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In venting my upstairs bath to the outside wall, I plan on using rigid pipe, since once things are closed up, there will be no access to check or fix leaks. PVC sched. 40 seems to be a popular choice, but I need to negotiate some bends, and space is tight slipping under the top plate. (The rafters are 2×12, on a 2×6 wall, so there is more room to go under than over) Is there any reason not to use 4″ exterior drainage pipe and polypropylene fittings? they are 1/4″ less O.D. than PVC, and less expensive to boot. Also, should I worry about warm moist air being vented just below my soffit vents?
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go thru the roof..
we use 4inch galv. with elbows..
check below about twenty threads for
for why NOT to go thru the soffit..
Kermit
*Mike, I had previously read the threads you suggested, and given alot of thought to this. Asthetics aside, I am reluctant to punch any holes in my roof. The accessable roof doesn't have much pitch, and in this section of VT, it is common to have a foot or more of snow up there for long periods. Wouldn't most vents be covered in snow, or get iced, or contribute to ice dams? I also wondered about heat loss if the louver fails. A level or slightly downhill exit might be more neutral to convection currents(?) Given these considerations, does wall venting make any sense? Thanks for your time and thoughts on this.
*well. go thru the soffit then.. but blank off the soffit vents that are ventilating the attic for a couple of feet each side of your bath vent..make sure your fan has enough push to make the down discharge.. and try to make the pitch continuous from a high point to the vent itself so any condensation will flow out the vent...if you have a first floor bath, with another floor above it, use a wall discharge at the end of a joist bay, but if it's the top floor, i would go with a roof jack...look in Graingers for the page on sizing bath vents .. it's a good primer.....i like the Broan series of the last one i did was for a 10x7 bath and i used a Broan S120L. 120 cfm...4.8 sones sound level..frankly i don't have enough experience to tell you about Vermont snow levels...ask some of the contractors around you... i would think a good bath fan blowing 90 deg. air would eat thru any snow you got.... but i been wrong before....
*The idea of venting a fan to a side wall or soffit has come up a few times lately.........and most everyone has said "make sure you slope the pipe so it drains...." Well, in all houses I've lived in, the fans have been vented thru the roof, and all have had the moisture condense and drop into the fan and drop into the bathroom. Is there a way to vent a bath fan thru the roof and not have this happen? I would think if you can vent it out thru a side wall and take advantage of the pipe running horizontally instead of vertically and eliminating getting rained on whenever you've just finished your shower, would be a good thing.Someone please explain how to properly install a fan and vent it thru the roof (w/o leaks).Matt
*just a couple of thots on bath fans..1) i always locate them so they are half in and half out of the tub / shower area... first, they are in the general vicinity of the culprit.. thus can intercept the warm moist air..second. the light from the light/ fan serves as the shower / tub lightnow , IF... moisture is dripping back down from the fan... it drips into the shower /tub2) i size the fan / light so it can actually work.. this is usually in the neighborhood of 100 CFM, i pay extra for the ones that have a low noise level. so the owners will be encouraged to use it..if the warm moist air is actually being expelled and it stays on long enough to get rid of the warm moist air... then there is NOTHING TO CONDENSE.. so nothing drips back in3) we always put the fan & light on seperate switchessometimes when it is really cold ... like 10 deg F... i can hear the fan laboring for awhile... then the sound levels off... i think the damper is probably frozen shut ... and the warm air defrosts it... the damper opens and the condensation clears... if you experienc a lot of much colder air than us .. i would try to keep the runs straight and insulate the pipe so the air can retain its heat (and thus its moisture ) as long as possible.. no temperature drop... no condensation... no drip..b but hey, whadda i know?
*When we install fan/light combinations we always put a small dip in the line just after the fan to collect condensation if it occurs. Try a timer on the fan to let it run long enough to expell the moisture.Run the vent out the gable end or thru the roof and extent the pvc up a ways with a 180 degree cap (like a furnace vent).
*What I didn't admit to in my first post is that the hole is already cut through the (log siding) wall, so I'm kind of committed... not impossible to undo, but not easy. The pitch that the vent pipe will run at is a straight downward shot at 18 deg. Looking at it now, I can see that the soffits are just waiting overhead to suck up that warm moist air. Maybe if I made a deflector: a piece of plywood over the soffit vents, but set off an inch or two so they can still breathe the good air around the ends...You all brought up the subject of fan placement. I'm using a nutone ultra quiettest. It's mounted in this large metal housing with punch-outs for the brackets and wiring. Since this is mounted in the ceiling, essentially surrounded with insulation, my thinking was not put it directly over the shower for fear of steam penetrating the fan housing and soaking the insulation. I'ts a real quiet fan, but I can't count on it always being used. On the other hand, it makes sense to put it close to the source, and it's actually one of the easier spots to work with in this tiny (8x8) room. The other spot is over the stool, which is the other "source". Whaddya think?So anyway, my original question was about plastic pipe. Mike suggests the galvanized. This would work well for me, but will it be as watertight as plastic, and will it hold up to moisture? The galv. pipe I use for my maple sugaring stove is pretty rusted, but thats outside....... Hey thanks for all your ideas.
*Tom,As I noted in earlier threads, I use 4" Schedule 30. Works for me. No reason why it should not work for you.Steve
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In venting my upstairs bath to the outside wall, I plan on using rigid pipe, since once things are closed up, there will be no access to check or fix leaks. PVC sched. 40 seems to be a popular choice, but I need to negotiate some bends, and space is tight slipping under the top plate. (The rafters are 2x12, on a 2x6 wall, so there is more room to go under than over) Is there any reason not to use 4" exterior drainage pipe and polypropylene fittings? they are 1/4" less O.D. than PVC, and less expensive to boot. Also, should I worry about warm moist air being vented just below my soffit vents?