Bathroom extraction
geraldthehamster
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
BigWallop
"geraldthehamster" <ric...@zulu.myzen.co.uk> wrote in message
news:eab701ed-baea-4913...@d10g2000pra.googlegroups.com...
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.
geraldthehamster
> "geraldthehamster" <rich...@zulu.myzen.co.uk> wrote in message
>
> - 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
geraldthehamster
spuorg...@gowanhill.com
> Two small bathrooms, one above the other, in a dormer bungalow under
> redevelopment. Both need extractor fans
You could combine ducts and then have one fan sucking from both
rooms.
You would need double-pole light switches in each room, one pole
switches the room light and the other pole switches the fan. This
stops the light in bathroom B coming on when someone switches on the
light in bathroom A.
This was discussed, and I drew a diagram, at
http://groups.google.com/group/uk.d-i-y/browse_thread/thread/98f7dd24859ce778?hide_quotes=no#msg_e98ccf3538d8d9fb
Owain
David in Normandy
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. Davidin...@yahoo.fr
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted
by a filter and not reach my inbox.
geraldthehamster
> You could combine ducts and then have one fan sucking from both
> rooms.
I could, but that's not my plan - I already have a ceiling fan in
place in the upstairs bathroom, waiting to be connected to the
chimbley, which is also in place.
David in Normandy wrote:
>I've recently fitted a bathroom fan that vented to the eaves space. I
>found two problems:
I'm not surprised you had condensation and damp if you were venting
into the eaves. I propose to vent to the outside.
Thanks for all the thoughts, but I'm still hoping someone knows
something about my specific question, concerning two fans blowing up
two ducts that meet at one chimbley ;-)
http://oscarthecat.fotopic.net/p54956795.html
Regards
Richard
meow...@care2.com
I dont know what regs say on this, but I do know that if you used one
bathroom regularly and dint use the other often, you'd end up with a
mouldering ring of water in the unused room, so its not a problem free
solution. This is because condensation occurs in the tubing, and runs
down to a trap at the fan. Dont opeatye one of the fans, and the
trapped condensate just builds up and gets ugly. So... I wouldnt do
it.
NT
BigWallop
Sorry about cutting off at the crucial moment, but got called away.
Your proposal to connect two vents into one is difficult to make properly.
It has been tried and tested many times, in many ways, by many others in the
past. They have all fallen into the trap of having both bathrooms fill with
the damp air from the other. If you are thinking of a straight connection
between the two systems, then you'll need to allow a drip trap at the very
bottom of the chimney stack to catch the water that condenses in the pipe.
To make connection between the two systems work properly, you need to bring
the lower system up to near the top of the stack. A bit like having two
separate systems, but sharing just the last bit of stack to the outside.
That way, the two systems are creating separate chimney effects (drawing
warmed air upward) on their own terms. They just join to the last foot or
so of the vent to the outside.
One system passing the other on a straight connection, would need valve type
systems to prevent them blowing air back into the room. One way flap valves
can be created using bits of plastic and things, but they usually fail to
stop all the air from being distributed between the two areas. Which is
what you need create on venting systems like the one you want.
What you want to create is a natural chimney effect from both rooms, then
create a way to force the air up the stacks to remove any moist air more
quickly when the rooms are used to shower and things. If created properly,
the system should actually draw air through the rooms without the need for
fanned assistance. The fans are only used when the air in the rooms needs
to be extracted more quickly.
If you can get both system to connect in this way, and a simple test for
this is a smoke match used to test flue systems, then you have a properly
working ventilation system. If any smoke from the match blows back into the
other room, then the venting is going to be worse when the fans are in use.
The systems will need to be tested both without fanned assistance and with
fans running, both individually and together. If any smoke testing shows a
blow back into either room, the system has failed.
Smoke matches can be got from any good plumbers merchants or Gas Supply
showrooms.
Good luck with it.
David Hansen
geraldthehamster <ric...@zulu.myzen.co.uk> wrote this:-
>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.
It is possible. There are Y connectors which will join two runs of
ducting into one. They have a flap valve which blanks off the unused
duct if one fan is running or is in a mid position if both are
running.
>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?
It is better to have a separate vent, provided that this vent is not
a means of letting water into the structure of the building due to
inadequate installation.
No matter which way you do it, since the ducting is vertical you
should take precautions against condensation.
--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
geraldthehamster
replied. I'll go with the separate vent and chimbley, which will in
any case be less fiddly to contrive.
Concerning condensation within a vertical vent that passes through a
cold roof space, should I pack insulation round it?
Regards
Richard
BigWallop
bottom of a vertical stack to catch any condensate that trickles down the
vent. Something that you can clean out and dry off when it needs it. We
used to put a cap end on the bottom of a 4'' pipe stack being used as a
vent. It lets you unscrew the bottom off and dry it.
David Hansen
<spam....@good-spam-guard.com> wrote this:-
>You do have to allow a water trap at the
>bottom of a vertical stack to catch any condensate that trickles down the
>vent. Something that you can clean out and dry off when it needs it.
Manufacturers offer water traps which fit into a vertical duct just
above the fan. These have a water outlet which is intended to be
connected to a suitable drain.
Mark
<ric...@zulu.myzen.co.uk> wrote:
>To clarify, these are my two options:
>
>http://oscarthecat.fotopic.net/p54956795.html
Option 2. Always keep tube lengths as short as possible.
--
(\__/) M.
(='.'=) Owing to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking most articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.
See http://improve-usenet.org