Professional Saint Louis, MO on Nov 26, 2012

Is Your Bathroom Properly Ventilated?

We've seen it probably more than 100 times. In an attic, the bath fan discharges directly into a pile of insulation. You would be surprised that it's more common than many people realize! If you don't know the condition of yours, it's worth a quick investigation. So, what are the indicators of a properly ventilated bathroom? Here are a few tips.

1. Select the correct size bath fan. Many have a square footage chart included at time of purchase, but there are tables available online as well, such as this one from HVI:

http://www.hvi.org/publications/HowMuchVent....

2. Ensure adequate make up air can reach the fan. As pictured, allow a minimum of 3/4" clearance under the door, and even more if possible. Use caution, however, that hollow doors only have a small solid rail at the bottom which could limit the cut off.

3. Always terminate the ductwork to the home exterior. In the photo, the duct is attached to a pre-cut galvanized sheet, and connected ...»

22 Comments

Becky J Troy, IL

my bathroom fan is only ventilated to the attic. I never understood why you would want moistness sitting around up in the insulation. We did get a new roof last year and I questioned the roofer about ventilating it to the roof, but he didn't seem too interested.

on Nov 27, 2012 · Like 1
Douglas Hunt New Smyrna Beach, FL

I love the preset timers for fans. A friend has one and that is definitely what I will do in the future.

on Nov 27, 2012 · Like 2
Building Moxie Baltimore, MD

very well laid out post Paul and super tips. I know myself when I recently installed a door on our bath that I wasn't necessarily conscious of a full 3/4" clearance (will check when I get home). Another thing we are guilty of in our house (all of us) is showering with the door open. I know that I upsized slightly when I selected my fan, but I did not take this into consideration. wish I would want have gone even bigger. I can't necessarily assume that we are in the minority, but I'd love ...»
to hear... and I'd be curious if there are any suggestions that address this use case specifically - other than "don't do it." As for a timer I do not have any installed in my house, but it is on my long to do list. You know SLSConstruction did a "How to Install" on our blog ... he calls a bath fan timer, "His number one piece of advice to improve indoor air quality, comfort, and to help save energy." (Number 1). cheers.

on Nov 27, 2012 · Like 1
Building Moxie Baltimore, MD

One other note on this, I always prefer to exit the house on a vertical surface if at all possible as opposed to through the roof (for obvious reasons) ... wonder if there there is more of practical reason for going up instead of out. cheers.

on Nov 27, 2012 · Like 1
Miriam I New York, NY

Great tips, Paul! Thank you for the advice!

on Nov 27, 2012 · Like 2
Barbara Kalyta Canada

My powder room is not vented and usually smells horrible. The toilet also is constantly plugged up. Nobody should have to use a plunger as often as I do. I have no idea of what needs to be done to fix it. The room is in a former carport. Over the packed dirt is a heated floor with ceramic tiles. Above is the upstairs and since this was a former cape code with multiple renovations, going straight up through the roof is impossible. Any ideas of what needs to be done?

on Nov 27, 2012 · Like 1
Becky Blair, NE

Thanks for the great info Paul.

on Nov 27, 2012 · Like 2
Sharron W Memphis, TN

Hamtil Construction LLC This is SUCH great information! Our house is so old and I am confident that the bathroom fan is not properly vented....the Master Bath doesn't even have a fan because it has a WINDOW, now even in the 70's when this place was built I'm pretty sure that was a stupid "code" simply because who wants to open a window during January.... I left the window open the other night and forgot to close ...»
it....I thought hubby was gonna die the next morning getting ready for work...LOL

Barbara Kalyta One of the first things I did to stop the "overflowed" toilet syndrome was change toliet paper! When my kids were teens I switched to the scott 1 ply and I haven't had a problem since... Your's may be a the air vent is clogged with leaves or what have you...but a simple change in tissue types helped us...

on Nov 27, 2012 · Like 2
Cherie Dunkel-Hoysock Pottsville, PA

I am currently remodeling my home that is attached to my neighbors. I do not have ventilation and plan on installing one. However, we share a sewer and everytime my neighbors flush their toilet I lose my water in my toilet and it always smells like mold and mildew. I can not leave the toilet seat down because the seat and lid will be full of moisture and grow mold. Any clues??? please help!

on Nov 27, 2012 · Like 1
Peter Klarman Bayside, NY

When my first floor and basement bathrooms were renovated the first task was to vent the first through the roof and the basement through the brick wall.

on Nov 27, 2012 · Like 2
Erin H Las Vegas, NV

I learned that trick from Mike Holmes and none of my bathrooms are properly ventilated. They don't really take pride in the housebuilding anymore. The developers just want to crank out as many houses as possible to make a bunch of money. My house is less than 10 years old and there are SO many problems with it! I don't even have an access panel to get to the plumbing in my tub and I'm sure that there is mold under my shower pan.

on Nov 27, 2012 · Like 1
Hamtil Construction LLC Saint Louis, MO

Becky J Well, it's not really a good idea to have it discharging into the attic. Code requirements for us dictate that it must terminate to the exterior, and that is the ideal way to do it. If you are still inclined to vent it correctly, even if you have a new roof, it's not too late to have someone such as a remodeling contractor come install a roof vent and associated ductwork.

on Nov 27, 2012 · Like 0
Hamtil Construction LLC Saint Louis, MO

Thanks for the feedback Building Moxie, and I have read that post by Sean, which is a good one on the topic!
http://www.buildingmoxie.com/2012/06/install... ...AND, ...»

I would say that the best way to vent a fan is via the shortest and most straight route possible, whether sidewall, eve, or roof. For us, we prefer to go horizontal through the wall, but usually it's all dictated by conditions of each project.
Also, some fan housings will allow you to upsize the motor only, for instance, you can change a NuTone 80CFM (QTRN080) with a 110CFM (QTRN110). They use the same size housing and ductwork. For yours, I would call the manufacturer or distributor to make sure.
No shame in leaving the door open, either. You will get plenty of makeup air!

on Nov 27, 2012 · Like 1
Hamtil Construction LLC Saint Louis, MO

Barbara Kalyta Sorry to hear about the issue. To me, it sounds as though you may have a plumbing vent issue, which is separate from a bathroom fan vent. While a vent fan may help with the odor, the real issue here might be in the pipes. Just a guess, but a plumbing vent is the pipe that extends up to the roof of your house and furnishes make up air when you flush the toilet. Without it, toilets will flush slowly, gurgle, and ...»
sometimes the water that rests in the u-shaped trap below the sink and in the body of the toilet will get siphoned out as water is flushed down the drain from other sources. Also, occasionally in bathrooms that are used very infrequently, the water which rests in the trap will dry up enough to allow the sewer gas odor to escape. This is a bigger issue during winter in our region, so in Canada, there might be a larger risk. I would call a licensed plumber to come take a look and verify the venting.

on Nov 27, 2012 · Like 0
Vicki Smyrna, GA

ty for sharing. we learned from weatherization that it should go out of the house, not to the attic. we have timer to turn one hour before we go to shower. we are thinking to have humidity sensor bathroom fan exhausted to turn on by itself whenever there is humidty. is it worth to have it instead of timer?

on Nov 27, 2012 · Like 0
Hamtil Construction LLC Saint Louis, MO

Sharron W Thanks for the feedback! Interestingly, building code in many places states that you can forgo the bath fan if there is fresh air in the room, i.e. from a window, and that it is large enough to accommodate the square footage of the room. We always insist on adding a fan regardless, though, just for the reason you mentioned. Who wants freezing air blowing in a window during a shower?!?

on Nov 27, 2012 · Like 1
Vicki Smyrna, GA

they from weatherization used incense to test but paper is very good idea. they put duct from bathroom ceiling toward to eave instead of to the attic.

on Nov 27, 2012 · Like 0
Hamtil Construction LLC Saint Louis, MO

Cherie Dunkel-Hoysock That is a new one for me. You mean that you share a sewer lateral in the yard out to the main sewer line? Is it undersized? Have you had a drain inspector run a camera or snake through the line?
If water is siphoning out of your toilet, it seems that you may also have a plumbing vent issue such as I described above to Barbara K. If you are renovating currently, can someone investigate ...»
if the bathroom has a plumbing vent and that it is sized properly and not obstructed? I have seen them filled with acorns, sweetgum balls, and other crazy stuff, so that may be a possibility here as well.
As far as the moisture and mildew, I am not sure. I suppose that if there is sewer gas escaping, that it is warmer, moist air which may be condensating on the colder lid?
I am going to tag Woodbridge Environmental Tiptophouse.com to see what his thoughts are as well.

on Nov 27, 2012 · Like 0
Hamtil Construction LLC Saint Louis, MO

Good tips Vicki and thanks for adding to the discussion. The smoke test for fans is a good one, and I would say is more reliable, especially when checking the make up air under the door. I have seen home performance inspectors do that one as well.
The humidity sensor would be a step above the timer. It would run for the right amount of ...»
time, as long as the set point was correct. In my opinion, it might be a bit much for a typical bathroom use scenario, but not out of the question for a thorough and "hands off" solution... meaning you just set it and forget it. I could see this working best in a bath with a separate fan in a toilet closet.

on Nov 27, 2012 · Like 0
Building Moxie Baltimore, MD

thanks Paul @ Hamtil Construction LLC it did get me thinking ... excellent tip on looking at swapping out only the motor. I'll look into it. cheers my friend.

on Nov 27, 2012 · Like 1
Cherie Dunkel-Hoysock Pottsville, PA

Hamtil Construction LLC, yes we literally share a sewer. The homes were built in 1896 and it was a family who built them side by side. So the sewer is shared from the second floor bathroom all throughout the house and then the actual pipe starts coming out in their basement, transfers to my house and along the wall in my basement, then out under my front porch steps and across the neighbors pavement into the main sewer in the street. It's a nightmare:-(

on Nov 27, 2012 · Like 1
Becky J Troy, IL

Hamtil Construction LLC, well you don't really live that far away from me! Will keep you in mind should we decide to ever do it. (I have declared 2013 as a no home improvement year, lol)

on Nov 27, 2012 · Like 2