Hi All - wondering if anyone can advise on the following

My bathroom isn't very well ventilated and potentially this could become a problem (I mean condensation, before anyone says 'light a candle' ). We live in a terraced house with the bathroom directly beneath the apex of the roof, so there's no bathroom window (and I presume next door won't let me install a wall vent either ). The legacy system consists of an axial fan in the bathroom ceiling with 100mm ducting running ~3m vertically through a vent in the apex of the roof, it doesn't really cut the mustard as I'm unable to discern any movement of air at all at the fan end (it does get dusty though so it must be doing something).

Now I've read about on the net and there seems to be a right art to ventilating a bathroom :confused: . Basically I can either keep the ducting going up to the roof OR run a duct about 3.5m metres (plus some for the elbows) horizontally through the loft to the eaves. Either way, I think a meatier centrifugal-type fan is called for - am I right? What would be better, an in-line one located in the loft or one like this:

http://www.alertelectrical.com/product.asp?typeID=113&subID=181&prodID=2410

(I actually quite fancy a bad mother like this http://www.alertelectrical.com/product.asp?typeID=113&subID=176&prodID=2327 YEAH BABY :yeahdude: - it's a bit more expensive though)

I understand centrifugal fans are noisier but if I put an in-line one in the loft surely it would be quieter than an axial fan on the bathroom ceiling?

Any pointers would be much appreciated

I would go for the bad mother. We put one of these in to a large house to do exactly the job you want except we were extracting from a ground floor toilet up and through the roof.

What dimensions are your bathroom HxDxW. I'll get someone in the office to calculate the fan size you need based on the air changes required for an internal bathroom.

That's very kind of you

My bathroom HxDxW in metres is 2.3 x 2.5 x 1.5. Having measured it, it's tiny!

But still I quite fancy the big in-duct fan as then I could have a nice flat vent on the ceiling - the centrifugal fans that go on the ceiling seem to be quite bulky (though it would be out of the way).

What sort of minimum litres/second or cubic metres per second should I consider then? (I'll keep the ducting in the loft vertical, so will be 100mm ducting rising just over 3 metres vertically through an unheated loft, with a reasonably restrictive roof-tile-grille at the top)