Do you recognize the following problem? Despite the fact that there is a bathroom fan, the bathroom still feels damp. Why?
Whether a bathroom fan will be effective depends on several factors. The fan must be able to move a sufficient flow rate, and must also be able to overcome the back pressure of the exhaust duct and the outer wall grille.
But there is so much more to consider:
What is often overlooked is that the efficiency of a fan does not only depend on what can be found downstream (the flexible duct, the outer wall grille, possibly a backdraft valve), but also on what happens at the front of the fan: the air supply to the room is just as important as the air exhaust. In other words, what can't go in, can't get out. In recent buildings, it has been taken into account that the door of a bathroom does not fit too closely to the floor. Often there is a gap of about half a centimeter to be found. This ensures guarantees incoming air in the bathroom, so that the bathroom fan can discharge the moist air without too much resistance. In older houses, however, this extra gap is not existing. A door grille can offer a solution here. If the customer is not in favor of this, there is no other option than to leave the door or window ajar in order to literally give the fan more breathing room.
