Is this length of vent ducting feasible?

19 Nov 2010
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United Kingdom
I live in a grade II listed building and have been granted permission to covert a small bedromm in the front of the house to a shower room. In applying for the listing I neglected to specify an extractor outlet. I would hate to go through the application process again to get permission to install a grating on the front of the house. It would probably not be granted. So the idea is as follows:

1. Fit an inline centrifugal fan couped to a ceiling vent above the shower.
2. Take the exhaust through about 10m of ducting to a Y piece to couple with the bathroom extractor exhaust.

Points to consider.

1. Ducting resistance. Would it be crazy to expect a useful flow through this distance? Should I fit a reducer to, say increase the X sectional area to twice that of the 120mm outlet?
2. Condensation. I would need to duct vertically for about 1.5m above the fan outlet and then elbow to run on what I would hope would be a gradual fall to the Y piece Am I likely to avoid the condensation problem by wrapping and tapping a good thickness of roofing insulation around the duct for its whole length?

I have no experience of fitting extractors so I will be grateful for any advice.

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An industrial/ AC inline fan would be fine, get one with speed control. Look at hydroponics shops as they are used alot by growers.
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