Replies

1. 
   Michael_Leisitko/Builder | Mar 09, 2000 06:06pm | #8

   *
   Steven:
   We vent into the soffit quite often on new construction. I try to limit roof penetrations when possible. We use round galvanized vent pipe that has a positive connection to the soffit vent. We typically use 8"x14" louvered individual soffit vents. The piping is taken to the rectangular soffit vent and set to the inside face of vent. Yes the galv. pipegal.nsulated while in the attic space. There is no room for air to slide by the soffit vent on this type of connection. Our building inspector gives it his blessing also.

2. 
   Guest_ | Mar 09, 2000 06:19pm | #9

   *
   Stephen,

   FWIW, I think going through a soffit would be most likely to work, but no guarantees.

   As a home inspector, I see lots of different installations and find it hard to draw any hard and fast rules.

   Many times I see them exhausted into the attic, nailed off to a rafter with no external vent source nearby, yet with no signs of mold or condensation. (Maybe they're lucky, maybe they don't use the bathroom fan.)

   I see many which run the vent under the insulation between the joists and terminate _by_ the soffit vents. Usually I don't see adverse signs, every once in a while I'll see some mold there.

   I think the major concern with your plan is finding a spot in the soffit which doesn't happen to have positive pressure from wind currents around the house. I don't know of anyway to figure this one out.

   FWIW, the houses I'm most likely to see mold on the roof sheathing are hip roofs with relatively low pitch and no soffit vents. The north plane is the most likely spot. (50's ranches, for example.)

   I suspect that the house you're discussing doesn't have too low a pitch if it has cedar shakes.

   Bob Walker

1. 
   Guest_ | Mar 09, 2000 09:53pm | #10

   *Gentlemen. the ideal way to vent a bathroom exha ust fan is either in a wet wall with the duct works running down ans out through the joist header, of through an exterior wall.Venting through a roof adds another penetration through the roof which leads to eventual leakage. In the snow belt it may be covered with snow for most of thw winter. The rising moist warm air can condense on the duct's walls and the condensate run back inside. The result is the tell tale drippimg, staining and ru sting. The stack effect--warm air rising--keeps a constasnt stream of warm air rising, which keep the backflow valve constsantly open.This is more common than realized.If the only place the fan can me located is in the ceiling, it must be exhausted through a gable wall. Use an elbow to raise the duct above the fan and slant the duct downward and exit it through the gable end wall. Use a wall cap that has a spring-action flap. Stephen's problem is he has a hip roof which means no gable walls. He's said through the roof is out of the question. This leaves soffits. He notes there are no soffit vents. so he must exhaust through the soffit.Therefore install the vent in the south soffit.As noted the problem with exhausting through a soffit is the real possibility of mold developing in the unvented soffit and the wall. With avented soffit you get in addition to the potential mildew and staining of the soffits, thje exhaust from the bathroom fan will be sucked into the attic by the air flow through the soffit vents. GeneL.

1. 
   Guest_ | Mar 09, 2000 10:03pm | #11

   *How about a wall mount vent? Jeff

1. 
   Guest_ | Mar 10, 2000 04:21am | #12

   *Well I live in a house with both a wall vent and a bath vent. In fact this question was in another post recently. It's no big deal to put a vent in the roof if done properly. Sure when it snows there is some caving untill the exhaust breaks out. But that is it.As for the soffit vent; Don't do it unless you want all the mold rot etc from the trapped moisture. Same for the shortcutters who just vent into the roof cavity.

1. 
   Guest_ | Mar 10, 2000 05:34am | #13

   *Stephen,Why not through facia?KK

2. 
   Guest_ | Mar 10, 2000 01:57pm | #14

   *Gene,Thanks for taking the time to explain your point of view. While I don't agree with everything you said, I always like to hear other's opinions that either agree or disagree with mine.Red dog

3. 
   Guest_ | Mar 10, 2000 03:36pm | #15

   *Thanks for the clarifications.Rich Beckman

4. 
   Guest_ | Mar 10, 2000 03:46pm | #16

   *I was just told by my inspector that through soffit was what he wanted to see and as long as the fan has a vent flap, the exterior could be rigid mounted as we saw fit. We used pvc for the piping and a striped down (no louvers) dryer exit to keep the birds out, works fine, looks good, and with the pvc theres no worries of the plastic dryer type hose rotting.

5. 
   Guest_ | Mar 10, 2000 11:39pm | #17

   *Red dog. I'm glad we agree to disagree. GeneL.

6. 
   Guest_ | Mar 12, 2000 07:59pm | #18

   *Chris R.,I have a hip roof house plan that gets vented as you describe. I built one several years back under the "Super Good Cents" guidelines and was required to close up the continuous soffit strip vent for a distance of three feet on either side of the vent termination. Another that was built using vinyl soffit received solid panels for the same three feet on either side. I have followed the same reasoning for wall terminations for propane heating stoves and water heaters that vent through a wall next to a soffit vent.(within three feet.) The moist air could be carried up through the venting and condense in the cold attic.

7. 
   Guest_ | Apr 03, 2000 05:36am | #19

   *What about venting to a ridge vent if there is one? The negative air flow should suck it outside, no?

3. 
   Guest_ | Apr 03, 2000 05:36am | #20

   *
   i've been asked to install a bathroom fan in a house with hip roofs, i.e., no gables. anyone know of any reason(s) why i can't put the vent through a soffit? really really don't want to go through the roof on this one...

   thanks

1. 
   Guest_ | Mar 08, 2000 11:42pm | #1

   *Stephen, Through the roof is a no-no. And exhausting through a soffit is another no-no.If the soffit overhand is not vented mildew and staining will take place on the soffit and the wall. If the soffits are vented, the exhaust from the attic fan will be sucked into the attic, where it is not wanted. If the only way to go is through a soffit do it in an unvented soffit.GeneL.If you must .

1. 
   Guest_ | Mar 09, 2000 12:35am | #2

   *Gene,Where do you exhaust ceiling bath fans with attic space right above? The roof is normally the closest exit and whatever moisture comes out is hitting the roof, which can handle it. I go through the roof whenever I can with rigid pipe with insulation wrapped around it. I'm having a hard time with the put it in an unvented soffit part of your response. Please enlighten me.Red dog

1. 
   Guest_ | Mar 09, 2000 07:11am | #3

   *Gene,You say not through the roof, and not through a soffit vented or not. You grudgingly say do it throught the unvented soffit.Where would you vent it to happily?Rich Beckman

1. 
   Guest_ | Mar 09, 2000 01:07pm | #4

   *There is a plastic vent made to be mounted in a soffit. I've never seen the mold problem but I live in a cooler climate.

2. 
   Guest_ | Mar 09, 2000 03:27pm | #5

   *I can see how going through the roof could be a problem if you get snow.

3. 
   Bruce_Siuta | Mar 09, 2000 03:40pm | #6

   *I am a professional Roofer. On residential shingle work, I always check the attic or roof space for adequate venting. More often than not, I see kitchen and bath fans vented directly into the roof space, usually with a substantial amount of mold and mildew nearby. I re-fit the fan exit with solid aluminum snap together duct, seal all joints with duct sealant (no duct tape!),and wrap unfaced fiberglass insulation carefully around the ducting to prevent condensation from forming inside the duct. I always go through the roof, with a duct hood made just for this purpose by Newtone, available at electrical supply companies that carry Newtone products. The hood is also aluminum, with a foam gasketed,gravity blow-back cover. I prime and spray-paint the hood to match the roof. It is installed under the top and side shingles and over the bottom shingles, with a generous amount of sealant between the duct flange and the roof. I try to place it facing away from the prevailing wind direction, high on the roof but at least three feet below the ridge. Snow isn,t a problem, there is always enough residual heat from the interior of the house to keep the duct exit ice and snow free. Even on roofs that are not getting re-shingled, it is a fairly easy procedure. I have done about 15 of these retrofits, all worked out great !!

4. 
   Guest_ | Mar 09, 2000 04:12pm | #7

   *brucei am not a professional roofer, and i got to tell you that the idea of going through a cedar shake roof here in boulder, co (wind storm last night with gusts clocked at over 100mph) does not excite me at all. and gene, as for exhausted air from the bath getting back into the attic space through soffit vents- not a problem since there don't appear to be any vents at all in this attic, soffit or no. all i want to do is pop a little louvered vent through some soffit on the leeward side. no problems with it being directed groundward, right or wrong? and bruce, while you brought it up, is the reason to insulate the duct to keep cooler house air from causing condensation in the attic, or to keep cooler attic/outside air from entering the house ( and i think i may have just answered my real question, which is should i use insulated duct...)?