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

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