"Joseph Meehan" wrote in message
...
"marson" wrote in message
s.com...
On Sep 22, 10:20 pm, "John61" wrote:
Our two-storey house has a washroom on main floor, and it has no exhaust
fan. Don't want to make a fan on exterior wall (direct vent out), as our
winter is too cold.

I'm thinking to place a fan into interior wall, and get duct up to attic
inside drywall, then vent out from roof. I wonder if this is feasible.
Are
there exhaust fans thin enough to fit into interior wall which is only
4-5"?
Is this too big a job to make through from main floor to attic (e.g.
drill
holes on 2x4s)? If doable, I may pay to get an expert to do it.

Any input appreciated.

John

John, I think you should put the fan on an exterior wall. Yes, it
could be done like you describe but this approach has several
disadvantages: first, you will have a lot of piping and thus friction
loss. Worse, the vertical exhaust out your roof will be prone to
condensation--this will be exacerbated by the distance from the fan--
as the exhaust air cools, it will be more prone to condensation. This
condensation is going to run right back into the house and cause all
sorts of problems. I once put in a through-the-attic bathroom fan vent
and I never did successfully stop it from dripping in extreme cold
(-30 F). I had it well insulated, but there is of course no way to
insulated the portion that pops out of the roof. Further, you will
have a heat loss from your bath fan no matter where you put it. With
your tall pipe to the roof idea, it may even be worse because you will
create a draft situation. Put it on the wall!




I agree. The wall exhaust should have a flap on it to reduce the cold
air problem.

Note: no matter what, when you use an exhaust fan, there is one cubic
foot of outside air coming into your home for every cubic foot of air you
are exhausting. I like being about to exhaust or not. I use the exhaust
more during temperate seasons and less during hot humid summer or cold
winter.

--
Joseph Meehan

Dia 's Muire duit


This depends on the house, of course, but here, if the heat's just kicked on
in the morning, it usually runs a bit longer than a shower. No need for the
fan. The bathroom stays dry. I'm talking about HERE. May not work in other
houses, with other routines.