DIY Doctor UK DIY Forums

Hi all
Would appreciate some advice please for fitting an extractor fan in the bathroom. I'd like to do this myself to save costs and then have an electrician in to do the wiring.

I plan to fit it to the ceiling, and run the ducting through the loft to an existing hole through the wall which is around 5' above the loft floor. Not sure what size/power fan I need, bathroom is around 7' x 7' and total duct length would be around 7'
Also, what type of ducting best to use - flexible or solid? upvc or aluminium? Flexible is easier, i guess, but how to insulate it when most of it will run vertically? Do i still need to insulate if I use rigid plastic?

And if i get a fan with a backdraft shutter do i also need a non-return valve on the external cover? If so, would i need a more powerful fan?



Thanks in advance for any advice you can give me.

Michelle

Hi michc,
I'd recommend you fit an in-line centrifugal fan kit, this will have a better extraction rate than an axial fan and will be quieter. All electrics will be outside the bathroom, the extraction vent can be directly over the shower area, with dips in the ducting either side of the fan you should not need to worry about condensation.
Regards S

Thanks Stoneyboy, i'll have a look at that. Not sure how dips in the ducting would stop condensation though. Wouldn't it just sit in the pipe and build up?

Hi michc,
Condensation will not be forming all the time, it will only happen when extracting damp air and the loft temperatures are low enough. If the fan was continuously running and the bathroom in continuous use then yes there may be a problem with condensate accumulation.
Try the centrifugal fan with dips in the ducting and address condensate problems if these occur.
Regards S

OK. Condensation/damp is an ongoing problem in this house, so I'm probably worrying too much about it and anticipating problems before they happen.

Thanks again for your help

Mich