venting a bathroom fan

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one of my projects this fall is to update the wiring upstairs in my house. I plan on replacing all the ceiling boxes with fan-rated ones, dropping 14/3 switch legs to all the wall boxes for fans, and replacing all wiring with 14/3 Romex. Also pulling one new 14/2 homerun to provide for two separate general circuits (original homerun is 14/2 BX so it is grounded and doesn't need to be redone) and a 12/2 homerun for the bathroom. While I'm at it I would like to add a ventilation fan in the bathroom to pull out the condensation while showering (currently using a window mounted fan) but I am not sure how to vent it.
I don't want to use a conventional stack through the roof as the roof is aluminum "shingles" and it appears a) hard to work with and b) hard to walk on without damage. So I was thinking of using a dryer vent type thing through the side wall of the attic. My question is, is this acceptable by code, and even if so, are there any drawbacks to doing this?
thanks,
nate
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Unless you have local codes preventing it, that is how most bath vents are done in my area. Do use something other than plastic dryer vent for the duct. The smoother the better, with the least amount of bends. If you locate the fan directly over the tub, it'll need GFCI protection

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It'll be outside the tub (was thinking simply dead center in the ceiling,) but I plan on running everything through a GFCI anyway (since my mental plans call for a three gang switch box with light switch, fan switch, and GFCI receptacle.) I suspect that one 90 degree bend will do it, would you use rigid metal duct or PVC? 3" or 4"?
Also due to the age of the house I think a metal fan housing would be appropriate, either nickel, chrome, or stainless. any recommendations for a high quality fan unit that would look right in a late-40's house?
Another option would be a through-the-wall unit with a louvered vent, are those still made? Although I am thinking that the ceiling might be better as there is limited wall space in the bathroom and I'm sure SWMBO will eventually want to hang some pictures or other decorative froof.
thanks,
nate
RBM wrote:

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Any good fan is going to have a 4" duct, I'm partial to the Ultra Quiet Broan fans. I usually use aluminum vent pipe, but plastic would be great as well

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Actually the "good" fans that are also quiet use 8" I am very happy with the panasonic fan I installed recently. It makes the others sound like a blender.
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beecrofter wrote:

Have been doing a search, got another idea - what about using a remote inline fan in the attic, with a simple grille in the ceiling? It would seem that that would make for quieter operation.
nate
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wrote: <snip?

In my previous house I installed two Fantec inline fans with lighted ceiling grilles in two bathrooms. They were more expensive than standard fan/light units, but unless it was absolutely silent in the house you couldn't hear them running, yet they moved more air than most small built-in units. They come in different CFM ratings, so you choose the appropriate size for your room (guidelines on their web site). I ended up with one 100 cfm and one 150 cfm.
Since I live in NE Ohio, I used insulated flexible ducting between the grilles and the fans, and between the fans and the sidewall jacks. I think the insulated ducting helps quiet them as well, and if you choose a fan a little larger than you need, the extra resistance of the flex duct won't matter. It's way easier to install than rigid ductwork.
I'm with you, I prefer to run out a side wall; less chance of leaks.
I put them both on electronic timers so you can set the fan to run for a few minutes after using the shower to clear the humidity.
I will definitely go the same route when I do my existing home.
Good Luck,
Paul F.
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Paul Franklin wrote:

thanks for the input, I'm starting to think that this may be the way to go although I do not need a light in the ceiling (small bathroom, light already on wall over medicine cabinet)
I like the idea of a timer as well, I was already thinking about that. Would be nice in the morning to set the timer before getting in the shower, and then if I leave the house shortly after the fan would still keep running for a while. It appears that Nutone makes one, but I can't find a picture of it - anyone know if it fits in a standard Decora switchplate and if not, if there is one available that does?
thanks for the ideas, keep 'em coming...
nate
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on 8/25/2007 12:04 PM Nate Nagel said the following:

It's not necessary to change the fan, just the switch. http://www.nextag.com/bathroom-fan-timer/search-html
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In Hamptonburgh, NY
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Nate Nagel wrote:
...

Intermatic (as do others) makes a variety of timers that replace wall switches, both electronic and mechanical. I believe that the electronic ones may need to have a neutral in the junction box. The mechanical ones are just simple two wire hookups. I have replaced a number of fan switches with timers.
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Yep-- Fantech makes a great one: http://www.waveplumbing.com/store/index.php?main_page=product_info&products_id006 I installed one of these and while it's overkill for my fan (it's rated for 20 amps, my fan is 18 watts) it's the best timer switch I've ever used. Hit the 30 min button when you enter the shower and forget it. It's also lighted, so it's easy to see it in the dark and/or tell how much time is remaining.
It's white and comes with a Decora plate.
-kiwanda
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I agree, those remote Fantechs are really nice, when I've used those I use 4" PVC to duct them. I'm not a real Panasonic fan, especially not with an 8" duct, but they are silent

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RBM wrote:

OK, so it looks like my options are either a small remote Fantech unit, or else a Panasonic ceiling unit, either one vented through a 4" duct to a dryer vent type grille on the side wall of the attic. Pros/cons of either? Other options I should be looking at? Bathroom is only 5x7 so I would assume that 4" duct would be fine.
Fantech recommends insulated flex for their units, so that is what I would probably use. If I used the Panasonic I imagine I could tuck everything between the ceiling joists so it would end up being covered by the existing cellulose so I could use smooth metal or PVC.
Looks like my idea of finding a vintage-looking grille just isn't going to happen so I should suck it up and deal with white plastic.
thanks,
nate
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wrote: <snip>

Maybe you could use something like this as the grille over the housing that comes with the Fantec. The plastic grill just snaps in, you don't have to use it. The backdraft flap is part of the housing, not the grille.
http://www.crafthome.com/subsidiarypages/registers/opera/operaMainFramePage.htm
(Click on 6" round opera grille after the page opens)
A little pricey, but definitely vintage looking.
Paul F.
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Nate Nagel wrote:

Broan makes a roof or gable mount where the blower and motor are mounted while the vent is ducted. That way you don't hear the "motor" in the bathroom.
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RBM wrote:

A word of caution when using plastic vent pipe. Be sure it is not exposed to sunlight through eave vents or doormer vents. The UV destroys the plastic [the 4" plastic vents are not UV protected.]
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Absolutely. Among the best are Panasonic's "WhisperWall" model: http://www.waveplumbing.com/store/index.php?main_page=product_info&products_id 8 These draw only 18 watts and are <1 sone so you really don't notice the noise even though they pull 70 CFM. I put one in my 1957 cape to avoid cutting into the plaster ceiling. It was a simple job, the fan comes packaged with a very nice outdoor vent and good instructions. Great improvement over the old unvented bathroom, and it took less than two hours total including running wire and installing a new timer switch.
-kiwanda
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Absolutely. Among the best are Panasonic's "WhisperWall" model: http://www.waveplumbing.com/store/index.php?main_page=product_info&products_id 8 These draw only 18 watts and are <1 sone so you really don't notice the noise even though they pull 70 CFM. I put one in my 1957 cape to avoid cutting into the plaster ceiling. It was a simple job, the fan comes packaged with a very nice outdoor vent and good instructions. Great improvement over the old unvented bathroom, and it took less than two hours total including running wire and installing a new timer switch.
-kiwanda
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Some tips about bathroom fans (condensation issues, bends, etc.) here:
http://www.askthebuilder.com/546_Bathroom_Fan_Ventilation.shtml
And stolen without permission from http://tamtech.com/faq.htm#b5
***** Begin Included Text *****
Questions about bathroom fans
What is a reasonable amount of air flow from a bathroom fan?
An installed airflow of about 100 cfm run intermittently should suffice. Installed performance will be below the label on the box. To achieve 100 cfm installed, the rating on the box should be 125 to 150 cfm. Too much ventilation is bad when it dries out the house and wastes too much energy, but for occupant health, too much is better than too little.
How can I tell if my bathroom fan is working properly?
There is a simple test you can do yourself to determine if your bathroom fan is working properly. From six inches away, squeeze a cloud of baby powder from its container toward the intake grille of the operating exhaust fan. If the fan is working properly, the powder will be drawn up into the grille. If it goes to the center of the grille and is blown back into the room, then the fan is blocked; if the powder simply hangs in the air, the fan is not working at all. Its just making noise!
Where should I exhaust the air from a ducted bathroom fan?
Always exhaust the air all the way to the outside. Do not dump it into the attic. Be sure to use insulated duct in unconditioned spaces such as attics.
My bathroom fan is sometimes very noisy. Why?
Fan noise goes up with increases in pressure. Fan performance will decrease as the fan ages.
Any other tips for bathroom fan installation and performance?
Sure!
If the bath fan is mounted on the attic floor and has a plastic duct attachment nozzle, the plastic may soften in the hot attic. So don't clamp the ducting to tightly or it can deform the nozzle and cause the backdraft damper not to work.
Often the first turn of the ducting system is the worst turn. Moving that turn away from the fan and easing it will greatly improve the performance.
Flex ducting is twice as restrictive to airflow as smooth ducting. Increasing the diameter of the duct by one inch will reduce the resistance by about 40%.
***** End Included Text *****
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Nate Nagel wrote:

Doesn't sound like you're in cold climate, but if so, you have to watch for condensation inside the vent "hose" running back into the fan or leaking out into the attic.
Jim
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