Reuben's Home Inspection Blog

head_left_image

Forget Code, Bathrooms Need Fans.

For the last 800 years, building codes have allowed bathrooms to be built without exhaust fans.

Exhaust fans aren't even a requirement here in Minnesota!  This is a great example of how building codes are only minimum standards. I thought about this while doing a home inspection at a rental home in Minneapolis.   The outdoor temperature was about 45 degrees, and every single window in the home was covered with condensation, which was also dripping down the walls.

Condensation on a window in Minneapolis

Oh, and there were no fans installed.

Bathrooms need exhaust fans to help eliminate moisture problems, plain and simple.  When people take showers and baths, moisture gets pumped in to the air.  During the winter, this moisture condenses on windows and walls, and often makes it's way in to the attic space through attic bypasses, where it will create frost.

Minnesota requires windows in bathrooms that provide a total glazed area of at least three square feet, and half of that must be openable.  The exception to this rule comes when a bath fan is installed that will exhaust at least 50 cubic feet per minute, or a continuous exhaust system such as a Heat Recovery Ventilator exhausts at least 20 cubic feet per minute.

The idea of someone actually opening a window on a cold winter day in Minnesota to help reduce moisture in the bathroom is ridiculous.  If you live in a house without an exhaust fan in a bathroom that gets used for showers or baths, install one.  Your house will thank you for it.

If you're going to install a fan, here are a few tips to make sure your house is happy with the fan.

  • Choose a good fan. You'll want to balance noise level, performance, and price.  If you buy a cheap noisy fan, you probably won't even want to turn it on.
  • Make the exhaust duct short. A proper exhaust duct will be as short as possible and take as few turns as possible.  The longer the duct and the more twists and turns it takes, the less air flow.  A fan rated for 80 cubic feet per minute (CFM) assumes the fan has no duct.  As soon as a duct gets added, the actual CFM goes down.  I've inspected hundreds of houses where there is barely any air flow at bath fan exhausts.  If the bath fan is located in the basement and the duct runs up to the roof at the second story, air flow will be pretty pathetic.
  • Waterlogged Duct Insulate the duct where it passes through unconditioned spaces, such as the attic.  If you don't, moisture will condense it the duct, and might drip down and stain the ceiling. I once inspected a house in Richfield where the exhaust duct was uninsulated in the attic, and so much moisture had accumulated in the duct that it was completely filled with water!  The photo at right shows me holding my flashlight up against the duct - this is one of my favorite photos ever.  Click the thumbnail to see the full version.
  • No Switch Don't use a standard switch to control the fan. When a single switch controls the fan, people turn the fan on while in the shower or maybe after the shower, and turn the fan off when leaving the room.  The problem is that the fan doesn't run long enough to remove enough moisture.  A better solution would be to install a timer that runs for at least a half hour, or install a humidity sensing fan.

Reuben Saltzman, Structure Tech Home Inspections – Email – Minneapolis Home Inspections

RELATED POSTS:

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 17 commentsReuben Saltzman • November 17 2009 06:37AM

Comments

Thanks Reuben!  Great information....

~Deb in Cape Coral, FL

Posted by Debbie Cullen, Your Cape Coral, FL Specialist (REMAX Realty Team-Cape Coral, FL) over 8 years ago

Thanks for sharing. Bathrooms really do need fans. However, many older homes do not have them.

Posted by Roy Kelley, Roy and Dolores Kelley Photographs (Realty Group Referrals) over 8 years ago

Reuben,

I viewed a townhome and notice the exhaust fan from the downstairs bathroom vented into the living area. not exactly the best way if one had company over and everyone was in the LA!!!

Posted by Pat O'Reilly (RE/MAX..214-289-6176 Irving and all of Dallas Fort Worth) over 8 years ago

Reuben,

I agree with you that bath fans are important.  There are older homes here that dont' have them and you can tell the moisture just hangs out.  I didn't know about the length of the duct being an issue but it seem pretty logical.

Posted by Brian Brumpton, Boise Idaho Real Estate (Keller Williams Boise) over 8 years ago

That is what the window is for.  Just open it up and the moisture goes away NOT.  Thanks for the info.

Posted by Gene Allen, Realty Consultant for Cary Real Estate (Fathom Realty) over 8 years ago

Reuben, so true----and crank up the heat in there too while you are showering.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 8 years ago

Debbie - thanks for reading.

Roy - I'm trying to change all that.

Pat - What's the point?  Better to have no fan at all!

Brian - I can definitely 'feel' when a house has a moisture problem right after I walk in the door sometimes.  I know exactly what you're talking about.

Gene - especially not during the winter.

Charles - yeah, whatever you can do to get more moisture in the air, right?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 8 years ago

Hi Reuben, very enlightening post. I am suprised that there is not more fans in a home to pull the moisture out.

Posted by Charles Stallions Real Estate Services, Buyers Agent 800-309-3414 Pace and Gulf Breeze,Fl. (Charles Stallions Real Estate Services Inc) over 8 years ago

I totally agree, a fan should be required in a bathroom. A window is useless as ventilation.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 8 years ago

Hi Reuben,

Terrific post!  Thank you for sharing the information with us! 

Chris

Posted by Chris Minion (O'Brien Realty) over 8 years ago

Joyce - me too.

James - they're nice in the summer if you don't have the AC on... that's about it!

Chris - thanks for reading.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 8 years ago

Note this comment you included; "When people take showers and baths, moisture gets pumped in to the air.  During the winter, this moisture condenses on windows and walls, and often makes it's way in to the attic space through attic bypasses, where it will create frost.

What I find ironic is 90% of the homes I've inspected have the fan exhaust terminate in the attic, many times buried in a foot of insulation, instead of to the exterior. This is true with high dollar homes as well as average priced. Unable to comprehend the reason builders choose this method.

How many of you (inspectors) write this as a defect?

I do.

 

Posted by Christopher Currins, Metro East Home Inspector - IL. (CBC Home Inspections) over 8 years ago

Christopher - you've gotta be kidding me!  If the bath fan doesn't have an insulated duct that's tightly connected to a functional dampered roof cap, I write it up.  What does your local building code require?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 8 years ago

One thing that can help is to turn on the forced air furnace blower (if the thermostat is set up to do that).  It won't help over all humidity in the house, but it will keep it down in the bathroom.  I personlly use both.  I also use the furnace blower to filter the air (use a good filter), keep air circulating and distribute heat from solar or wood heated rooms to the rest of the house.

Posted by Ralph Brady, The premier inspector in Humboldt (Brady Home Inspection) over 8 years ago

Ralph - yes, using the furnace's blower fan will do all those things.  Not very well... but it works.  A device that is actually made for doing this is an HRV.  I'll be writing a blog about those soon.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 8 years ago

I turn the fan on and then go searching for them.  Frequently, in homes that are 20 years old or more, the outlet has no duct and it terminates directly into the loose fill insulation.  In this instance, with a homeowner performed basement remodel, it was neither mounted nor ducted.Bathroom exhaust fan

Posted by Hank Spinnler, Atlanta Home Inspector (Harmony Home Inspection Services of GA) over 8 years ago

Hank - I do the exact same thing!  I start every inspection by walking through the house and turning on every fan, dryer, and anything else that removes air from the house.  Then I go outside and verify they're all working as I inspect the exterior.  I find a ton of what you pictured above!

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 8 years ago

Participate