geraldthehamster wrote:
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

I've recently fitted a bathroom fan that vented to the eaves space. I
found two problems:

1. The fan was not powerful enough to open the one way valve flap thing
that I stuck inside the duct. Major drag as I had to dismantle it all
and take it out. This means drafts can now blow down the duct and heat
can drift out of the bathroom into the eaves space. In principle you
could use such valve flap things (I don't know what they are called) to
allow you to connect two ducts into one - they should stop blow back
down the other duct - provided your fan is powerful enough to open the
valve!

2. Condensation was a major problem. The day after fitting the duct and
fan the following morning the floor was wet under the fan and water
droplets hanging off the fan. Not good. I wrapped insulation material
around the duct in the attic space and this has eliminated the
condensation problem.

Hope this helps. Anyone else have problems with fans not being strong
enough to open the one way flap valves?


--
David in Normandy.
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