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.
W
WilderSueden29 Mar 2023 22:47There are constant pressure changes of around 4%, which is why you were advised against it.
WilderSueden schrieb:
There are constant pressure changes of around 4%, which is why you were advised against it.If the basement room is completely airtight, then yes. If there is a gap under the interior door or if the door is opened, then not.
Besides that, why would such a pressure change be a problem?