Length of extractor fan ducting

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Is there a limit to when an extractor fan becomes useless due to the length of ducting it has to expel air through? I have a WC in the corner of a GF middle room, the most convenient route is straight up within the soil casing and out the roof, but it's 3 stories high - approx 12m to the roof line. Is it pointless fitting one?
 
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Condensation will be your greatest enemy, particularly when temp's are low.

A decent fan will still push air out resulting in a fair exchange of air to the room in question. Only trouble is is how you deal with the condensation that will inevitably build up in the pipe and ultimately drip down.

Condensation trap?
 
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All extractor fans are rated for maximum duct length. If you know the length of the duct go to one of the manufacturers websites and select a fan that will suit.
 
Only trouble is is how you deal with the condensation that will inevitably build up in the pipe and ultimately drip down.

It's just for a loo and sink - there won't be any condensation from that will there?
 
It's just for a loo and sink - there won't be any condensation from that will there?

That part of the duct that passes through your roof space is the main problem bit.

Air in your house will be warm and moisture laden. When in contact with a cold surface, condensation may occur. So the bit of duct in the roof space will be cold in winter and there would be risk of condensation. Insulation around that bit of duct would reduce the risk.
 

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