Condensation from extractor fan

16 Jan 2007
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United Kingdom
I noticed a pool of water on the ensuite floor this morning and on closer inspection it is coming from the ceiling mounted extractor fan. Initially I thought it must be a burst pipe but it is actually condensation dripping down the duct from the inside of the roof vent.

There is a radiator more or less beneath the fan so the heat must be rising through the fan in to the duct and then condensing. I haven't noticed this before as I don't normally have the heating on upstairs but did yesterday. Is there any way of preventing this? The extractor fan has self-closing fins which should prevent much of the rising heat getting in to the duct.
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We must be at cross purposes. The duct is vertical link between the roof vent and the extractor fan.
Vertical link eh? Does the damp inside coincide with rain outside?
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i had this issue last year.... the duct in the loft had a dip in it which allowed the condense to collect and run back into the bathroom. it was simply fixed with a few clips to allow a constant rise.
you can prevent condensation ocurring in the duct by wrapping it in insulation, so it does not chill the warm damp air. A horizontal duct is easy, a vertical one you will need to tie or tape it on. I would go for either the stuff in a plastic sleeve, or the white fibre loft insulation recently introduced, which is not glass fibre but recycled from plastic bottles. It makes no irritant dust or itchy fibres and is very clean and pleasant to use.

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