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Best extractor for internal bathroom approx. 24 foot from external wall??

Hi, I've moved into a ground floor flat with a bathroom at the back with no external walls - the extractor fan we now realise is only circulating air within a cavity between the ceiling and false ceiling that was installed. This is obviously totally ridiculous and the cavity (and possibly upstairs floor joists??) is containing all the condensation - damp and mouldy - yellow fungus has started creeping through the false ceiling into the room. We intend to take out the false ceiling, check the joists/floor above and install an extractor fan but the duct will have to either run through our bedroom to an external wall (rather not) or through the cellar, under our bedroom and out (if possible??) the cellar is very accessible and all pipework for our flat and some of that for flats above (eg. communal waste pipe) runs through the cellar so hoping there is some way to do this. Will we need a particularly powerful extractor for this distance? do we need a booster? Will we be able to run the duct from top of bathroom down and out or is this too inefficient?
Sorry for length of query, just going round in circles on-line… Any advice much appreciated!!

3 Answers from MyBuilder Electricians

Best Answer

you cannot go down as any moisture will collect at lowest point causing problems later on


Answered 23rd Sep 2015

Above 3 metres you must use a centrifugal fan as an axial is simply not powerful enough, the best I could find on the net was a ventaxia solo with some reports listing up-to a 50 metre ducting run as possible. Bear in mind for maximum performance the ducting needs to be as short and straight as possible, the ideal route would be through your bedroom and boxed in, best to use solid pipe and then packed in rockwool for sound deadening. Don't forget to glue and tape the joints.


Answered 12th Sep 2015

At 24ft, virtually all fans on the market will have poor performance. Ducting run needs to be as short as possible.


Answered 14th Sep 2015

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