Bathroom extrator, inlet required?

[dishman]

Does an extractor fan, to work efficiently, require an equal sized vent to pull air into the room?

Or is a gap under the door enough?

If a door gap is enough, what if the door is near the extractor, and not near the area where moisture is produced. Does this mean the extractor will be pulling air from under the door while moisture in the room is not properly extracted?

Does this mean therefore that an inlet vent needs to be placed near the source of moisture so that airflow will travel across the room pulling moisture into the extractor vent.

Recently started to have issues in a windowless bathroom. Trying to problem solve.

Extractor is old, but works fine, however I am replacing it with a modern model with better specs.

 

[JohnD]

water vapour is lighter rhan air, and naturally rises towards the ceiling. An extractor vent in or near the ceiling will draw it out.

fresh air entering under the door will naturally stratify under the warm damp air, provided it is not blown around and mixed togeter.

in this respect an extractor works better than an open window.

the suction created in the bathroom will also prevent water vapour diffusing through the home.

for peak efficiency, the extractor should be above the shower or bath, and the entry point of replecement air near the floor, oposite end to the extractor.

You say you have a windowless bathroom. If you have space above the ceiling or elsewhere, a modern inline ducted quiet fan with ball-bearing motor can have a nominal capacity around 240 cu.m/hr which should be sufficient.

 

[dishman]

Yeh, it's an odd one.

Either the tenant's habits changed or this centrifugal fan is just not pulling well any more.

It's a top floor flat, the extractor vents into a communal duct in a dry riser. So it is in a fixed position.

The bathroom is only 1.5m(w)x2.5m(l)x2m(h) and the shower and vent are on opposite sides of the room. with the door nearest the vent.

Never had issues in the bathroom before, so either the tenant's habits changed, the fan is not up to it, or the is not enough airflow. Lockdown could have made it worse....but it seems to have been an issue for more than the last year of her tenancy.

One possibility is that the tenant, for some reason, did say they started leaving the bathroom door open.

Perhaps vent was just sucking air in from the open door and the moist air was sticking in the bathroom. I have advised she keeps the door closed now.

I have also purchased a modern centrifugal fan. While the old one had great build quality, this one does move a larger volume of air, and is more aesthetically pleasing.

We shall see if it resolves the issue.

 

[vxxbcks]

The ducts also get restricted with dust over the years.