Replies

1. 
   bbqjason | Mar 19, 2005 10:32pm | #1

   if you vent out of the soffitt, chances are that moisture will get sucked right back in through the soffitts and into your attic.  you can't take it through the roof?

1. 
   kkj | Mar 19, 2005 10:42pm | #3

   Phoenix area, low humidity, soffit vents are minimal due to gable end design and gable vents.

   Also prefer to reduce number of roof penetrations in tile roof.  Walls are ICF, 6" of concrete.

   Thanks for the reality check

   -K

2. 
   Hubedube | Mar 19, 2005 11:21pm | #6

   A soffit mounted vent opens when the fan is on . When the fan is off the flappers on the vent close.

   No air will ever be sucked up into the attic,etc.

   These soffit type vents are like an inverted 'T' with a gravity operated flap on each side of the T. The exhausted air is discharged on a downward angle ...They work great!

   No need to ever go thru a roof.

   Edited 3/19/2005 4:24 pm ET by Hube

1. 
   kkj | Mar 19, 2005 11:39pm | #7

   I think what bbqjason was referring to was the warm humid bathroom air vented through the duct, being warm and humid, rising up through ventilation vents in the soffit into the attic

   Maybe a valid concern in cooler climes.

   I don't believe it to be a real factor in Metro Phoenix where the bathroom air being blown out will be cooler than the ambient outside temperature 5 to 6 months of the year.

   I would also suspect that mixing and dilution of the discharged air likely makes the question of adding  significant humidity inside the attic a non-issue except maybe in extreme winter locales, maybe not even there.

   I have been wrong before, just can't seem to remember when.

   -K

1. 
   DanH | Mar 19, 2005 11:56pm | #8

   Yeah, it think the backflow into the attic is more a theoretical concern than a practical one, and just to be sure one can block the soffit vents on either side the fan vent for a foot or so.

1. 
   zendo | Mar 20, 2005 12:32am | #9

   lol

   Its very common that half the roof has to be torn out, including framing members because of mold and moisture damaging in a cone shaped formation from the soffit to the ridge, but what the heck, he'll probably charge it to his INS.

   -zen

2. 
   DanH | Mar 20, 2005 12:48am | #10

   If that happened I'd have to believe that the moisture was escaping the ductwork inside the roof, and there was a general lack of decent ventillation. Even if some condensation does briefly occur, it should evaporate within an hour max if ventillation is sufficient.

3. 
   NickNukeEm | Mar 20, 2005 12:59am | #11

   I did a bathroom reno in Dec and replaced the soffit exhausted fan with one directed thru the end wall.  The attic above the soffit vent showed absolutely no signs that a fan was directly below.  This is SE Conn along the shore, the house was about 50 yo (and the fan was original and still working, barely.)  It might be a matter of location, weather patterns, and circumstance that dictates whether or not moisture will be redirected back up into the attic, but I always recommend a side wall if one is available.

    I never met a tool I didn't like!

2. 
   DANL | Mar 20, 2005 02:44am | #13

   Dryer vents aften have those spring-loaded back draft preventers (keeps squirrels out of the dryer too).

1. 
   kkj | Mar 20, 2005 07:24am | #14

   Appreciate all of your comments, except maybe zendo's (putdowns for the simple sake of appearing brilliant are seldom helpful, constructive, or intellligent).

   I didn't run across any spring loaded dryer vent backflow preventers, and I looked for anything spring loaded.  I did find some gravity operated plastic inline backflow flaps, but wanted something at the discharge point rather than further inside.

   I have already ordered the soffit vents that calvin referenced.  As for mold and mildew, I doubt very much that it is going to be a problem.  My last house in St George, Utah had the bathroom vents terminated next to the soffit vents, not outside the soffit (certainly not a recommended practice) but it was never a problem.

   I will have open access to the entire exposed roof inside the attic.  It may be a little difficult for those from the midwest, northeast, northwest, Atlantic coast, West coast, and South to comprehend, but you really have to work at mold and mildew in 8 to 15 % humidity.

   Thanks again,

   -K

2. 
   DANL | Mar 20, 2005 06:57pm | #16

   Come to think of it, when I installed one on my fan vent (in the soffit--but my soffit is not tied to attic) the flapper was a series of like five parallel flapps on a pivot that worked by gravity. I suppose you could rig up a spring or rubber band to one.

   I agree with you about comments that put others down to inflate one's own ego--not very helpful. I especially like it at my church when before one of the "Christians" puts me down they preface it with, "Now, I'm only telling you this for your own good." When I hear that I think, "Get ready for the knife in the back (or the front) "Here, Godfather, this is for you....". I worked at one job where I knew when Emily had just stabbed me in the back because she'd come up and hug me and massage my back--like she was checking to make sure the knife was there (and in deep enough--maybe give it a little twist). And I just got back from church! (Not my usual though.)

3. 
   Hubedube | Mar 21, 2005 12:16am | #18

    approx 99 % of the moist air will be exhausted downward with such a velocity (100cfm) that it will never enter the perforations of the soffit panels.

2. 
   calvin | Mar 19, 2005 10:33pm | #2

   http://www.rewci.com/rewilliams/plsovefor4or.html is the first one a search turned up.  They mention Fantech on the page.  Fantech is a good exhaust fan co.  If you can, check out fantech for appropriate vent cap/hood.  http://www.fantech.net/

   Remodeling Contractor just outside the Glass City.

   Quittin' Time

1. 
   kkj | Mar 19, 2005 10:44pm | #4

   Thank you very much Calvin.

   That will do nicely.  It isn't the kind I remembered, but it looks like what I need.

   Don't know why my Google search for soffit vent didn't turn up that link.

   Thanks again.

   -K

1. 
   calvin | Mar 19, 2005 11:13pm | #5

   You're welcome and welcome to breaktime.  Ever in ohio, buy me a beer.  If I'm ever in arizona, I'll be by.

   Do check out the fantech site, some options you might not think of.Remodeling Contractor just outside the Glass City.

   Quittin' Time

3. 
   gdavis62 | Mar 20, 2005 02:14am | #12

   Did you check out the specs for your fan?  I use Panasonics, and they all have backdraft dampers in the units.  That means to me that I don't need a flap on the exterior outlet.

1. 
   kkj | Mar 20, 2005 07:28am | #15

   My fans also have flaps at the fan housing, just wanted something out at the discharge point to help keep small critters out of the ductwork.

   Thank you for the input

   -K

4. 
   Hubedube | Mar 21, 2005 12:12am | #17

   Run your 4" exhaust pipe or flex from the fan up  to the soffit and attach a flush mounted inverted T plate. (they are approx $8.at some hdw stores.) the backdraft flaps are built in. It measures only about 6" x 6" so it will install onto most soffits.(2 screws)