Bathroom fan hardly reduces the high humidity

I have an AIRFLOW ICON 15 fan in the ceiling of our bathroom. With 1.5 meters of flexible ducting in the loft to an outside wall. The bathroom is 203cm by 166cm and height 203cm.

The fan clears the steam very quickly but takes ages to reduce the humidity.

Before using the shower my Hygrometer showed a humidity reading of 51% and after a shower the humidity reaches 90%.

With the fan running for a couple of hours the humidity only drops to 81%.

Prior to having the fan installed the tiled walls were so wet and I had hoped that the fan would reduce the humidity quicker than this.

Am I being too optimistic ?

Should I get a different fan ?

I asked AIRFLOW but they said every bathroom is different and couldn't give any suggestions.

Have you tried opening the window?

The fan you mention is low power and insufficient for a steamy shower. The flexible duct will reduce it still more.

You can get a ducted inline fan with three times the power and put it in the loft.

You mention wet walls. Are these external walls, uninsulated and cold? How do you heat the room?

This is a cheap one
https://www.tlc-direct.co.uk/Products/MRCFD200T.html

This is a good one
https://www.tlc-direct.co.uk/Products/SLTD250T.html

If you are able to fit rigid duct it will stay cleaner, give better airflow, and you can tilt it so any condensation runs outside.

You have explained air out, how does air get back in? Is there a vent in the bathroom door, or is the door left open?

Also it is relative humidity, the relative bit means temperature matters. So draw air from cold outside to replace air blown out and because it cools the room it will seem high humidity, but once air has warmed again it will show as low humidity.

I have noticed a huge difference with new house in time to dry cloths, because we now have a utility room, unheated with tumble drier in, when it runs window is opened so drawing cold air from outside which since cold holds less moisture, so cloths dry faster.

winston1 said:

Have you tried opening the window?

Click to expand...

Yes

JohnD said:

The fan you mention is low power and insufficient for a steamy shower. The flexible duct will reduce it still more.

You can get a ducted inline fan with three times the power and put it in the loft.

You mention wet walls. Are these external walls, uninsulated and cold? How do you heat the room?

This is a cheap one
https://www.tlc-direct.co.uk/Products/MRCFD200T.html

This is a good one
https://www.tlc-direct.co.uk/Products/SLTD250T.html

If you are able to fit rigid duct it will stay cleaner, give better airflow, and you can tilt it so any condensation runs outside.

Click to expand...

Thanks John. I half expected it is too low power. It was chosen by a bathroom installer who did not tell me anything about the fan, mistakenly I accepted his choice without checking !

ericmark said:

You have explained air out, how does air get back in? Is there a vent in the bathroom door, or is the door left open?

Also it is relative humidity, the relative bit means temperature matters. So draw air from cold outside to replace air blown out and because it cools the room it will seem high humidity, but once air has warmed again it will show as low humidity.

I have noticed a huge difference with new house in time to dry cloths, because we now have a utility room, unheated with tumble drier in, when it runs window is opened so drawing cold air from outside which since cold holds less moisture, so cloths dry faster.

Click to expand...

Ericmark, yes the door is left open and the wall next to the bath/shower is a tiled north facing wall so that probably doesn't help. I bought a dehumidifier which I leave just outside the bathroom (with the door open) and it draws the moisture out quite well.

I had in last 5 years three houses I have lived in, only one had a problem, and I started scratching my head to work out why one was getting mould growth and other two had no problem, and I concluded it was down to the doors on the shower, mother's old house was a wet room, no shower curtains, has extractor but never used, this house the door to shower seals at bottom, house with problem shower was in the bath, and that was it seems main problem, there was a gap bottom and top and we got the chimney effect, the moisture was circulating from shower into rest of bath room, so after a shower whole room damp, not just cubical and there was simply too much to dry out.

Other two houses the moisture was not circulated, it went were it should go, down the drain. The shower cubical needs to seal either at top or bottom so damp air not circulated. The massive hole below the shower doors when fitted to a bath resulted in the moisture getting into the whole room.

I also noted this house bedrooms etc 58% humidity, the home with problem was more like 75% humidity, never worked out why, father-in-laws house same design two doors up even worse, 80-85% humidity which we blamed on gas cooking.

Think main reason this house low, is size of house, three floors. And only two of us.

In my house, CWI made the biggest difference. The walls were warmer so stopped getting condensation in winter.

Also have a modern quiet fan that comes on with the light switch.

Do you have an adequate air supply into the bathroom to replace the air you're sucking ?