Bathroom extractor fan

robj20 · 7 Jul 2020 at 15:16

Going to be fitting a new shower very soon (Mira Platinum) and want to fit a new extractor fan. We have one of those useless through the wall things.
I want to change it for an inline one in the loft, what i want to know is genuinely what size is good to keep the room clear.
Bathroom is 1.9M x 1.7M and 2.4M high. The guidlines say what we have is sufficient but everyone knows they're rubbish.
So at the minute i'm thinking the Manrose MF100 (180-245m3/h) should be enough or should i fit the MF125 (240-310m3/h).

a1ex2001 · 7 Jul 2020 at 16:00

robj20 said:
Going to be fitting a new shower very soon (Mira Platinum) and want to fit a new extractor fan. We have one of those useless through the wall things.
I want to change it for an inline one in the loft, what i want to know is genuinely what size is good to keep the room clear.
Bathroom is 1.9M x 1.7M and 2.4M high. The guidlines say what we have is sufficient but everyone knows they're rubbish.
So at the minute i'm thinking the Manrose MF100 (180-245m3/h) should be enough or should i fit the MF125 (240-310m3/h).

We have the mf100 in a bigger bathroom and it does a great job, the vent is right above the shower, it still gets abit steamy on a cold morning but by the time you've finished drying the room is clear and you can see yourself in the mirror which is a massive change from the old in wall fan which left the place running with water on a winters morning.

200sols · 7 Jul 2020 at 16:01

You have 4" duct and outlet so stick with the 4" fan. The MF100 is more than capable.

robj20 · 7 Jul 2020 at 16:05

a1ex2001 said:
We have the mf100 in a bigger bathroom and it does a great job, the vent is right above the shower, it still gets abit steamy on a cold morning but by the time you've finished drying the room is clear and you can see yourself in the mirror which is a massive change from the old in wall fan which left the place running with water on a winters morning.

Great thanks, added bonus that my drill is okay to do the required 117mm hole.

a1ex2001 · 7 Jul 2020 at 20:08

robj20 said:
Great thanks, added bonus that my drill is okay to do the required 117mm hole.

Ours goes out of a roof vent was very impressed when we got it!

robj20 · 7 Jul 2020 at 20:54

200sols said:
You have 4" duct and outlet so stick with the 4" fan. The MF100 is more than capable.

I don't have any duct or outlet yet.

Mysterae_ · 7 Jul 2020 at 21:12

This is a job I'm about to do myself.

A tip I was given was to use new soil pipe where possible, for example between the shower room and fan and again between the fan and exterior vent. This is to prevent fluff and moisture being caught in the corrugated flexible ducting that you'd normally use. When the steam/water vapour enters the loft it can condensate back in to water and get trapped in the grooves of the corrugated ducting, where it'll eventually rot over the years. Using soil pipe means you can give it a bit of a gradient so it goes outside - if it moisture was ever trapped at all.

Slade2 · 7 Jul 2020 at 21:13

I need to do this for our shower as well we currently have no active ventilation apart from leaving the door open and the window after a shower, not ideal in the winter of course.

The main question I have is how are you going to exhaust the moist air? I have looked at this a few times and the response most of the time is loft and then out the gable wall through a 4inch hole? I did read you can also vent through the soft fit but I also read that can cause damp issues with the wind blowing the moist air back into the loft space.

I can get into the loft and drill to the outside but currently I dont have a ladder long enough to get high enough on the outside, to fit a cover or anything and I suppose drilling in is better than drilling out?

JRJ · 7 Jul 2020 at 21:24

Mysterae_ said:
This is a job I'm about to do myself.

A tip I was given was to use new soil pipe where possible, for example between the shower room and fan and again between the fan and exterior vent. This is to prevent fluff and moisture being caught in the corrugated flexible ducting that you'd normally use. When the steam/water vapour enters the loft it can condensate back in to water and get trapped in the grooves of the corrugated ducting, where it'll eventually rot over the years. Using soil pipe means you can give it a bit of a gradient so it goes outside - if it moisture was ever trapped at all.

Just to add to this, building inspector on our renovation wants solid ducting to avoid condensation and sagging of corrugated pipe, makes perfect sense and its cheap.

robj20 · 7 Jul 2020 at 22:28

Yeah I won't be using flexible. Solid ducting only and as short as possible.

InQ · 7 Jul 2020 at 22:54

Had a Vent Axia in line fan fitted 18 months ago and its made a slight difference but the room still gets steamy/damp tiled walls. I think the issue is we have a P shape bath with shower and there is the curved screen but no screen between the wall and the curved screen so the steam is able to blast off into the room easily.
Do all your setups just have a shower cubicle or enclosed shower area otherwise?

robj20 · 8 Jul 2020 at 15:53

I want a switch to control the fan, but hate those pull cord options.
Ideally would like something bathroom safe, i liked the look of this but you wouldnt know if it was on or off.
https://smile.amazon.co.uk/gp/produ...&pf_rd_p=e632fea2-678f-4848-9a97-bcecda59cb4e

But you get the idea, i dont like PIR or humidity sensors.

b0rn2sk8 · 9 Jul 2020 at 00:57

Can you excuse via a soffit? It’s the easiest place to install the excuse vent.

robj20 · 9 Jul 2020 at 05:24

b0rn2sk8 said:
Can you excuse via a soffit? It’s the easiest place to install the excuse vent.

Not an option. Drilling isn't a problem.

j.col · 9 Jul 2020 at 12:38

A very good inline fan is a rvk 100. 184m3/h

They seem very popular with the hydroponics crowd

Or they do a 125mm version 220m3/h and you can also buy a 5" to 4" reducer