I have an older home that I want to install a bathroom fan into. Is it ok
for the exhaust air to duct into the attic, or must it be ducted to to the
outside of the house through the wall. If it can just be ducted into the
attic it will save a lot of effort.I can't imagine a small amount of
moisture messing up the attic.
It is not OK. I can cause serious damage in the attic. Warm moist air
up there can do a number of very bad things. You want the fan to move that
moisture out of your home, not just move the problem to a different part of
If you had done a search for bathroom fans or ventilation within this
group, I'm sure you would have found a number of strings discussing
Mr. Meehan has summarised the issue nicely.
The first two respondents took care of the "where to vent" question. I'll
add this: There are a few different sizes of fans for bathrooms. It makes no
sense. Get the one that moves the most air. Don't even think about noise
level. When you finish your shower and the bathroom's almost totally devoid
of steam, you'll be glad for the noise of the fan.
Personally, since my toilet is in a separate enclosure than the shower,
I blast the shower air into the rest of the house, which
desparately needs the humidity anyway. During the summer, I have to
stop doing that.
Why? Say 1.25 gpm of 105 F water comes out of the shower for 10 minutes,
and the bathroom air is 70 F at 50% RH to start with, and we a) run a
50 cfm fan during the shower and afterwards until the bathroom reaches
60% RH, or b) run it afterwards until the RH reaches 60%...
First of all is this bathroom used for showers?
If not, you can definitely vent in the attic.
If so, in spite of all oter advice, it would appear to depend on the
attic venting and how well the attic is insulated. We have a fan in a
bathroom used for showers that vents into the attic and have had no
problems. House is now 40 years old. As usual YMMV.
I have an older home (1920) with 2 bathrooms missing fans. What I did
was to get the fan/light combo and cut out the ceiling from the fan to
the wall. I then cut through the outside wall, just above the ceiling
to install a vent. Connected the vent to the fan with a flexible metal
snake tube (think dryer vent). After, patched up the hole in the
ceiling and put a coat of textured ceiling paint over it (hides the
ametuer job of patching). Connected the fan/light to same switch, so
both fan and light come on when switch is turned.
Keeps the bathroom much dryer after showering. Took abolut 2 days to do
each bathroom, between the installation and painting.
Me too. We have two second floor bathrooms with tub/showers whose vent
fans just dump into the attic. I was concerned too, but took our
builder's word that there was adequate attic venting to handle it.
Location is near Boston and the attic is vented by grills all along the
undersides of the front and rear eaves and a ridge vent along the whole
length of the roof.
I had about 25% of the attic "floor space" covered with plywood and put
plenty of lighting up there too. We store a lot of inherited "chatckas"
we can't bear to throw out up there, and go up at least ten times a year
to hunt for stuff or to change filters in the HVAC air handler.
In the 19 years since we had the place built I haven't noticed anything
wrong in the attic.
Just my .02,
Even a small amount of moisture is not good, as water vapor condenses
causing leaks, wet insulation and promotes insects and fungus. I
hated to do it, but I cut a hole in the roof and installed a roof vent
with storm flap and bird screen. I used a generous amount of
tar-based roofing caulk.
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