Trying to extract 2.5 metres...

Afternoon, all - I'm writing to try and get some advice on ventilating a 10ft x 8ft downstairs bathroom if possible. I'd be grateful for any help, as I want to make sure it's fit for purpose!

Here goes... My downstairs bathroom is 'land-locked', with nearest route to an exterior wall about 9 feet away through the kitchen. Fortunately I have quite high ceilings (11ft or more, big, old Victorian house) so I can live with a pipe extracting close to the kitchen ceiling.

The extractor will be going horizontally from the bathroom, through the kitchen and to the outside.

As the distance the expelled air needs to travel is about 9ft, I could use some help, after having conflicting advice from different tradesfolk...

What sort of fan (inline, continuous, etc) should I go for, and what size?
What size/type of pipe or ducting should I use?
Do I need a special exterior vent? There is a louvred one on theoutside of the house already that I'm hoping to pick up and use, to save any more brickwork.

Currently there is a bath, sink and toilet in there, but I want to install an electric shower to the bath. I only recently moved in and there was a mustiness to the room. It didn't smell damp, but was a bit 'muggy', somehow. There are no leaks anywhere, and running water through the bath and sink traps helped, but I think it just needs better air flow.

I'm hoping that, as the extraction will be horizontal with no turns, it should be easy enough to do if I get the right gear.
Thanks in advance for any help!


  • Hi Could you confirm the ceiling height in the bathroom is also 11ft and could you confirm the size of the Louvre you're hoping to use

  • Hi again, apologies for being away for so long! The new roof is all done, at least...

    Yes, the bathroom height is also 11ft and the louvre I'm hoping to use is about 5" by 5", which covers a circular exit hold with an aperture of around 4 inches.

    Thanks for any help and advice!
    Kind regards,

  • Al
    That's quite a large bathroom and you need to decide if you want to meet building regulations, which states you need to move 54m3/hr or if you want the fan to actually clear the bathroom. If you go down the building regs route your 4" pipe is fine and you're looking to purchase any commercial standard 100mm mixed flow fan, such as a Manrose MF100T, as your Bathroom doesn't have any opening windows you need a timer model. If you want something to clear the room effectively your 4" pipe is too small and would need to be replaced with 8" pipe (200mm dia duct) or a rectangular duct size equivalent to 200mm dia, the same sized mixed flow fan such as a Manrose MF200T would be OK but most similar sized models would also be OK.
    From a design point of view the Building regs solution would need 54M3/hr at 10Pa
    For the effective solution you need 936m3/hr at 110Pa
    Any electrical wholesaler or HVAC distributor should be able to help.
    Please note the noise levels of any fans offered a 200mm dia fan is a lot noisier than a 100mm dia fan
    There is going to be a big difference between inlet noise - outlet noise and breakout noise make sure your aware of the inlet noise level (bathroom) and the outlet noise level (outside) as not all suppliers will publish this detail.
    If you want to pick some fans we can take a look if needed
    Please remember in most cases you do get what you pay for

  • A belated thank you for all of your help so far with this! Will bear in mind the noise level info too.
    Apologies for the delay in replying - other jobs have taken priority in a plenty-to-do house...

    Also, I'm a bit embarrassed that I supplied incorrect room measurements. The room actually measures 6' x 8' x 11'. I wondered, would I get away with a 6" mixed flow fan? (

    I've been looking at the Manrose and Vent-Axia mixed flow fans. Could you recommend a wall-mounted fan that could clear the room when the shower is being used but also provides a more economical, quieter constant trickle of air through when not at a high speed, please? (the bathroom is right beneath a bedroom so the quieter on trickle mode the better...) Some fans appear to have 'infinite speed control' but descriptions aren't that clear about how it's achieved, or whether the fan runs quieter when set on a low level.

    Then my plan is to find a pipe approx 2.5 metres long (avoiding joins) to extract through. I can use a straight pipe, as no bends are necessary, and hope to secure it to the wall or ceiling. What material pipe would you recommend and should I insulate it, do you think?

    Any advice is gratefully appreciated!
    I have an electrician friend coming in two days to replace two fans (u/s bathroom and kitchen) so I can pick his brains a bit as well.
    Thanks again,

  • Al
    Based on your info you now need around 150m/3hr of air at about 60Pa pressure loss. The best solution would be a Manrose 100T or vent Axia 100T they're both the same fans but with different branding (or something similar), run the fan at low speed and use semi rigid acoustic flex at 100mm dia (not insulated flex) mo t the fan as close to the middle as possible to allow for the same length of flex either side of the fan. I personally wouldn't worry about trickle, just for for a fan with a run on timer.
    For a wall mounted option, you'll need to go for a 150mm Wall fan something along the lines of a Vent Axia Silhouette 150T, anything that does 150m/hr will be OK but please watch for the noise levels as you know not all fans are built the same, again I wouldn't go for a trickle mode, just a timer. The wall mounted option is going to be quite noisy (around the noise level an electric kettle boiling would make) so the inline Option would be my preferred

  • Hi again, thanks for that

    There isn't room under the floorboards above so I'd hoped to set an inline fan 'into' the partition stud wall to then propel the air the 2.5 metres through the kitchen to the exterior wall. If I wanted the fan mid-way along the duct then I'd have to suspend it from the kitchen ceiling somehow.
    I haven't found any 'trickle' fans strong enough to do the extraction so will most likely go for a run-on timer as you suggest.
    I actually have a vent-axia silhouette for my u/s bathroom, which is much smaller and has a large openable window, but as the bathroom d/s has no window, I would rather get a more powerful fan like the inline to go the full 2.5 metres.
    I've just measured the partition wall from the d/s bath to the kitchen and it's only 90mm though, so I think I have some more research to do... If I were to house it there, it would need to be pretty slim.
    The previous owner's solution was to lower the ceiling and avoid using the room (!) but I'm sure it would be workable if I can find the right fan for the job.
    Thanks again for your help and info, it's all helping!
    Cheers, Al

  • no problem let us know if you need anything else

  • Hi again - I'm still trying to sort this bathroom fan...

    After a few electricians have gone 'off radar' regarding this job, the latest electrician to visit recommended a centrifugal fan to solve my situation (above). This would mean any noise generated remains in the bathroom (rather than having a ceiling-mounted in-line fan screwed to the kitchen ceiling). To this end, I have been looking for fans that are powerful enough to do the job while being installed in the bathroom (and not in the kitchen)

    I have found these fans:
    Solo Plus by Vent-Axia - Trickle: 32m3h, Min boost: 61m3h, Max boost: 80m3h

    Envirovent EFHT2S - Trickle: 54m3h, Min boost: 126m3h, Max boost: 216m3h

    iCON 60 - No trickle function, Max boost: 260m3h

    What do you think of these as a solution...? The literature for each fan claims that these fans can be ducted much further than the 2.5 metres required. (9 metres+)

    Admin, how did you come to the figure of 60Pa, please?
    Also, as the bathroom has no natural ventilation (t's windowless and 2.5 metres from outside wall), wouldn't a fan with a trickle option be advisable to maintain air flow and keep on top of the mustiness...?

    I know that an in-line fan would uaually be more powerful (tho some are weaker than the envirovent EFHT2S). However, I'm keen to contain the noise within the bathroom if I can.

    Any help would be greatly appreciated!
    Kind regards,

  • Al
    The Vent Axia fan won't give you the performance, so you can dismiss that one. The other 2 will give you the performance but at a cost of a high noise level with the Envirovent fan being the quietest at 36dB(A) at 3 metres compared to the Vent Axia ACM 100T on low speed at 16dB(A) at 3 metres.
    The best option if it can be incorporated is either the ACM 100T or manrose MF100T which are mixed flow fans and mount inline, this coupled with acoustic flex or insulated flex will give you the performance you need with the quietest noise level in the Bathroom and the Kitchen. I won't bore you with all the details but fan have 3 areas they create noise. The fan inlet the fan outlet and the fan breakout, the inline MF or ACM will be further silenced via the inlet and outlet with the flex which also minimizes the breakout. The 2 solutions you've suggested leave no way of reducing the noise on the inlet and unless you add acoustic or insulated flex to the outlet you'll experience breakout in the Kitchen.
    Ultimately the final choice is yours, we only offer advice. The 3 fans you've suggested are all designed to fit into bathrooms and are used everyday of the week, but we are here to offer you the best solution, so you have a system that's usable and a noise level that's acceptable.
    As discussed before, we would suggest just the run on timer facility should be OK if the Bathroom is heated, if the bathroom isn't heated a trickle solution would be a good idea, but no fan will be completely silent even in trickle mode and you may find you turn it off anyway.
    Hope of some help

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