Bathroom extractor fan to roof tile vent

21 Oct 2014
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United Kingdom

Apologies if this has been covered elsewhere, but I can't seem to find the answer.

Our bathroom has no window, but an old inline fan in the loft which extracts from a vent in center of the room. The fan needs replacing as it's not powerful enough (and it sounds shot). It's just venting to 'near' the eaves. The roof design prevents the ducting from reaching the soffitt without hindrance, so that option is out.

- The extractor has a run on timer which is wired into the pull cord (light and fan come on at the same time)
- We have a roof tile vent to extract to (due to the soffitt problem)

My questions are as follows:

1. Venting to a roof tile means that the ducting will be going up and up, therefore there maybe a risk of condensation running back down the pipe.
- Would you always need a condensate trap for this? If so, where in the line of ducting do you put it?
- Where would the condensate go to?
- The distance from the current bathroom vent to the tile vent is approx 1.5 metres

2. I could move the vent in the bathroom over the shower (source of the moisture). This would mean that from there to the underside of the roof tile vent would be 0.5 metre in a straight line almost.
- Would there be any problems in having a short ducting bend (from bathroom vent) - inline fan - then short ducting to roof tile vent? Again what about condensation running straight back down - would this be a problem in such a short run?
- I would need to extend the cable that powers the fan also.

The roof tile vent has a duct opening of 110mm and most of the ducting is 100mm. are you supposed to use one of these:

Any ideas of the best option, course of action I should take, would be appreciated.

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Move the vent closer and run straightish up.

The only time I've ever seen condensation in such a situation proving a problem was when the installer had used a gurt long sagging run of 4" flexi and water had collected at the low point.

You could wrap loft insulation around the flexible duct and tie/gaffer tape it in place.
Cheers. That's what I was leaning too as it just made more sense.

Would there be a preference to use solid plastic ducting rather than flexi?

Last question, any recommendation for an inline fan for such a short run. Would need one with a run on timer, fairly quiet and the bathroom is fairly small.

Cheers again
I have one of these fitted.

Very quiet, shifts plenty of air. Adjustable run-on timer.

Just one thing......Make sure the circuitry is above, not below the fan.
Read the reviews, some users have had wet circuit boards due to condensation if fitted that way.


EDIT:- If you get one, the "bayonet" fixing for the inside bathroom grille is clockwise to undo. One or two may have been broken methinks.
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Hi Ian - just on this:

"Just one thing......Make sure the circuitry is above, not below the fan.
Read the reviews, some users have had wet circuit boards due to condensation if fitted that way."

The circuit board is set under the fan in a panel with two screws, with the fixing's for the joist under that. I figure you have to set the fan upside down, but then this makes it difficult to fix to a joist. Seems the fan is not actually fit for purpose.


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