On 17 Nov, 16:24, "BigWallop" wrote:
"geraldthehamster" wrote in message

...





Right, I'm going to make a cods of describing this, but here goes.

Two small bathrooms, one above the other, in a dormer bungalow under
redevelopment. Both need extractor fans (the lower one has a window
that was once external but now opens into an entrance hall).

The upper bathroom will have an extractor in the ceiling, which will
duct to a vent chimney thing that replaces one of the tiles in the
sloping roof above the ceiling.

It would be possible to extract the lower bathroom by means of a
ceiling fan that ducts up into the eaves space, then up inside the
sloping roof, joining the same vent chimney thing Above the upper
bathroom ceiling by means of some kind of T.

Is this a good idea, or might I end up blowing wet air from one
bathroom into the other, or causing water to condense and run down the
duct into the other bathroom? Would it be better simply to put in a
second vent chimney thing lower down, in the eaves, to vent the lower
bathroom independently?

Most importantly, has anyone here actually combined vents like this,
or seen it done? Is it an orthodox thing to do, or not?

Cheers
Richard

Right. *To start with, your duct pipes don't have to be round (circular).
Square or rectangular plastic duct can also be used, as long as it equals
roughly the same internal area as a 4 inch tube. *A 110 mm (4 inch) pipe has
a circumference of 345 *mm and internal area of almost 9.5 mtrs, so you need
a square duct of the same measurement to allow the same air flow through it.
A 50 mm X 195 mm rectangular duct has nearly the same area as the 110 mm
pipe, so allows the same air flow through it. *A 25 mm X 375 mm rectangular
duct also allows the same air flow through it.

Because the shape of the duct has changed, it can allow the venting system
to be hidden inside the dry lining or even in the wall cavity. *The shape
doesn't restrict the air flow through the vent, it just allows the ducting
system to be placed in areas where a round pipe would be ugly to look at, or
need lots of horrible boxing in.

So, now you know of an alternative to the vent pipe, do you see any other
way the duct could to be routed more conveniently if it was a different
shape? *There are adapters to suit almost all shapes and sizes of pipe, so
that's also not a worry.- Hide quoted text -

- Show quoted text -

Thanks - I know this already ;-) At least some of the ducting from the
ground floor bathroom will have to be rectangular, to get up between
the rafters from the eaves space, to meet up with the other ducting
and connect to the vent chimney. My question remains the same - is it
a good idea to have two vent ducts meeting like this and sharing the
same chimney? Or, am I likely to push wet air from one bathroom into
another, or to end up with condensing water running back down one of
the ducts?


Cheers
Richard