En suite extractor fan

[colorado]

Planning a refurb of an en suite and one of the issues is mould around the shower and on the ceiling.
Room is 1.75m wide x 3.3m long x 2.35 high. Along the long wall the ceiling slopes for about half the width of the room taking the height down to 1.8m. No windows.
Currently have a Marley fan through the wall above the toilet to 100mm rigid duct down through eaves to soffit, distance around 3m.
I was thinking of an inline fan above the ceiling to improve the extraction, so my questions are:
1. I would need to use rectangular duct to get down between the sloping ceiling and the roof. Should I go circular from grille to fan, then fan to converter to rectangular, then should I go back to round profile through the eaves, or just continue rectangular duct down to the soffit.
2. Should I position the extract grille above the shower where the moisture is, or in the middle of the room, or at the toilet end of the room to create a flow through the room.
3. Current fan is triggered from the light switch with an overrun timer. I would want to continue with this arrangement. Should I still install a 3 pole isolator switch?
4. Any recommendations on choice of in line fan. Lots of them look very similar but are there features worth looking out for?

 

[ericmark]

For a fan to extract air, the air also needs to enter the room, a grille in the door or wall to let air in will likely work better than an extra fan.

 

[colorado]

Thanks, I hadn’t thought of that.

 

[SUNRAY]

For a fan to extract air, the air also needs to enter the room, a grille in the door View attachment 266163 or wall to let air in will likely work better than an extra fan.

It's a shame builders don't understand this simple fact. Looking in a new build recently I shut the door to the 'cloakroom' and immediately the fan laboured. I mentioned it to the sales woman and she said they're all like it.

 

[SUNRAY]

Been talking over dinner about this, my friend reckons the couldn't pull the cloakroom door closed to latch from the outside with the fan running. But they could do it by pushing from inside.

 

[JohnD]

4. Any recommendations on choice of in line fan. Lots of them look very similar but are there features worth looking out for?

IMO the Soler & Palau "silent" fans are the best I have seen. Some are marketed under the "Envirovent" brand which is the UK subsidiary.

The inline fans can be quieter and more powerful than a simple wall- or ceiling-mounted fan, ideally fitted in the loft and mounted on a thick ply board, screwed to the joists or rafter but isolated with a pad of carpet underlay or similar.

Rigid duct is better than flexible. Ideally have it sloping down to the outside so any condensation drips out; otherwise, get the insulated duct.

The power required depends on the size of the room and how often you have steamy showers. Your old fan might be a typical "builder's" fan with a nominal flow around 80cu.m/hr which is not enough.

I strongly recommend a fan that comes on with the lightswitch, and has a timed run-on. If you are anxious about night time noise, try to experience an S&P Silent. It is not noisy like old or cheap fans.

Water vapour is lighter than air so will naturally rise towards the ceiling, so ceiling mounted fan or grille position is less critical. Wall extractors are preferably fitted opposite the point of air entry (usually the door) so there is a direct airflow with no dead air.

 

[JohnD]

It's a shame builders don't understand this simple fact. Looking in a new build recently I shut the door to the 'cloakroom' and immediately the fan laboured. I mentioned it to the sales woman and she said they're all like it.

I've had good results with a simple small gap under the door.

 

[SUNRAY]

I've had good results with a simple small gap under the door.

Indeed yes, however a 'drafty' door is considered wrong by a carpenter and liable to be draftproofed later.

 

[colorado]

Thanks John that looks ideal for less than £100.
The converter seems to go from 100mm round to 110x 54 rectangular which is a smaller cross section. Will this affect noise or performance?

 

[JohnD]

Restricting the size will make it a bit noisier.

Isn't there a bigger one?

 

[colorado]

Ah, found I can get 100mm round to rectangular 204 x 60mm which would still fit between the rafters.