Extractor fan size

[alphazulu]

I have an en-suite that is about 2 x 2 m and a sloping ceiling (the roof). It basically has two external walls, a wall to the bedroom and the fourth wall is a stud wall with a cupboard the other side. All the walls and sloping ceiling are tiled. There is a bath with a shower over it, just a mixer shower at mains pressure. Whenever we shower we get a lot of condensation forming on the walls and ceiling, even in summer. We already have an oversized radiator but no window. We have an inline fan (Manrose MF100T) which draws air from the wall next to the shower. There is about 1 m of ducting from the bathroom to the fan and then about another 3 m to where to duct exits the house. All the ducting is 4" insulated. This fan was an upgrade a couple of years ago but it did not solve the condensation problem. This fan has a max air flow of about 250 m3/h.

I have found a Vent Axia ACM150T for a good price so I'm thinking about installing this. This fan should be able to shift about 500 m3/h. This fan is a 6" model so I will need to replace the ducting and make a bigger hole in the wall. I don't want to go to all this effort if I won't see any improvement. Has anybody done this? Or have any idea whether this will improve things?

Would I see an improvement if I just connect it to the existing ducting? (changing the ducting to 6" when I get some spare time)

 

[flameport]

How does the air enter the room? Any extractor will be useless unless there is some way for an equivalent amount of air to enter the room, usually through a gap under the door.
The same applies to the rest of the building - making a property virtually air tight will make any extractor useless regardless of how powerful it is.

A 6 inch 500m3 fan for a 2x2m bathroom is grossly oversized.

 

[alphazulu]

There is about a 10 mm gap under the door. I'm just about to tile the floor so I'll make sure I keep that. It is an old house so we have plenty ventilation.

I thought a 6" fan would be too big but in a few places I have seen people say 4 or 5" are not enough for bathrooms without windows.

 

[endecotp]

That's not unlike my en-suite in terms of area and duct length. How long do you keep the fan on for after showering? Mine is normally on for a couple of hours or more.

 

[HERTS P&D]

20 minutes over run after the light has been turned off.

Andy

 

[alphazulu]

It has the max over run that the fan allows, about 15-20 mins. Usually the light is on for a while after showering. I connected up the 6" fan using the 4" ducting and it made a difference. Not as much steam the room and the mirror cleared faster. Now I just need to make the hole in the outside wall bigger and fit the new ducting.

 

[endecotp]

Increasing the time might be easier and just as effective as increasing the size of everything. Consider an external timer or possibly a humidistat.