window and light well but would have to drill through the wall and route the air upward outside in the ground. Alternatively, the air ducts could be led through the window, but both inside and outside they would need to be sufficiently spaced apart.
If option 2 is possible, that would be my preferred solution. I had been told that the system does not work unless the same amount of air is simultaneously exhausted and supplied. However, the differential pressure is not that high when air is only exhausted or supplied for about 70 seconds at a time.
R
RotorMotor29 Mar 2023 15:34Ah, then a few more questions: how accurate are the temperature and humidity measurements in each room?
W
WilderSueden29 Mar 2023 15:52Is this the pool room?
Roughly, I would estimate about 1 cubic meter per minute for these types of fans when running at full capacity. Let’s say your basement room has 65 cubic meters (2300 cubic feet), then pumping in 2 cubic meters (70 cubic feet) would be quite decent.
You should space them out a bit. Ours in the open area are on the same side but about 4 meters (13 feet) apart.
Roughly, I would estimate about 1 cubic meter per minute for these types of fans when running at full capacity. Let’s say your basement room has 65 cubic meters (2300 cubic feet), then pumping in 2 cubic meters (70 cubic feet) would be quite decent.
You should space them out a bit. Ours in the open area are on the same side but about 4 meters (13 feet) apart.
RotorMotor schrieb:
Ah, then a few more questions: how accurate are the temperature and humidity measurements in the respective rooms?WilderSueden schrieb:
Is that the pool room?
Roughly, I would estimate about 1 cubic meter per minute for such fans running at full capacity. Let’s say your basement room has 65 cubic meters, then supplying 2 cubic meters would be quite decent.
You should space them out a bit. Ours in the open-plan room are on the same side but about 4 meters (13 feet) apart.Thanks for the reply!
The room volume is 48 cubic meters (1,695 cubic feet).
What do you think about option 2)?
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