Bathroom Fan Ventilation

I have a very noisy fan in the bathroom and wish to replace it. I bought a Panasonic fan but the diameter is 4 inch. The exhaust pipe in the ceiling is 3". Do you know of a good, not too noisy fan with a 3" exhaust?

AL

No. Why not do this the right way? Get up in that attic and install new 4-inch insulated flexible pipe. The job could be over in as little as 20 minutes.

i just replaced my bathroom cieling exhaust fan. problem is that the old sheetmetal duct going up to the roof is 7 inches the new fan has a 4 inch exhuast. is there a problem with going from 4 inches to the 7 inch duct? thanks

There is not a problem if you make the transition from 4 to 7 as close to the roof as possible.

I plan to vent a future basement bath fan through the roof in my south Michigan ranch. I can route it through a section of non-load-bearing 2x6 interior wall with studs already exposed on the main floor -- it has no obstructions in either the basement or attic. I can insulate the outside of the pipes to prevent external condensation, but should I be concerned about condensation inside the pipe running back toward the fan? Would 4" PVC be a good choice for the vertical run, to help reduce condensation?

PVC will not lower the chances of condensation. Insulate the pipe very well!

I have three bathrooms, and in the mornings, when the outside temperature has dropped below freezing, all of the exhaust vents drip water onto the bathroom floors. Our house is six years old. I have my own theories about the cause, but would like to hear an official opinion.

Here is a cautionary tale regarding condensation in a bathroom fan vent line. A previous owner vented my bathroom with flexible, un-insulated tubing, which was draped along the ceiling joists and terminated at a gable vent. The low points in the tubing collected enough condensate to completely fill up last winter. I went up to investigate, expecting a birds nest or something, and found the water. I emptied it into a bucket and poured it out. The next day I came down with what first seemed like a cold, but quickly got worse. The day after that I was in the ER, and spent 5 weeks in the ICU! Turns out I had contracted legionnaire's disease from the standing water in the vent tube. I very nearly died. Moral: Wear a mask when you deal with standing water in attics, and vent your fans properly, with insulation.

I a installing a panasonic bath fan in my upstairs bath,I have a flat roof with fairly little attic space to work with.Their is a 4 inch exhaust duct being used for the downstairs bath fan running up to the roof near my upstairs bath. Is their a problem with tying in my new fan to this existing duct?

Mike,
What do the instructions say to do? I feel you might exhaust air into the other bathroom.

I have a similar problem to micahel. I'm replacing an existing bathroom fan. The house has a (nearly) flat roof and there is only an 8" space between the ceiling and the roof deck. The existing fan vents to a roof vent that is almost directly above the fan (short duct run). We've had condensation problems with the old fan (particularly in winter). When I opened up the ceiling to deinstall the old fan, I found a poorly installed piece of insulated 4" flex tube running from the rigid elbow on the fan outlet through a rectangular hole in the roof deck and terminated in the space inside the roof vent. There is no collar and vent looks like an upside-down 'J'.

I'm not sure of the best approach for trying to remedy the condensation problem. I intend to replace all ducting with 4" rigid tubing (galvanized) and to insulate around it. I'm worried that I'll still be getting condensation inside the vent body and that it will run back into duct and/or fan. Thanks for any advice anyone may have.

JS,
All I can say is to read this column and *all* others I have about this topic and do as I suggest. Surely if I was there we could make it work.

I installed a Panasonic 110 CFM bath fan and piped it to a duraflo roof bathroom fan vent. The result is terrible the Duraflo roof top vent does not flow enough air and the result is my bathroom mirror is all wet. I removed the Duraflo roof top vent and the fan is much quieter and my mirror didn't fog at all! I called Duraflo and they transferred me to the product manager Ken. Ken said that their product is more geared towards the "cheap" $20 fans that don't flow all that much air. He said most of the houses don't have expensive high flowing bath fans.

Does anybody know of a good roof top vent that flows alot of air and where I can purchase one?

Thanks,
Joe

Joe,
What about the company that made my fans? Fantech.

Hello Tim
I have 2 bathrom fans that are venting into the attic..I was told to vent these fans to the outside..I want to vent to the side wall ,next to open gable vents..However the distance from fan to wall is 12 ft. Also I want to drill just one exhaust hole and Y the 2 fans together is this o.k to do..What type of tubing material should be used?
Thank you

Michael,
No wye fitting and go through the roof. Watch my video about Roof Flashing.

I bought a 10yr old 1 story ranch with 2 side by side bathrooms and I discovered on a house inspection that both ceiling fans do NOT vent outisde but into the attic. What is the best way to fix this? Through the roof or throught the soffit? The house inspector I hired before the sale discovered this and reported no mold situation...

Greg,
Simple..... Read my columns about bathroom fans and watch my cool video about Roof Flashings for Bathroom Fans!

My problem is bathroom odor. I have a private potty closet with a 10 ft ceiling and I don't think I get good circulation at the two foot level at the source of the odor.

The commode is scrubbed twice a week. I've installed a battery powered air freshener like you see in fine restaurants and letting in as much sunlight helps but the odor remains.

Flushing removes the odor of the bowel movement but hours later there is a stench that lingers. Its got to be some mold or fungus around the potty seat which I replaced recently with some success, but the smell appears to be building up again.

The fan is combined with the light and I was thinking about separating the two to enhance the fan efficiency.

Mike,
Go read my Sewer Gas Odor column.

I have (2) bathroom fan/light combinations that are not vented. They are in close proximity to each other. If I decide to vent them, can I tie them together and vent them to the soffet as a single output. I would use flexiable tubing.

Jim,
This is usually not a good idea as the air from one can blow back into the other bathroom because of static pressure issues.

I just had a new roof and plywood surface because of rot, roof seems to be leaking but moisture is every were. My fans duct runs out to eve and it is made out of a six foot flex drier duct hose. I have a low pitch roof with rubber surface and no room in attic to work on or even see duct.
What type of exhaust should I have and do you think this could be my moisture problem.

Tanks for any help.

Linn,
You could have multiple things happening. It is possible to vent straight up through a rubber roof. Read all past Indoor Humidity and Condensation columns here at my website.

DEAR TIM:

I have a limited outside wall availability in my bathroom which is on the first floor of a three family home. I need to install an outside vent. There is a flat roof on the section of the bathroom where I could create an outside vent. I have purchased a 4" soffit round vent with an attachment for the 4" duct work. I plan to install the metal ductwork with a right-angle adapter and the fan will be about 3 feet from the soffit. This vent does not have a flapper like a roof vent but there is one in the exhaust fan. Can I exhaust the air downward? Is the flapper on the fan enough?

Thanks
Steve

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Steve,
You can do all of those things. Test it extensively before covering the system with drywall.

can i terminate my exhaust fan at a gable vent?

can i use 4" abs pipe for venting my bath exhaust fan?

I replaced an existing bathroom exhaust fan with a higher powered model. After showering in the bathroom, the exhaust vent is quite wet and actually drips water. I am using 3 feet of flexible tubing from the fan that attaches to non-flex sheet metal duct pipe, exiting straight up to the roof (about 12 feet). How do I reduce/stop the moisture in and around the vent? The temperature outdoors and in the attic is currently about 20 degrees.
........Help! Thanks.

Hal,
You can do whatever you want to do, but I would never do that......... I tell you why in the column above.

Hal,
You can as long as you can create joints that will not leak any water vapor.

Dave,
Did you do everything I said to do in this column?????? Are the exhaust pipes insulated really well???????

For many on low budgets and DIY, cutting into the roof is scary, and wall ducting may be impossible. I share your concerns about a vapor plume that would hover under a down facing soffit vent. Seems a solution is a run that 90 degree angles down through the soffit, and then 90 degree angles straight back out to a termination that is no longer under the roof line. What do you think of this, and would you know of products made for or able to do this? Thanks for the great articles!

Tony,
Watch this to get over the fear of installing a vent flashing:

http://www.askthebuilder.com/Roof_Flashing_for_Bathroom_Fans_Video.shtml

Your idea has merit so long as the two 90-degree bends do not add too much static pressure to the fan. Each 90-degree bend equals 10 feet of straight pipe!

I have a 150 sq.ft. master bath with 9 ft. ceiling. There is a toilet, large shower and large whirlpool tub. I was of the impression that I should have about a 200 cfm capacity exhaust fan. The builder states that the heat loss/heat gain analysis indicates that a 90 cfm fan is sufficient.

Is he correct? To me, there is a LOT of moisture(fan running) after a lengthy shower which can't be good for the LCD over the whirlpool.

Peter,
You need one of the remote fans I talk about in my other Bathroom Fan Column. It is here:

http://www.askthebuilder.com/665_Bathroom_Exhaust_Fans.shtml

You need a setup like I have where there are two inlets sucking the humid air up and out the roof.

I may have ommitted my e-mail address in submitting my question earlier. The question was (is):

I have a 150 sq. ft. master bath with 9 ft. ceilings. There is a toilet; large tiled "rain-forest" shower; and, large whirlpool tub. I understood that not less than a 200 cfm exhaust fan
would be required but the bilder maintains that based upon the heat loss/heat gain analysis, only a 90 cfm fan is necessary. Is he right or should I insist on the larger fan?

Thank you.

Peter,
I answered you. Look at my last response above. Read that other column.

The basement toilet rough-in is located 45 feet from the nearest available outside wall. Can a standard 100CFM exhaust fan work with this length of 4 inch ridgid duct, if not are there any other options?

Dave,
What do the written instructions say that come with the fan??????

I have an older cape built in the 50s, i need to add a bathroom fan due to moisture and mildew building up.
the problem is i dont want to go through the roof, and if i mounth the fan in the ceiling and exhaust out the wall it is at the exact height of the gutters.
do they make a ducting that elbows down inside the wall so i can mount the exhaust lower outside ?
and secondly can you mount the fan directly in the shower ceiling without damage to the unit ?

Robert,
Please read all of my Bathroom Exhaust Fan columns and watch my video where I show you step-by-step how to install the flashing through the roof. Get the fan I show in the column that looks like a flying saucer in my attic.

I'm having a similar problem to Jay. When the outside temperature drops below freezing and then warms up above freezing again, my bathroom exhaust fan drips water. Having read your materials, I'm thinking that the warm, moist air is condensing and freezing, and then melting and dripping inside when it warms up again. Is this the only reasonable explanation?

Neil,
It is the *only* explanation.

Tim,

I just checked the attic ducting for my (2) bathroom fans (back to back baths). Looked like a coiled up rattlesnake lying on the attic floor. What a mess; it was at least pushing out some steam/air. I read your articles about installing a "bathroom exhaust fan termination cap that includes a damper" and understand it to be the best solution. I wanted to know about alternatives.
The questions I have are as follows:
1. Can 2 fans vent and terminate at the same cap/damper? (Using a Y connector).
2. Can they go straight out above them vertically or will condensation run back down into the fans? (I would use foam spray on galvanized steel pipe ducting).
3. Is foam spray on PVC equally acceptable?
4. Could I also run the ducting horizontally across the attic to a gable end of the house and install a vent/cap at that location (5-10 feet) away from the existing attic ventilation "hole"? Would this be an acceptable solution?

What are your thoughts? Catonsville, MD.

The concern about condensation forming inside the pipe and trickling back down, causing the "dripping bath fan syndrome" is a very real concern, and insulating the pipe will do little, if anything, to alleviate this. Cold air from outside enters the duct through the hole in the roof, insulated duct or not. While the duct must be insulated, insulating alone not prevent condensation. Venting it to the soffit is a better plan, creating a negative grade on the duct in the process so that condensation will run towards the outside of the house. Just make sure that the vent hood is installed in the soffit as close to the fascia as possible and as far from the wall as possible. Install non-vented soffit around the bath fan exhaust outlet and seal the outlet to the soffit to avoid the problem of moisture entering the attic through the soffit. The other advantage of venting it to the soffit is that the insulated duct will also be buried in the attic insulation and will be kept entirely on the warm side of the insulation. Make sure that all duct work connections are very well sealed and that the bath fan housing has a vapour barrier installed around it and that any holes/tears in the barrier for wiring and ducting are well sealed. Covering the whole unit with a mass of spray foam is the best approach.

Greg,
Whoa partner!!!!!! I very well may delete your comment as it is questionable advice. I find it troubling for these reasons:
1. There is warm air from the room floating up into the pipe all of the time. Some dampers leak more warm air than others. Granted, the vent pipe will not be room temperature, but within seconds of fan operation it will be.

2. Dumping hundreds of cubic feet of moist air under a soffit is BAD advice. Why? Much of that air can be drawn into an attic space through continuous soffit vents. This moisture can condense on the cold roof sheathing and roof framing.

3. Spraying foam on an appliance that might have a heat lamp or regular bulb might cause an electrical fire. You have to create air spaces around some fixtures to dissipate heat.

Dude, you have to be very careful about making universal statements........... There are always secondary reactions to primary ones. You need to think through always what are the secondary reactions.

Hi Tim,

We want to install an exhaust fan in our master bathroom. The ceiling is vaulted and I'm wondering the best approach to insulate the pipe since there is not much, if any, space to work in. Based upon your advice, I believe venting to the roof is the best option and not the soffit.

Thanks,
Kim

Kim,
I would think seriously about building a dropped soffit in the bathroom to house one of the remote fans that I use. Then you would have the needed room to make all of the connections and pop out the roof.

In your article you say you prefer smooth galvanized duct. My bathroom fans have horizontal outlets, which means that to vent through the roof they will need a 90-degree elbow fitting. Is this still better than using insulated flex duct, where I can make the turn more gradually?

Any tips for venting first-floor bathroom fans? My house has 2x6 joist framing and no crawl space between the first and second floors. I have a half-bathroom on this floor that is in the interior of the house - no exterior walls. Our plans are to eventually add a shower to this bathroom.

During a renovation of the adjacent kitchen area, we discovered that this bathroom's existing exhaust fan was connected to a duct terminating in the ceiling space at the back of the house! (Good thing this is only a half-bath!) Presumably the fan used to vent out the back, but when the previous homeowner built an addition onto the back of the house, they simply cut off the vent and left it in the ceiling.

The kitchen contractor upgraded the fan (in anticipation of the shower) and installed a new vent. It is 4" aluminum flex duct that goes horizontally through the ceiling to one of the bathroom walls, makes a 90-degree turn downward through the wall into the basement, then another 90-degree turn to continue through the basement joist space, exiting the house through the exterior wall just above the foundation, terminating with a vent cap.

I estimate that this duct is about 18-20 feet in length.

There must be a better way. Any ideas?

Jason,
Sorry, I would have to be there to see all the possibilities.

Okay - let me simplify. What's your preferred method of venting a first floor bathroom in a two-floor house?

I am remodeling a 1st floor bathroom and need to make some changes to the exhaust fan setup. Previous owners had drop ceiling and the exhaust fan ran 3-4 feet to the outside side wall. Going outside is the only option as directly above on the next floor is another bathroom and on the third floor is a bedroom.

I am going to get a new fan and tube, but as I am raising the ceiling above where the drop ceiling was, I need to run the tube through some of the ceiling beams. Can I do that or is that a problem as they are load bearing?

Jon,
You may be able to bore through the beams so long as you stay in the center and the joists are no less than 2 x 12s.

Jason,
Get a building code book.

Jason,
Through the closest wall.

In regards to tying in 2 fans into one vent; don't do it. I had tried to be "efficient" by tying a downstairs, and upstairs clothes dryer into one larger vent pipe. When one dryer ran, condensation, and dryer smells would occur at the other dryer. I installed baffles at the each dryer and used a screened open outside vent to eliminate back-pressure in the pipe. Still did not solve the issue. In the end, I did it properly with 2 pipes, and no more problems.

My house is 50 years old and there has never been a vent fan in the bathroom. I am now having the bathroom wallpaper stripped and repainting the walls and ceiling. Should I consider having a vent fan installed? There is a lot of moisture and condensation after showering. The house does not have an attic. What expense should I expect?

can you install an exhaust fan directly above the shower.

I have a 1 foot thick structural Insulated Panel (SIP) roof with metal locking shingles. This is all on top of the roof trusses causing my attic space to be completely insulated and heated. I don't want to perforate the roof for this reason and would like to vent my three bathrooms out the side wall. Can I connect them together in a manifold with individual dampers from each bathroom? Should I angle the exhaust pipe exiting through the wall downward so condensation drains outside? Thanks

Can I vent the bathroom exhaust fan to the same outside vent that the cothes gas dryer is vented to using a metal "T" connector.

A sibling just purchased an older log cabin with two bathrooms,with showers, in need of ventilation. The ceilings are actually the roof deck and are angled up from the outside wall to the ridge log. The roof line overhangs the outside wall by 1' without facia or soffit. What do you suggest for ventilating these rooms? They share an inside wall.

I am installing a bath fan in an inside bathroom (middle floor not near outside or roof). Can I connect the new ducting to another existing bath fan ducting that is located only 6 feet away?

There's a roof vent kit marketed by Broan that uses 2-ply metallic laminate flexible duct (okay, okay, corrugated plastic hose) instead of the solid pipe you show which you insulate afterwards. I live in SC where the temps between summer and winter hit both extremes. This platic hose seems like it isn't up to the task and I need to fix the previous owners sloppy work FAST. (the bath vent has hose laying near the overhang in the attic. yup, just laying in the attic) You're the pro here. You tell me what I need to do. Thanks.

Hi. I just had an exhaust fan installed in my only bathroom and vented it through the roof. They did a poor job overall. I like the idea of spray foam, do you have to also coat the metal box enclosing the fan and motor? There is no insulation anywhere around the box. Secondly, there are several holes in the metal box and when the fan is turned on, a lot of air comes through these holes rather than go up the vent pipe. Can or should all these holes be covered? Thanks.

Tim,

I wish to put in a high-end fan, one with added light and heat lamp, prob. about 110 cfm. Panasonic was the most popular in CA where we previously lived because they were touted as quiet and I think CA code required fluorescent.

We're no longer in CA and I remember the nice feel of the traditional "red" glow from the heat lamp and I've always detested fluorescent lights. Can I still use incandescent lighting with a red heat lamp bulb and still get a quiet fan? (I've noticed some makers have halogen lights with intensity variation control but have not found any heat lamp bulbs.) Is this totally out of vogue and impractical for some reason? What are other popular high-end brands?

steve

Looking for a bathroom exhaust fan that is very strong and maintenance free. Which brand have you seen good luck with?

Can I exhaust my bath fan to the soffit if I cut a hole in the soffit and mount the pipe

We bought a house with a roof vent for the bathroom fan. It has a flexible hose running from the fan to the attic (I know it needs to be insulated, but that is not my main problem). We can often get a snow buildup of 2 feet on the roof, which completely buries the vent, making the fan useless. Is there a standard way to extend the vent above the roof a couple of feet to avoid this, or do we have to rig up an invention? Or, although I know you recommend against soffit venting, is this a scenario in which that would be preferable, if we were to seal up the soffit for several feet on either side of the vent in order to prevent re-entry of moisture into the attic? Thanks.

Tim,

I'm installing a new exhaust fan in a first floor bathroom of a tall two story house. Would it be acceptable to run the vent out through the side wall if terminates about 8' below the soffit? I know you recommend going through the roof, but my exhaust ducting would be about 15' long to get it up and out the roof, versus 2' long to go out the wall. Would a 2' section of solid metal pipe run horizontal out the wall insulated with foam be the best solution?

Thanks.

We live in the Atlanta region. Our 30 year old home does not have a bathroom exhaust fan. We have a window in the shower and a light above the shower. After reading the referenced information, we feel it would be best to have a professional install a fan. Do we call an electrician and a roofer? By the way, thank you for the warning about exhausting into the attic. We were told that it was okay to exhaust the fan into the attic because "we live in the south".

Tim,

I share your concern about moist air not terminating in a soffit. My bathroom fan is currently terminated through a side wall about 3 feet under the soffit. I would rather not change this to exhaust through the roof on the front of the house. Your thoughts?

I am adding an exhaust fan to my new bathroom & am curious if I can vent the fan using the exhisting 4inch waste water vent. The roof is metal.

What type of service person is the best to call to install a bathroom fan to the vent to the roof? There is no previous fan in the bathroom. There also is no room in the attic for a service person. Can it be installed without access to the attic?

I have a fan vented from my bathroom ceiling through the attic and to an outdoor side wall in the attic (about 5 feet of plastic tubing). This works fine. I have no leaks. However, i am getting some mold on the bathroom walls in the winter in my bathroom. This does not occur in the spring, summer, or fall. Do i need to insulate the tubing in the attic (it is not currently)? or is there some other issue i am missing? Thanks.

steve

What do you suggest for a metal roof?
I'm installing a metal roof and replacing the upstairs bathroom vent duct with a steel pipe. Currently it is an uninsulated flexible pipe.
I have the same square vent as shown in your blog. How do I flash it into the metal roof?

My bathroom exhaust fan is vented through the attic and out thru the outside soffit. I have a problem in that the painted area of the soffit surounding the exhaust outlet is now peeling. I just painted the area a year ago and installed the vent at that time also. I will prime and repaint this area of the soffit, but am almost certain it will peel again by this time next year. I would vent thru the roof, but would rather wait until the roof is replaced in a few years. How do I keep the exiting moisture from peeling the surrounding paint? Thanks for any advice.

We have a 2nd floor bathroom with no attic space, and no exhaust fan was put in when the house was built about 25 years ago nor is there any ceiling lighting. The mold/mildew problem has gotten so bad that I thinking of gutting the bathroom. Is there any certain type of fan that we should use since it will have to be wired and will vent directly to a steep pitched roof?

I read your article cautioning about venting a bathroom fan ito the attic. In looking at my home it apppears that the original builder did exactly that.
None of the roofers or attic insulators who have worked on my home over the years even mentioned a mold problem. Does the fact that I've had vents installed in both side gables and along the roof ridge help alleviate the problems your mention about mold issues caused by improper bath fan venting?

We recently had a fan installed, the installer vented the exhaust to soffit. However he said he could not make the connection to the outside damper valve. So, he left it exhausting into the soffit. What do I need to do or is this acceptable?

I recently purchased a 30 year old house. Both bathroom exhaust fans are non-functional and need to be replaced. In scoping out the work, I went into the attic and found that neither fan is connected to an external exhaust vent, something that will need to be corrected. Unfortunately, the house doesn't allow me to easily vent to either of the end soffits as they are made of cinderblock. I can cut through the roof and install vents, but each bathroom already appears to have a PVC pipe vent for the plumbing. Can I "tie into" the existing vent using a Y or T type connector and then attach the exhaust fan hose to that? It would prevent me from having to alter the roof.

I have several 4-inch diameter bathroom exhaust vent pipes that end in plastic vents mounted underneath vinyl siding. These vents each have four rectangular plastic flappers, all of which have worn and fallen off within the past eight years. The flaps look simple enough, and surely the manufacturer would have replacements available, but the manufacturer doesn't seem to be named on the units. The building supply company folk say they can't order new flaps, that I should buy whole new vents, take the flappers from them to replace the missing flaps. Is there a source of replacement flaps? And is there a better solution? removing the vents would require removing all of the siding above the vents.

Hello,
I am trying to install a replacement fan in my master bathroom. The builder-grade fan that is currently is only 50 CFM and the room size is approximately 120 square feet. The current ductwork is only 3 inches and the fan requires 4 inches. Can I put replace the section of ductwork up to near the roof, and then use a 4 inch to 3 inch adapter near the exhaust termination cap. That way I will not have to mess with the roof and shingles, correct? If yes, where would I be able to find that 4 inch to 3 inch adapter...a big-box home improvement center, HVAC or plumbing supply house, etc.? Thank you!!

Great video, but I'm not sure why you trimmed the shingles to match the square frame of the bathroom fan vent. Wouldn't it have slid up, underneath, the shingles even if you didn't trim them?

I live in a 50's cape cod with a bathroom vent in the upstairs bathroom. I don't know how long the fan's been there but it's vented into the attic. The attic is pretty well-ventilated and I think that's how I've avoided real issues so far but it's bugging me and I want to fix this. I'm nervous about getting a leak, though.

I watched the video on installing the flashing and I went out a bought the stuff I need. The vent cap says (similar to your video) to cut the hole a bit larger than the ductwork and leave 3/4 on and inch sticking out, parallel to the roof pitch.

Here's where I'm stuck: the vent cap just has a big square hole underneath. So if I stick the ductwork loosely into this and have a gap around the duct, how do I know the warm moist air will push the damper open and go outside? What's to stop it from just flowing back into the attic around the ductwork?

thanks,

-Matt

I have exhaust fans in both bathrooms and in the main part of my home. I get a coniderable amount of clatter from all of them during windy weather. Is this normal or should I have them checked for proper installation?

I am installing a 2 new bathroom exhaust fans. Can the 4" conn on the fans be reduced to a 3" duct without any issues? Can the duct ducts be run into 1 so I only have to cut 1 hole in the side of the house? Also is there a maximum horizontal run for the duct? I am looking to go about 9 feet.

I have a "spare" 4" PVC pipe running from my basement to the roof (3 floors up). This was originally installed by the builder in case Radon remediation was needed, but since the tests showed no Radon, the pipe was never used. We're putting a half bath in the basement (toilet and sink only) and were wondering if I can use this pipe for the vent exhaust. Is there a maximum run from vent to building exit? The bathroom itself is only about 4' x 6', so I was looking at a 50 cfm vent. Thoughts?

Good article. Just discovered during some bathroom renovations, that the fans in my 2 bathrooms exhaust into the attic. I plan to follow the advice in this article. My one question: The one fan is currently very near the edge of the house/roof - what's the minimum distance from the bottom of the roof that I can install the cap?

Previous owner had bath fan venting directly into attic so I installed a roof vent and connected it to my bath fan via flexible ducting. I felt pretty good after finishing this project until I noticed water (condensation) dripping back through the fan. Per the suggestions above, I re-ran the ducting using 4" galvanized ducting with (2) adjustable elbows, one at about 80 degrees the other at about 10 degrees between the fan the roof cap. The total length of the run is about 3.5 feet max. I insulated the duct with spray foam as instructed. Unfortunately, I still have condensation coming back into the bathroom. I suspect that condensation is collecting on the flapper in the roof cap and then dripping back down the duct, but I'm not positive of this. When I replaced the flexible duct, I noticed a lot of condensation on the flapper. The roof cap that is in the roof now is from a cheap kit that I bought at Home Depot. Is there a particular roof cap that works better than any other? This is getting frustrating. Thanks!

I just bought a new fan for my half bath. Once I cut out the ceiling to install and connected to the exhaust hose. It is one of the cheap builders special hose. Now this fan is really only used for stink, since it is a half bath. Now when I connect it to the hose it makes the fan louder than when it is not connected. This fan blows out into the floor joists. I have noway to run a new hose at this point.
Would I really need to connect it to the hose?
Any suggestions?

I want to replace my bath fan. I bought a fan with a four inch exhaust. I plan to adapt it to my existing three inch flex duct pipe, which is in an area that is too difficult to replace with four inch pipe. Is there anything wrong with adapting a four inch fan exhaust to a three inch duct pipe? Thanks!

Great info on all the posts! We are in the process of gutting a 6 X 9 bath with an adjoining wet wall to the kitchen. I have always installed direct powered vent fans, but now after some research, I see the "inline" power units rated for multiple rooms. My question is, have you installed this type of unit yet, and if so, any preferences developed? How about pros and cons of direct powered vs. multi vent, single inline units. Any feedback would be greatly appreciated!

I thought i did everything right.Used the unsulated 4" flexible vent and out the end wall 6 feet instead of the soffit. I insulated everything well. i'm now getting icicles coming down the exterior wall...I don't get it. where is it coming from? Everything is sealed. Did I insulate too much? Ken

Hello,
I thought it might be helpful to review the ASHRAE & Green Building Standards from Panasonic Vent Fans at http://www.panasonic.com/business/building-products/ventilation-systems/ind ex.asp

Good Luck!

I would like to know if I can install a bathroom fan on the bathrom wall rather than the ceiling. I have a brick roofing and trying to avoid having to bore a hole thru the brick.

I saw the article on the bathroom fan, and I'm wondering about the spray foam insulation in an aerosol can. I've searched high and low, but everybody wants to sell me 'Great Stuff' and the like. What is the product that you used, and where can I get some?

Hi Tim,
Interesting material. I live in Canada; cold country. This summer a contractor installed a ceiling fan in my bathroom; the exhaust 4 in dia steel exhaust line runs 15 ft to the side of my house and exhausts via a damper to the outside . The exhause run is linear
and I've noted some light water stains on the ceiling around the fan. Noted the line was "not" insulated. Contractor claims he forgot to install the insulation sleeve around the steel line. Nice condenser in my ceilng!! from the showers. My question; will the insulation definitly aid in transfering the warm moist air to the outside; or do you foresee furthur problems as the line might me long..it was run along the attic above the insulation rather than cut a hole in my roof..Would a shorter roof run , if it is vertical, run water directly backwards to the fan and on the floor. I hope the current line when insulated will correct the problem
thanks Andy

I've installed an inline in my attic. It's a 250 cfm bath fan with 6" ductin. The fan is in the cold air space above the bathroom. There is a damper in the roof vent and also a good one (spring loaded with a rubber ring)at the celing so warm air shouldn't travel up the pipe unless the fan is on. The pipe is insulated with pipe sleve insulation all but the fan itself. In cold weather i still get concentrate coming from the celing vent cover.

I am experiencing moisture problems in my attic. I was investigating and found some wet spots near the bathroom exhaust fan (on cold days fan drips condensate onto bathroom floor). I replaced the existing 4-inch plastic flexible tubing with a flexible aluminum tubing and made sure the connections at the fan and roof were tight. Is the flexible aluminum tubing appropriate for this application? If not, what would you recommend? Thank you.

What kind (brand) of spray foam are you using? That isn't great stuff is it? It seems like great stuff would be hard to apply to a surface.

I have two concerns , one is my bathroom fan ...we took it down to clean it and found out it is not vented outside the space is only about a foot or so high there appears to be a cut out covered over roofside where possibly a pipe was attached is this legal i am renting ,should the housing provider do something ? and do they have too?..second problem i get condensation on the pipe leading down to the main drain enough to make the walls wet right from the top ceiling to the basement wall , these problems are a concern to me since my youngest daughter is highly allergic to all mold types again dose my housing provider have to address these and if they dont what can i do ...the second issue i have asked them to fix but they brush me off saying it must only be from the cold as too it only happends when it is really cold and wet outside i felt it was not insulated but they assure me it is .

i am drywalling the ceiling of a new house and it is -30 degrees out we were heating with a propane heater but the polly all frosted up.i have been sweeping the polly of but am not sure how much moister drywall can take.

Should the fan casing be insulated as well or is that a fire hazard? I just have a fan........no light. Thank you.

We have just installed a shower in our upstairs bathroom and vented through the attic to the outside wall. Our problem is now that we have a major cold spell, it is not venting. We think the flap outside is frozen and therefore the air is not venting out. For now we are just waiting for a warm up to see if this is the problem. What can we do to prevent this from happening again during future freeze ups.

Do you have instruction on how to install bathroom fan in mid-level?

Regarding bathroom exhaust fans mounting into the second floor ceiling with the metal fan top(and exhaust outlet exposed in the attic).
Why is Mr. Tim Carter only suggesting exhausting bathroom fan exhaust to the roof and he gives no comment about exhausting using rigid or flexible 4inch insultated metal pipe to a standard plastic vent (with a one way vent flap) mounted outside on the side of the attic wall which often is a shorter exhaust pipe run than to the roof? Also it does not require working on the roof. I am not discussing exhausting through a soffit but exhausting through the wall by drilling a separate 4" hole while workig from the attic and then installing a plastic Vent on the outside.

I want to install a bathroom vent fan in a large shower/bath/vanity area that is connected to an existing toilet area vent fan. Is it a problem to add a T connecter to accomplish this?
Thanks,
kg

My home is 45 years old. I am installing a new fan in one of my bathrooms. I have 3 bathroooms all together. The ducting (galvanized) from all of the bathroom fans connect into a collector box and then go into a single duct that exits the roof.

All of the current ducting is 3 inches. The new fan has a 4 inch duct connection. I was planning on using a 4 inch to 3 inch converter so I can hook into the existing ducting. Should I put the converter after the fan and run new 3 inch ducting to the above box, or should I run 4 inch ducting from the fan to the collector box and then convert it to 3 inches. The distance is about 6 feet.

I was worried if I did the 4 inch to 3 inch converter further from the fan I may have more condensation.

Thanks for any help !

Chris

I read some of the comments about the bathroom vents. So here is my issue. My fan is a nutone model, it a coned shaped fan that mounts in the attic. My fan freezes up when it gets cold, so i went up and looked and the pipes were not insulated. So i took it apart and found almost a gallon of water and ice in the intake pipe. So like i said i took everthing apart and sealed everything back up and insulated the pipes. But to find out that it still freezes up and iam getting water in the pipes. So then i thought maybe i didn't have a vent flat and that was letting moisture in, but i do. What would help this, cause even my insulation is wet. I do know the wife doesn't run the fan very long, she shuts it off right after a steamy shower. Would it help to run it for alteast 15-30 min after a shower to get rid of that moist air thats in the pipes or what. Iam stumped, cause i did everthing up to code but nothing seems to help very good. Thanks

I live in high Southern Arizona, hot dry summers, a month or so of high humidity, then temperate dry winters. One bathroom has a plastic vent that ends near the roof, not insulated. The other is more substantial, but again, not insulated. Do you recommend replacing the plastic vent tube (much like a plastic dryer vent), extending it up to the roof fitting, and then insulating it? I don't really see the value of insulating the vent tube. Is there such a thing as a timer on the vent switch? The kids leave it on and I'm venting conditioned air out of the house and I'd like to minimize the air loss.

I want to install a ceiling exhaust fan/light in the 1st floor bathroom of a 2-story house. There is no existing fan nor ceiling light fixture. I can run the wiring via the crawl space below the bathroom; but I cannot figure out how to vent the fan to the outside. What do you suggest?

I want to install a bathroom exhaust fan in each of two bathrooms located on the 2nd floor below the attic. And I want to exhaust the air through one common roof vent. How do I isolate the two fans from each other?

its always windy...........
the wind blows open my bathroom
exhaust fan's flapper/damper.
its driving me crazy.
can i add some kind of wind deflector in fron of the flapper opening?

Mr. Builder,
The video on how to install a bathroom fan was very informative however, how would you duct when installing on a flat roof? I believe that its based with tar or sholuld this be avoided with a flat roof?

Can you tell me how a bathroom vent fan with a heater works? Wouldn't the heated air be vented out and defeating the purpose of the heater feature?

To vent the exhaust straight up to the roof will require a duct pipe approx 8 ft long. The outside wall of the house is only 3 ft away. Would it be better to put a bend in the pipe and vent it via the outside wall, or go with the longer pipe straight to the roof?

I have a 4'x 8' area with the shower taking up half the area and toilet in the other half. Is it better to install the exhaust fan in the 4x4 shower area or in the area of the toilet just outside of the shower area?

Hi, In 2005 we had our 3 vents (2 bath and 1 kitchen) connected to pass out the roof when our mid-Michigan ranch style house was reroofed. Previously they exhausted in to the attic and had rotted the roof plywood. New roof caps with flappers were bought and installed. That winter all 3 connected vents produced condensate that leaked in to the house. In 2006 extra insulation was put on all the ductwork. The condensate leaks continued.

In 2008 we hired a different contractor to fix the problem and to install new fans. We asked that PVC tubing be used (watertight) and that the vent pipes be passed through the soffit. The job was stopped halfway as it was found that both the electric work and new ductwork need to be installed and inspected per state code. This could not be arranged before snowfall and remains to be completed.

Now we're having second thoughts about moisture coming back in to the attic through the soffit. We've requested that 2' of solid soffit be placed on each side of the vent exhausts (required by code) but this will probably not be adequate as our soffit is totally perforated.

Our questions:

The worker who installed the bathroom fans and ductwork last fall said there was an electric wire between one bathroom fan and soffit so he had to put an elbow in to the PVC pipe to get over the wire. Should this be allowed?

Shouldn't a building contractor be able to insulate a pipe that passes through the roof so no condensate forms to drip back in to the house?

Thank you.

I'm thinking about buying a newly built ICF home, & the builder has installed bathroom vent fans in the wall & ceiling. Is this correct?

Wall mounted vent fan under toilet tank & above baseboard in all bathrooms. Fan turns on when ceiling light closet to toilet is turned on. Hose vented outside thru wall. 80 CFM.

Second, ceiling vent fan in larger bathrooms when ceiling light closest to shower stall & tub is turned on. Hose vented thru roof. 80 CFM.

One half bath has a fan under the toilet tank & the hose runs up the wall to the roof, about 15 feet straight up, is this correct? 80 CFM.

Should I pass this house up, or is it ok to have bathroom fans like this? 8 in wall, 4 in ceiling. Some bathrooms will have 180 CFM, is this ok?

I have a bathroom exhaust vent that gets rain into the vent under certain heavy rain/wind situations, causing water to come into the bathroom. It only happens a couple times a year, but it is not a Good Thing. I had a roofer check the flashing and seal everything very well, so its not coming in there. There is a damper, but we can hear it flapping when the wind is strong and gusty. The cap is rather short, mushroom shaped. I suspect the wind has to be a certain strength and direction and the rain splash from the roof large enough volume for this to occur.

I am having my roof re-done due to recent hail damage. I want the roofer to address this problem and solve it once-and-for-all at that time. Can a taller cap help? How about a different design?

Our bathroom vent is on a sloped area of our roof running towards the valley. The vent is on the upper half of the roof and runs to the lower half. This winter we had a lot of ice build up and needless to say we had water come into our home. Is there any type of extention that we can put onto this pipe that we can have it up over the snow. We do live in a snow area and have had troubles other years.

Tim:

There was a recent letter from Keith(?) on this topic that had not been answered. I can’t find it again, but it was about intermittent water coming though the ceiling exhaust fan in the bathroom, with all indications that the roof termination vent was installed correctly. I also have this problem in two bathrooms and after investigation it appears to be caused by the 10X12 roof pitch. The flappers on the roof termination vents are being held open by their own weight due to the pitch of the roof, meaning that the flapper is actually open in the rest position. When the wind blows, the flapper is closing it against the frame making a loud “tapping” noise and in high winds with rain the water readily gets in. The problem is neither my builder, or I, have had any success finding a roof termination vent for a 10X12 roof. I can’t find anything that does not have a flapper, like an Attic Vent or Gravity Vent that the manufacturer says will work. The builder wants to run the fan exhaust up to the ridge vent and I know that is just going to be a mold problem. Can you direct me to a source for a roof termination vent for a 10X12 roof?

Thanks!

Hello,

I installed a larger bathroom exhaust fan than needed but it still does not ventilate the steam from the shower.

Besides the piping being blocked or the damper being stuck, what could be causing this?

THanks,

Jason

i would like to know if there is a problem with my bath fan? I went and replace the bath fan with a kit and found that there is no ducts just a conceal vent box. It that normal with some home or is was installed inproperly from the old owner. And if so do i need to do something about it or just leave is alone?

We had an electrician install an exhaust fan in our very mildewy bathroom. At the time, I didn't know better, so I let him vent the fan with flexible uninsulated ducting through the attic and aimed at a side attic vent.

Now reading your column, I am very concerned about this method and want the duct to be vented through the roof properly, as you suggest. I'm not handy enough to do this myself. Who would I have to call: a roofer or another electrician?

I apologize for my amateur question, but I am really concerned, especially since the exhaust fan didn't end up being powerful enough to diminish the mildew and we'll probably have to move the exhaust intake closer to the shower stall... I only wish I had found/read your columns sooner. Thank you!

I recently purchased a renovated home. However, one of the bathroom exhaust fans makes this eerie knocking sound. Do you know what would cause that and what I can do to fix it? Much appreciated!

I'm planning to install a bathroom fan and was wondering about other vent options. Will it be a problem to install a wall vent from inside the attic through the side of the house? I'm guessing that you will not recommend that because the duct will be horizontal and possibly sag over time and cause pooling as another writer stated. Also, being in the snowy Northeast, wouldn't a roof vent get covered with snow during the winter?

I just made a brand new bathroom adjacent to a big walk in closet, what do you advise in order for the humidity not to go into the walk in closet. Our Contractor has done nothing.He was also the architect of the project. Please Help

Dear Tim,
I have three bathroom exhaust vents are installed at the soffit. I have complaint these to the builder on my Year-End report to Tarion for violation of the 2006 Ontario Build Code, Div. B Part 6, 6.2.3.8 (4 & 5). But the builder inspector said these vents at soffit are all right and the Part 6 of 2006 OBC is not applied for free-hold-town-homes and is only for commercial buildings. Is this true? Please let me know why…

It seems to me that everyone knows, except the builder and Tarion, bathroom exhaust vents being installed at the soffit is a bad practical, why the builder is still installing vents at soffit???

Thanks in advance
Andrew

I have two bathrooms that are back to back and that need new fans . Do I need to cut two holes in the roof for venting , or can I connect the two and vent out with one hole ? I live in Mass..
Thank you ,
John

I have a 25 year old home. i will be replacing my bathroom/shower vent very soon. along the floor along side the toilett is what appears to be a vent. bugs enter the home through this. id like to seal it up but do i need it?

My bathroom ventilation fan was noisy before, but now stop working, what can I do? This is about 10 years old townhouse. If I need help, who do I have to phone?

Thank you

I was thinking of doing this as well, running three exhaust in one... if it was tied in as close to the roof as possible with at least a 45 degree angle would it still psh air back into the other bathrooms?

I am installing an panasonic FV05VF@ in a bathroom that was a complete gut. I

The fan is mounted on a joist. Do I drywall up to the edge of the fan or do I cover the flange with drywall (cover screw holes)

marc

Dear Tim:

Your argument for NOT venting a bathroom fan under the soffit is convincing. I would appreciate your opinion on a "hybrid" approach before I delve into the project.

The duct would run straight from the fan housing, horizontally, in direction of exterior wall, resting on top of the ceiling drywall. In just a few feet, over the exterior wall, the duct meets the underside of the roof, sloping downward. Right there I would mount the roof vent cap, and make the connection with a duct elbow, adjusting its angle to match the slope of the roof. Do you see any problems with this approach?

Advantages:
(1) The 3-inch vent duct is nestled in the loose insulation between the 2X4 attic joists, and covered with additional batt insulation I intend to add above. No other insulation of the duct itself is needed to prevent condensation in the duct.
(2) It is about the shortest route for duct work that I could possibly choose, with only a single, slightly angled bend.
(3) Most if not all of the installation work can be done from within the bathroom or outside on the roof, reaching through the access hole for the fan housing in the bathroom to put the duct in place. Little or no crawling in that very cramped corner of the attic would be necessary. On my split-level house I would have the advantage of standing on the lower roof level to work near the edge of the roof where the vent cap would go.

Do they make a 200 cfm with a light and heat?
Thanks
Lisa

How much fan do I need to vent a single 5' x 9' bathroom, used by 4 teenagers?

Is there a distance from the bottom of the roof that the roof vent should be. Example at least so many feet from top or bottom of roof

Hi,

Our current bathroom exhaust fan is a 50 CFM and we would like to change it out for one with more CFM. Our problem is we currently have a 3" roof cap to match the 3 " port on the existing fan and the new fan would have at least a 4" exhaust port.

Any suggestions around this without pulling shingles off our fairly new roof and installing a bigger roof cap?

Thanks
Bob

I plan to install a basement bathroom exhaust fan and want to know if I exhaust at ground level about 2 feet from a window. The wall near it is an exterior wall and filled with insulation. So I am finding it difficult take it up any higher with a 4 inch flex cable.

hey ATB....I have a townhouse and the bathroom fan doesn't outlet outside, but rather into the attic...which is another problem with the homeowners association. Other then that my fan typically only lasts for 3-4 months and then gets very loud which I'm assuming it's toast at that point. I have replaced the switch, any telling what else could be damaging these fans...their getting pretty expensive.

What if I have a bathroom exhaust vent that is never used but serves as a water spout over the master bathroom toilet during severe rain storms. Since we do not use the vent, I thought I might want to seal the external vent. Is there a proper way to do that?

Thanks!

Mike.

I just moved into a 2 year old house and in each bathroom of the house I can hear what sounds like water dripping on the vent. I am new to home ownership and don't know what to inspect or what to look at. Any ideas on how to fix this?

Tim,

I insulated my exhaust duct with thin adhesive foil-backed foam. After reading this, I'm guessing that's insufficient. I've looked at all of the local hardware stores and home centers, but haven't been able to find spray insulation for an application like this. I've only found stuff to fill gaps and cracks. Where can I buy the foam you recommend in this article? Thanks!

When venting a bathroom fan is it necessary to cut another hole in the roof or if you have existing vents could you just hang the vent slightly below those?

I have two new recently installed panasonic fans in 2nd flr baths - both properly done with insulated ducts and roof outlets. I am beefing up insulation in the attic. Can I put insulation on top of the fan housings in the attic? faced/unfaced? foam pieces? Since the housings 'protrude' I was thinking I would cut small pieces of insulation or foam to place on top of them to eliminate a few more voids in insulation up there.

I have a problem with water dripping out of my fan as well. I have already replaced the steel stovepipe that was originally used with a pre-insulated flexible duct recommended by my local hardware store but it still drips. Any other suggestions.

I have a home constructed in 2005. It is energy star certified. I've had leaking bathroom fans ever since I installed a whole house humidifer. I turned the humidifer off three days ago, but they are still leaking. All of the duct work is insulated. Any other ideas?

Tim,
I'm installing a bathroom basement and the only way I can run an exhaust pipe for the fan takes me out the house right under my deck. Is there a problem with continuing the run of the pipe under the deck so I don't exhaust right under the deck (I'm assuming that's not a good idea).

Is it acceptable to ventilate two different bathroom fans into one exhaust duct and vent?

i would like to put an exhaust fan in my basement bathroom but there is not enough room in the cieling to put the fan. can i mount an exhaust fan in the wall? or do they make wall exhaust fans?

I am up in Canada and I installed a more powerful and less noisy bathroom fan last summer. I used a 6" PVC spiral tube with an insulation sleeve that goes from the fan outlet to the flashing up on the roof. I noticed my ceiling around the fan was leaking water. I went back into the attic and nothing is leaking from the roof... I noticed however, ice forming on my fan box, which is not insulated (just wrapped with vapor barrier to keep the moisture from escaping into the attic). I am thinking that that is the ice that is melting and leaking on my ceiling. The previous fan was not insulated and we didn't have any problems with condensation (it just wasn't powerful enough and was very noisy). Do you have any tips to stop ice forming around the fan box? ...or do you not think this is the problem.

Thanks!

In late October I used a contrator to install a bathroom exhaust fan. He vented it to the attic. Here it is the end of December and I now have mold in my attic. Is tht standard for a contractor to vent to the attic? I feel he should be held accountable for the mold treatment. I have been told by Pest control comapnies tht he should have vented it to the outside?

This may be of interest. When I built my upstairs bathroom from scratch. I thought about the problem of venting steam. I was very delighted with the results. The bathroom was built in a bonus room above the garage that was shaped like a barn. When building the walls to the original "slanted" wall, I left the top area open under the lower roof beam (4"x 7" triangle hole) on each side leading into the main room. Then installed a fan that actually sucks. (100 cmf or more, I forgot.)vented thru the roof. (3ft, 4in duct). Used for well over a year with no, I repeat, no steam at all. You can feel the air being sucked into the room thru the top holes and under the door. There's no moisture on the shower ceiling either. How do you like them apples?. Result, one very dry bathroom.

Jeff

As a roofer for 38 years, self-employed for the last 25 years, I've seen this problem twice. It's the exact problem George describes. I've dumped up to 3 gallons of water out of a flex pipe draped across ceiling joist. Always vent pipe through the roof if possible and run the fan for 10 to 20 minutes after getting out of the shower to help dry out the inside of the pipe.

I've read all of the bathroom fan posts, and none are like mine. So here goes:
I put a full dormer across the back of my house 10yrs ago. Prior to then, I had vented the 1st floor bathroom fan thru the roof as you have described. After the addition, the 1st floor bathroom fan vents thru the N wall to the outside; so far no problem there.

BUT, the 2nd floor bathroom ventilator also vents thru the attic to the soffit, using uninsulated flexible ducting. Works FINE most of the time, UNTIL we have a high wind + rain storm.

We also installed a ridge vent running the length of the main roof, at the same time as the addition. When we have the high wind + rain storms, the 2nd floor bath fan leaks water. I think this water is injested rain from the ridge vent. Perhaps due to incorrect shingles put on ridge vent? Dunno!

I had the roofer/contractor come by 3yrs ago when this first started. He put some roof cement around a chimney flashing in the same area [above & just west of 2nd flr shower]. He has since left town & moved to TN, as there's supposedly work down there, but not here.

Subsequently, my buddy & I went up on the roof a year & a half ago, and applied roofing cement to areas above the 2nd flr shower that appeared to have cracks in the shingles [the shingles are 30yr IKO architectural-appearance asphalt shingles, all new @ time of addition (2000)].

Unfortunately, none of these fixes have helped: 2nd floor bath fan leaks water, during & after high wind + rain storms.

Please advise your thoughts & remedies!

MY HVAC person can't find the roof termination cap you have a picture of. I can't either. Do you have any links? I'm having trouble with my present cap as far as rain coming in in windy storms, and condensation. (Kitchen vent, no attic space).

To Steve, (Jan 11) if your second story pipe vents through the soffit, then the ridge vent has nothing to do with the leak. I'm guessing this is more likely to occur when it's cold, indicating a condensation problem problem in the pipe.
As I described on Jan 11 and George posted Dec 5,2007 your pipe may be filling up with water and the pressure of the driving wind may be blowing it back into your bathroom. Check to see if your pipe is full of water but be careful, it truly may have 2-3 gallons of water in it.
As for concerns about your ridge vent leaking, check it during a driving rain storm. I know it won't leak often but try to check it when it is leaking.

I have an existing fan that is exhausted incorrectly to a soffet. Is it possible to vent it to a PVC plumbing vent pipe sitting right next to it? Thank you.

I want to install a ceiling exhaust fan in the 1st floor bathroom of a 2-story house. There is no existing fan, but I cannot figure out how to vent the fan to the outside. The bathroom in the center of the house and not close to an outside wall.What do you suggest?

Do any bathroom vent fans vent from the top of the unit instead of the side?

Mike

My bath fans were venting into the attic. So I went to hardware store bought a kit. The kit included a dampered roof vent & 4" flexible hose. My fan has a 3" outlet. So I decided to slide my old 3" pipe into the new 4" pipe and duct tape the joined area. To me this seemed like a good solution, after all it is just air venting out. But what do you think?

am installing a bathroom exhaust fan in a reno project. do you vapor barrier over the exhaust fan and put insulation over the fan box or just put insulation over it?

can i vent my bathroom fan to the garage or tie in to the dryer vent?

Is it appropriate to tie into a dryer vent a few inches from the exterior wall with a bathroom exhaust vent?

Don Aston: It looks like a Fantech Roof Cap, especially since he was using a Fantech inline fan. www.fantech.net, I found it under Accessories - Exterior Vents. Hope this helps.

I live in a 32 year old house and neither of the bathrooms have an exhaust fan. How important is it that I get one installed??

to MICAHEL re: 2 fans, one duct

As long as both fans have flappers at the housing (most newer fans do), then you're okay merging to vent ducts.
The only issue (aside from needing a flapper at each fan) is the 4" duct. If you have high CFM fans, they may operate at less than full capacity when both fans are on.

My wife and I recently moved into what is commenly known as a garden level aprtment. This means that the windows are at ground level while the remainder of the apartment falls below ground level. I have discovered that the exhaust from the bathroom exhaust fan is being vented right above the living room window. This causes problems when the wind blows exhaust back into the living room. Is this up to code? couldn't they, or shouldn't they have vented to another location?

Thanks.

Would it be useful to install attic turbines that keep running with air movements? and do the bearings get worn out and produce noise with time? if so are the bearings replaceaple or I shold change the whole unit(s)?

Well I made a mistake by pulling out my old exhaust fan instead of replacing the motor (Which I realize was possibly afterwards)
My problem is that all the new Exhaust fans are made to be nailed on the opposite side (There is not stud) and the exhaust exits the opposite side!

How do I go about fixing this without cutting open the ceiling and basically have the fan against the wall instead of centered??

Thanks for any tips and suggestions all.

I just had a bathroom fan light installed which is supposed to be rated at 100 cfm. The room size is about 9 x 10. After installation the fan will not even hold a tiny piece of tissue paper against it when I try to test the air flow. It does not appear to be working at all. How do you know if the fan is working properly? I paid the installer and wonder if it is the fan or the installer. Help!

I live in a 3 floor condo, on the second floor. I installed 2 bathroom fans and both make a knocking sound when the wind blows. I was told this noise is coming from the flappers. Can I disconnect the flappers or is there another solution. Thank you

I am installing a new bathroom exhaust fan in my master bath. Above, in the attic, a 4" flexible duct already exists and is used by the bathroom exhaust fan down in the lower level. Can I use that same ductwork for the new fan? If so, if I connect to it at 90 degrees, will it still vent properly? Thanks so much.

The exhaust fan in the main bathroom makes so much noise and does not exhaust the room. I am not sure of how can I handle this problem? Where can I start to make this fan properly exhaust and stop the loud fan sound.

We've just moved into a house a found the ventilation system from the bathroom into the attic has a flexi tube attached to it, with no insulation and no where for the air to go. We are going to get a roofer to fix a vent-cap, but please tell me what sort of insulator we can get to cover the flexi tube efficiently to avoid condensation build up.

I recently installed a bathrm exhaust fan in my bathroom. I have noticed that when my whole home ac unit is on the outside vent stays open just slightly. when i turn off the ac it closes? how can i fix this problem?

I live in a House in a Cul-de-Sac in Miami. Don't have any Bath exhaust ventilation in any of my two bathrooms and there are strict rules in the community regarding altering the houses roof, so I can't install a vent flashing on the roof. ¿What can I do?

I'm installing a bathroom ventilation fan as well as a dryer vent. Is it possible to just vent these in a single hose or would there be to much condensation/lint buildup?

Okay, so I understand all the cautions about soffit vents and bathroom exhaust, with regards to moisture.

However - I have a first-floor half-bathroom (in a two-story house) at the front of the house, and I need to install some some sort of 'stink vent', since there is no fan. I think I could just barely manage to squeeze a small fan-duct combo in and vent out a soffit vent.

Given that there will be no shower steam needing to be vented, are there likely to be problems with this sort of approach? Failing this, I'm not sure what else to do.

My bathroom contractor told me that he uses the toilet vent to vent the fan so that he doesn't have to go through the roof. This doesn't sound right to me. Is this an acceptable option? I'd rather not have it vented through the roof (my roof is only 4 years old. I've heard of venting through the soffit and a gable vent. Would one of these options be OK?

Two questions:

How do I insulate a tee (joiner that turns one duct into two channels)? All the tee's that I have found are sheet metal, so how do I insulate them? Spray foam seems like it would slip off or be imperfect.

Do they make a four manifold instead of a tee that only does two channels? I want to have four different ducts running from a bathroom fan to different areas and I'd rather no have to use three tees, when it seems like there would be a four port joiner out there somewhere.

Thanks!

Tim, I have a four inch glavanized vent going from my garage through the roof of my two storey home. We recently replaced the furnace with a heat pump locating the new air handler in the attic. I would like to use this vent to exhaust my clothes dryer. I would install a tee at the bottom with a removable cap for cleaning. I am in So california, so cold temps are not a major factor. Do you think it would be wise to use a PVC cap at the bottom with a connection to a drain in case of any condensation?

micahel, the roof vent needs to be rated for two bath fans. this typically needs a motorized roof vent.

What should I use to treat existing mold in the attic?
The cause is vent fans that vent into the attic, this problem will be fixed. I am concerned that treating the mold with bleach+water will only add more moisture to the attic & saturate the insulation. Thanks

I have installed a bathroom exhaust fan in an insulated ceiling. How do I properly vapour barrier this fan box in the attic? I live in a very cold climate and want to stop as much cold air as possible from entering the house. The fan has a damper as well as the roof vent, I plan to insulate the duct too, but know that I need to vapour barrier it. I bought a blue poly boot, but can't find instructions on how to install it around the exhaust fan. Any and all help is greatly appreciated.

I realize this is an old thread, but it's still out there when searching for this type of answer. The comment posted by micahel 09Dec2007 about tying in to an existing duct. I would think this would be possible providing an inline back draft damper was installed close to the new T junction for the additional vent duct on the side closest to the existing fan.

I am planning on installing a bathroom fan in a bathroom that doesn't have one. I was wondering if i can connect the fan duct work into the toilet vent pipe(PVC pipe). This bathroom has a bath but never has had a fan

would having a 4in fan reduced to 3in for about a foot right off the fan then 4 in the rest the of the way out cause the fan to be louder.if i replace that 3in section and have it all 4in would it make the fan quieter or would it not improve the quietness of the fan.

I want to install a exhaust fan in my 2nd floor bathroom. I found a verticle 4" white PVC pipe that I'm pretty sure vents my 1st floor bathroom plumbing out through the roof. Can I just tie into this pipe and save not making another hole in the roof.

regarding the insulation of the exhaust vent duct, what kind of insulation can i use for this and is a flexible duct better than a rigid duct?

What if you have a bathroom in the middle of the house and on the first floor I have noway to access a Exterior wall or attic cause there is a bed room right above the bath room the house is an early 1800's year old farm house and the room was an after thought what are my options for a bathroom ventilation??

I have water dripping from the bathroom fan, the ducting is 4" ridge vent pipe, insulated with the"sock" type that has fibreglass inside and a black poly vapour barrier on the out side. The venting is almost vertical from the fan to the roof vent for about 4-5 ft. Insulation 100% top to bottom. Weather conditions were-28C the rose to +3C, then the dripping started. The problem is clear, condensation on the inside of the vent, then the warm air caused the melt. HOW DO I PREVENT IT? I think the fan CFM is 90, room is 408 CuFt and fan runs for at least 30 mins after a hot shower, with the fan running during it too. HELP ME, please.

I'm renting a house, and the two fans in the bathroom are very loud on days/nights that have very high winds. Is there something I can do to stop this? It's not good when the baby's room is right beside the bathroom and it wakes him up.

My client has asked me to get some opinions on whether or not she should install dampers at any of the bathroom exhaust fan terminals.

Cold air is currently coming back down the vents and into the house. We've heard mixed opinions on whether or not to install these (we're told they can freeze open and freeze shut. If we are recommended to install them can be done in the winter or if it is better to do in the summer and what should we expect to pay

Is there any problem with venting 2 fans to the same roof vent? I have to use flexible tubing due to the location of my one vent. With the tubing coming out of the side of the exhaust fans, what are my other options? I too found water in the lowest part of the flexible tubing...

What kind of spray foam do you recommend for insulating the duct? Latex? Polyurethane?

Is the roof termination cap pictured in the article suitable for very cold climates? Is there concern for the vapour condensing on the shingles and forming ice?

My husband and I installed a new 210 cfm fan in my bathroom. We used a 7" flex pipe and punched though our roof. Installed a plastic vent on the roof. Everything works great. The only problem that I am having is that I can hear the rain and wind. Is there anything that will help with this? We did not do any insulation, is this our problem? Thanks for your help

I am installing a bathroom exhaust fan in an unvented bath. There is the vent pipe for the water. It is only a 2 inch pipe coming out the roof. Can I vent my exhaust fan into this smaller pipe? It seems like it would be good enough and the p traps would stop any air flow coming back into the bath.

I also have the same situation as Larry L. from Bloomfield ,MI from your Bathroom Fan Ventilation column.I need to vent an exhaust fan but I have a flat roof above my bathroom not a pitched roof like your example shows. Thanks

Bathrooms are particularly prone to moisture problems caused by high humidity. Heat and moisture combine to produce moisture-laden air that fills the room and, upon contacting cooler tile, walls, and ceilings, condenses, turning back into water.
This feeds mold, mildew, and even structural rot. To expel humid air before it has a chance to condense, every bathroom needs ventilation. In most cases, the best ventilation for a bathroom is an exhaust fan.

Though the bathrooms in most new homes are equipped with adequate bath fans, an older home is often either entirely without a fan or has one that is underpowered. When buying a new ventilation fan, be sure to check its rating for air movement, which is measured by cubic feet per minute (CFM). For an average-size bathroom, the minimal requirement is 80 CFM.

Replacing an existing fan with a new one is a relatively easy do-it-yourself project as long as the new unit will fit in the existing opening and can be connected to the existing exhaust duct.

Installing a new fan where there wasn’t a fan before is more involved but often easiest if you place it where there is an existing ceiling light fixture. Before you install the fan housing, the job will require cutting a hole in the ceiling at the light fixture’s location, snaking a vent pipe (or duct) from there to an exterior wall, penetrating the exterior wall for the vent, and adding a vent cap. For this job, purchase a fan that has a built-in light to replace the light you remove. If the ventwork is beyond your skill level, call in a contractor.

http://www.ring4van.com/

If you want a ventilation fan with a true damper, check out the ventilationt fan\damper insert offered by Larson Fan Company. This true damper prevents hot humid air from wicking in and will reduce the amount of time your air conditioning will run, saving you a lot of money on your utility bill.

As a contractor and instructor in Northern Alberta, I am pleased to say that this is one of the few sites that actually offers reasonable and correct information on Ventilation. Smooth pipe is always preferable to flex. I like the idea of the spray foam, good idea for the homeowner!
Keep up the good work Tim!

Hi,
I live in a 1939 bungalow that doesn't have a bathroom fan and I was thinking of installing one. My question is: If I were to install an in-line fan and have it vent through an existing roof vent, could I tie in an additional hose to also vent my attic? I have a number of roof vents and I know that it gets pretty humid and hot up in the attic and I was thinking of installing an attic fan...but if I could solve both problems with one fan I think that would be preferable. Any suggestions on if this is viable and how I would go about doing this? Thanks all.

Is it possible to vent more than one bathroom vent fan to one roof vent? I have three fans that are currently venting down into the soffit (not through to the outside). I was considering adding soffit vents, until I read your comments. Should I add three separate roof vents?