Bathroom loft extractor fan

20 May 2013
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United Kingdom
Hi All,

Am planning the bathroom in a loft conversion. No insulation in yet so have full acces to the rafters. Would like to put an extractor fan above the shower which will be furthest from the window and on the opposite side of the wall from the door. I would duct it the eave/fascia area.

The insulation will leave a minimum vertical gap of 60mm. Is it possible to get slim ducting that would fit this gap and if so would it be detrimental to the required 50mm air gap? It's a flat roof dormer where the bathroom is situated.

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Would this be any good? It was designed for cooker hoods, so the duct could lie flat on the top of kitchen cupboards and be out of sight. Best used with a centrifugal fan as these generate more pressure than axial fans, which will help overcome the increased air resistance in this type of duct.

Rectangular to circular adapters are available for the ends.
Thanks for that. Might be struggling to find a fan that will fit in the void but will keep that section in mind.

Anyone know if shoving this in the 50mm air gap is against building regs?
Have though of an alternative to putting the duct in the void. As much as I don't like boxing things in I could probably make this look like a shelf for TP etc. I have shown the fan unit about 400mm (shown in the green box) from the shower recess but this could go closer to the outside wall (shown with window cutout).

Anything I've missed with a suitably IP rated fan placed like this?

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Looks good to me. A slight slope downwards to the outlet will make sure that if any condensation forms inside the duct that it will run outside. You will need to make provision for access to the fan for maintenance, or use a suitably IP rated wall mounted one in the shower.

I did something similar a few years a go for a mate where a duct ran through his lounge. I extended the 'boxing' by a few inches and incorporated some LED down-lights in the bottom illuminating pictures below, to make it a feature. The fan was wall mounted in the bathroom, so only the duct went through the boxing meaning there was no requirement for access.

I was quite proud of my sketch, until I saw yours :cry:
Thanks for that, good idea on fall of vent. Also like the lights idea but will refrain from highlighting the toilet in this instance :)

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