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In a bathroom as small as this it doesn’t much matter where you put the fan. The big problem is Switching because most people leave the fan on only when they’re in the bathroom. They also shut the door after they leave. This creates a situation where you are hoping to vacate all the humid air as well as all the air which will become humid after the walls evaporate their moisture away, only during the time you are in there. This is pretty much an impossible situation. In other words, you can get rid of the cloud in the room while you shower, so that you can shave just afterwords, but after you leave and shut the light/fan off, it will get humid again and stay that way for long time (30 to 45 minutes).
I suggest a timer switch, even if they are unsightly. If, as in a tenant situation, you are concerned that people will not think to use it, you should tie it into the light switch too.
As far as venting through the attic, you are probably aware that condensation will often occur within the duct. Use stovepipe ductwork and limit flexible vinyl to as little as possible. I usually don’t worry about the condensation cause any bacteria which could develop are headed outdoors anyway. You might want to slope the ductwork towards the exterior vent.
As far as products go, cheaper could mean noisier and you should ask a salesperson about this. In general, they are so inexpensive that you don’t have to be too worried about lifespan of the unit. Best of luck.
Replies
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In a bathroom as small as this it doesn't much matter where you put the fan. The big problem is Switching because most people leave the fan on only when they're in the bathroom. They also shut the door after they leave. This creates a situation where you are hoping to vacate all the humid air as well as all the air which will become humid after the walls evaporate their moisture away, only during the time you are in there. This is pretty much an impossible situation. In other words, you can get rid of the cloud in the room while you shower, so that you can shave just afterwords, but after you leave and shut the light/fan off, it will get humid again and stay that way for long time (30 to 45 minutes).
I suggest a timer switch, even if they are unsightly. If, as in a tenant situation, you are concerned that people will not think to use it, you should tie it into the light switch too.
As far as venting through the attic, you are probably aware that condensation will often occur within the duct. Use stovepipe ductwork and limit flexible vinyl to as little as possible. I usually don't worry about the condensation cause any bacteria which could develop are headed outdoors anyway. You might want to slope the ductwork towards the exterior vent.
As far as products go, cheaper could mean noisier and you should ask a salesperson about this. In general, they are so inexpensive that you don't have to be too worried about lifespan of the unit. Best of luck.
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Look at thread called "return air in batroom[sic]."
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Great idea, install a powered bathroom vent. I love them. As the other guy said they are only effective if you turn them on. I fight with my parents about this. They don't use the one I put in their bathroom. I always put in a separate switch for the vent so I can leave it running from the time I get in the shower until I finish eating and dressing and am walking out the door in the morning. They don't use much electricity and the heated air they exhaust in the winter isn't that valuable. If your shower, tub and toilet are at one end of the bathroom put it at that end of the bathroom. I have twice used and like the Broan 3.0 cfm, 2.5 some(noise) model, I think these numbers are about right. Its about $100 at the local warehouse amateur fixer upper stores. As for going through the gable instead of the roof, how often do you see a dryer vent on the side of a house instead of the roof? All of the time so its OK to put it through the side of the house instead of the roof. Shortest amount of pipe is best.
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Pleased to hear someone else has such a ... cozy bathroom. I installed a small Nutone 50 CFM unit in the ceiling, just 0.3 sones (all but silent), about $90. Ducting up around the band joist and out the rake for easiest cutting. I had to use flexible vent because the fan was designed for houses that have overhead access. Lacking that I attached the vent and raised/screwed the fan housing into the joist space, then pulled duct into upstairs closet to duct outside. Fiberglass & plastic jacket on duct, and I will check for condensation problems -- I hope to blow cellulose into the band joist space at some point.
I agree with gary, you have to trick people into using the fan. I wired mine on the bathroom's space heater timer -- no fan, no heat. During the summer, I hope the window will be cracked. Used GFCI as fan is over tub (code). I also cut a small louver vent into the bathroom: if the room is sealed too well with the door closed, the fan just won't work, or will draw an unpleasant draft under the door.
For free shipping, great prices and service on Nutone products, try http://www.rinutonedistr.com/finished.htm
*Mike: All prior posts sound like good ideas. They got me to thinking about a few things. Most baths that I remodel are 5'X8' or 5'X10' (max). Pretty common for non-custom homes. Never really thought of them as cozy or small--NORMAL size would describe my experience.Anyway, if you had that 50 sf with 8' ceilings that would be 400 cubic feet. If your fan was rated at 50 cfm (about the smallest you would want to go) wouldn't that exhaust your bathroom in 8 minutes? So after a shower was finished introducing moisture into the room all you would have would be evaporation of the droplets on the shower enclosure and tub or base. I think Russell must have a decimal out of place if he is using a 3.0 cfm fan. Must be 30. You wouldn't want to take more than 2 HOURS to exhaust a bathroom.I agree that a timer would be nice. I was thinking about it more for exhausting noxious odors after the occupant left but it would work for both odor and humidity. Does it really take longer than 8 minutes or less to do an air change? I note that most residential bathrooms are left with the door open after use. A louver or a 24" door undercut by just 1" must supply more cfm than a 50 cfm fan could extract and would make things work well even when closed.Do not overlook the GFCI for the fan as mentioned. Finally, I have gone to using PVC for ducting. It APPEARS to offer less air resistance (friction), won't be affected by moisture and I insulate it with the insulation made for round ducting (also mentioned earlier). I routinely route ducting out the gable. You may want to make sure your cap has some screen (wide mesh) to keep critters out. The flaps can stick, disappear, etc. No need to make a bird house out of your vent! So have I been missing something regarding bath ventilation? If so I'd like to know as I stumble forward for another year?
*To piggyback:Does anyone have experience with or knowledge of fans designed to vent directly through the exterior wall of a bath, thus avoiding ceiling penetrations and several feet of ductwork?Any pro's/con's regerding this? I thought I had read postings sometime ago pertaining to this but couldn't find anything in the archives.
*Mike,et al,some great info for you above, to add to that, sones is the sound rating for fans;lower number, lower noise level, 2.0 or lower seems to be a good level.The fan/light unit should be IC rated(insulation contact)if applicable and rated for wet location.I would always wire it up to a GFCI protected circuit.As for ducting PVC is a good idea and the insulation is better, if you are going horizontal to get to the gable,I would suggest pitching the pipe slightly toward the vent end, this will prevent any condensation from running back into the fan/light unit.The thru the wall units are O.K., but they let a lot of cold air directly into the room,with the ducted type you are making the hole to the exterior at a point away from the heated area.Another item I suggest is cracking the TOP sash about 1" to let in fresh air to replace the exhausted air.Also, if you are venting vertically without any bends in the duct,it would be advisable to put a 90' elbow on the outside top of the vent to prevent rain and snow from entering the exhaust pipe. regards, GeoffP.S. I've been using a timer on the fan leg for several years now and most customers like them, I do however like the idea of timing both fan and light in some instances,rentals and stubborn parents,:) Geoff
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Bathroom ventilation should be sized for a minimum of 8 air changes per hour. Therefore, with an 8' ceiling, a 50 SF bath would require a 50 CFM fan minimum. If the duct work is long, you would want something with a little more kick, say 70 CFM. Hopefully I'm not blowing alot of hot air...Pun intended!
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I put a Nutone in 10 years ago. Took out the window (horizontal slider), put in a narrower window and filled in with the fun. Fan worked fine, but it was very drafty and the bathroom felt noticeably colder afterwards. If I had it to do over I'd find another option.
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A quick comment re:fan and light sharing a switch. A friend had this in their 2 bath home. I suspect it was a cheaper one as it sounded something between a jet plane and a lawn blower. They had a 2 year old who loved bath time requiring the adult to spend an eternity in the noise or darkness. As luck (previous owner?) would have it, the second bath had a seperate switch but only a shower which had limited appeal to a child.
As to the time required for a complete air change, seems like design of room and location of fan would play a big part. I'm thinking of a paint spray booth where all air is pulled a certain direction for max filtering. Perhaps a fan located near an ajar door would do more to remove/vent air from the outer room then the moisture or odor laden air from the far corner.
*I have use a Nutone in-line fan. More expensive but draws 100 cfm on a 4" duct. Only uses a round vnet in the ceiling. The fan is mounted in the attic space suspended from the rafters. VERY quiet - advantage - people use it because it is not offensive.QUESTION: does anyone have experience with an electronic timer switch that will continue the fan operationf or 15 min. after th lights/fan are turned off?
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Just got back from a vacation in New Zealand. A highly recommended change from an Alaskan winter. We stayed at one place that had a through-the-wall bathroom fan that kept running for 9 minutes after you left the room. Also had powered louvres to close up once done. Went to a NZ home center to investigate. The timer is in the light switch and can be set for 3, 6, 9, 15, or 21 minutes of running after the light is turned off. The powered louvre fan was about NZ$180 (US$100) and wasn't super quiet nor really noisy.
Showers should be vented and illuminated from INSIDE the shower stall where both are more effective.
PVC definitely has the lowest pressure drop.
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Through wall fans work just fine. You can build a painted box around a quiet Nu-tone or Panosonic, mount it at the ceiling wall junction, vent throught he wall, and be on your way in a couple of hours. I leave my Panosonic on for about 12 hours a day, and use it as my whoel house ventilation.
This does have its pros and cons. It cost about $4.84 per year in electricity to run it for 12 hours a day. My humidity level in my house averages around 35%. My house is reasonably tight, about 750CFM 50 on a blower door test. When I have combustion appliances like my woodstove running, The fan and dryer and range hood must be off, and sometimes I crack a window open to get draft. I have a sealed combustion Toyostove for primary heat, so this is not much of a problem. If I had any kind of molds, soil gasses, or other nasties in the vicinity, I would cut in an intake, even though our winter temps get down to -35F. In some nior remodels in this house, I see no sign of moisture problems when I get behind the drywall. Be cautious of too big fans....in a tight house they can cause some pressure problems...Good luck
Scott
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Thanks for the powered louver idea. I had forgot about that idea. Now, a thought. Usually fans fans have no trouble pushing air out, but the problem comes from cold air drifting in. I am currently contemplating venting my kitchen (essentially a complete remodel) and was going to put two 90 degree bends in to increase the friction so air wouldn't blow by the damper. In my experience, they all leak. Thoughts please.
Dennis
*Dennis: Adding a couple of elbows will reduce (but not eliminate) the cold air drifting into a downstairs bathroom. But it will also reduce the air flow going out. Not by as much because the fan provides more pressure to exhaust air than the chimney effect of your house does to suck air in. But what you want is a check-valve. Like those ugly counter-weighted dampers on furnace stacks (to bleed air into the stack). Or those cheap, hinged aluminum louvres on ventilation fans. That's what I liked about those powered louvres. They closed tight when the fan was off and opened to offer very little resistance when the fan was running. They looked fine and didn't project into the room or the outside (each louvre was about 1 cm wide).
*Yes, I know about the dampers. But, they never really close tight and mine seem to leak unless the house has a positive inside pressure. Usually with the combustion from a furnace, there is negative pressure in the house - at least that seems reasonable to me.Dennis
*Bill - You could do this with an industrial relay from Allen - Bradley. I do this alot at work. It would require some slightly different wiring, and the relay would have to mounted inside the fan enclosure, so a rectangular fan might be better. The fan would need to have the power fed to it with a switch leg. I can fax the relay info and a sketch if you like.-Rob
*I frequently use a ceiling fan and send the duct straight thru the sidewall. Use Broan units with an internal damper. Can get to the damper from the inside for cleaning, then there are two dampers - the one on the fan, and the one in the outside wall.DO NOT mount the fan without some type of resilient material in the way - Rubber bushings, hangers, or foam. It is the largest source of sound - direct mounting to the framing. Keep in minf they will get loder as they age due to moist dust readily clinging to the wheel and throwing it out of balance.-Rob
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We have an older home that has a window
in the bathroom. However I'm thinking of
installing a bathroom vent. We're
getting a little staining on the walls
and that seems to tell the tale. Its a
very small bathroom, say 50 square feet
max. Also I'd like to exhaust it through
th side of the gable end of the attic
rather than the roof. Any forseable
problems with that? The bath has both a
bath tub and separate shower stall. Any
suggestions on placement of the vent or
product recommendtions?