Bath fan venting

I know the latest code requires bath fans vented to the outside. 33 years ago, this was not the case, could be vented to the attic, passed inspection, perfectly legal. If I sell a 33 year old home vented to the attic, am I REQUIRED by home inspection to modify and vent outside now? Or is original install grandfathered in? There have been no modifications to original fans/vent to attic.
Thanks, Don

You are not required to do anything by a home inspection.

A home inspector will suggest the bath vent fan should terminate at the exterior.

Michael is correct and I would recommend that it exhaust to the exterior…probably the gable, depending on the attic. I can’t imagine it would be very costly. How bad do you want to sell your house? Or, maybe the buyer won’t care about it. :slight_smile:

As Mike and Larry have said, as a homeowner/seller you are not “required” to repair anything a home inspector may discover while inspecting your home. We are just home inspectors hired to observe and report on the condition of a home. We are Not code enforcers.

But to keep the buyer from walking you may choose to compromise.

I always call it out even when it seems the vent terminated in the attic for decades with no apparent ill effect.

My bath fan vents to attic. My then home inspector told me. I made a note of it, but I didn’t consider it a big deal as it’s a simple fix.

7 years later, it’s still not fixed, but my kids never remember to turn on the fan anyway. :stuck_out_tongue:

Hi Don!
You are correct bathroom venting to the exterior is a requirement. If you found this “issue” you can bet your life that when your home is expected it will also be found.
NOTE: This is such an easy fix that it can be completed for approximately $50.00-$75.00

All of the home inspectors on this message board are also correct in the fact that “when your home is inspected” you are not REQUIRED to correct anything on your home inspection report.

Also no one fully explained why it has to be “exhausted directly to the outdoors”.

The other inspectors have stated “correctly” that no one can force you to abide by the home inspector’s report. And certainly no one can force you to correct the deficiency!

That being said…… If it is in the home inspector’s report it will be a “matter of record” from this date forward. If someone buys your home and there is a “mold problem” in the future… Well…. I guess you get the picture!

PS: This is such an easy and inexpensive fix that it hardly bears mentioning. No matter what you do ….I wish you the best of luck!

Also I have included the code in question so that you will know that the “future home inspector” will not be just “whistling Dixie”.

[FONT=Arial][FONT=Times New Roman][/FONT]]([/FONT]

Here is an “educational video” that will explain it in detail.
[FONT=Arial][FONT=Times New Roman][/FONT]]( [/FONT]

Bathroom Ventilation

2009 International Residential Code
Part V – Mechanical
Chapter 15 Exhaust Systems Mechanical Ventilation.

M1507.2 Recirculation of air.
Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

Area to Be Ventilated:
Bathrooms – Toilet Rooms = Mechanical exhaust capacity of 50 ft. cubic feet per minute intermittent or 20 ft. cubic feet per minute continuous.

I know you will do the right thing and …Once again… I wish you the best of luck:nachi:

PS: When you request an inspection be sure to ask for an InterNachi Certified Inspector. Or… Make sure that your “buyer” hires one!
You certainly do not want some “candidate” and or a so-called “full member” from a known diploma mill Association.

If you can go on the Internet and become a “candidate/inspector” just by supplying your credit card information and paying the entrance fee… well… I guess it is self-explanatory;-)

Here in NH we have a weatherization SOP, in that SOP for bathroom venting the standard practice is to use a four inch ridged metal pipe and vent the fan directly through the roof above the fan with limiting and elbows, usually one at the fan box itself. The metal pipe is the wrapped in fiberglass insulation and taped with aluminum tape, a roof termination kit is installed on the roof.

Additionally any fan that is not at least 110 CFMs is replaced.

I’ve installed alot of fans this way and it really work well, especially insulating the pipe to prevent condensation during cold weather.

Frank C gives some excellent info here.

Here’s a small article that explains it as well

As already stated you’re not “required” to fix anything, on the other hand if the buyer makes an issue of it offer him a $100.00 or have a Qualified Contractor come in and terminate it to the exterior. If you have good insulation make sure the contractor doesn’t damage it by compressing it.

Most homes in my area route the vents through the side of the house, which IMO is preferable as to keep the protrusions through the roof at minimum, reducing the chances of a potential leak point.

"Also no one fully explained why it has to be “exhausted directly to the outdoors”.

OK here goes, a bath fan is exhausting very wet, humid air from the bathroom, all that steam you raised during your 20 minute hot shower. Once that humid air hits cold air inside your well insulated attic, it will condense and possibly even turn into an mini rain or snow storm, or it will condense as dew or frost on top of your insulation or on the bottom of your sheathing. Once this stuff gets wet nothing good happens.

The thing to remember about codes is that they are pretty much always reactive. Builders did something a certain way because it was convenient, cheap, ‘we always did it like that’, over time it is found that doing it one way causes problems that can affect safety and value of property, but doing it another way solves the problems. After a lot of debate between all affected parties a code is (maybe) changed, long after the horses have left the barn. Codes are seldom retro-active simply because it is too difficult to enforce, not necessarily because it is in everyone’s best interest. Sometimes a new problem emerges because technology changes, in those cases it may not be necessary to upgrade, as far as the bath fan in the attic, I can’t see a good reason not to upgrade if you live anyplace where the outside temperature is much below the inside temperature for some part of the year (or you never take baths or showers:-).

Check your local AHJ or code enforcement office. Most all areas vary on this subject. Personally, here in the Midwest, I do not recommend venting fans to the outside.

Most of the time, routing vent fans “outside the living envelope” will suffice. If the bathroom is below ground level, such as basement, it will have to route outside through the sill/ledger plate. If the bath is on the main or upper level, venting to the attic is fine, with me. Why?

One of my agents sold a home, and another inspector inspected the home, and recommended vents installed through the roof. Weeks later the home owner complained about her bathrooms being cold. Extending the vents through the roof caused the stack effect, much like a chimney with an open flue. She had them removed from the roof, roof holes sealed, and problem of cold bathrooms solved. Good subject to discuss here. As in another post, I have seen 30 year old attics with no problems, and bath vent fans terminating at the upper roof attic.

Saw a ten year old ranch 3 bath home with mould so severe they had to rip off the roof sheathing. Venting into an attic is just not a good policy. All bath fans here have a flap that opens when the fan starts and while admittedly a good stiff breeze through the home might cause it to open too, unless the woman lived in a wind tunnel the stack effect doesn’t take place. I have seen literally hundreds of attics with mould issues where bath fans dump into attics or into vented soffits. Just a bad idea all round.

All venting of such shall be to the exterior.

Excuse me but I am confused. You repeat my question from my post #7. *

Then you go on to explain why bathroom exhaust/venting to the outside is required.

Here is where I explained it in my post #7.
Quote FCarrio:
Also I have included the code in question so that you will know that the “future home inspector” will not be just “whistling Dixie”.](

Here is an “educational video” that will explain it in detail.](
End Quote

This is fully explained by Michael’s article that is posted on this website.


I thank you for your explanation it was very well done.

With all due respect …My question to you is……* Did you not watch the videos* that I provided ?
Did you not click on the link that Michael provided?

If you had you would have known that this question had already been answered.:wink:

No I did not Frank, sorry if I offended you. I prefer a simple, written, plain language answer to a simple question to clicking on links and watching videos, and I like to think (perhaps I am wrong?) that there are more like me who might appreciate the same, so as a public service I provide an answer that does not require leaving the forum. Different strokes for different folks.

Hi Eric!
First of all I want you to know that I am not “offended” in any way shape or form.
I enjoyed your explanation and found it to be accurate, factual and informative.:smiley:

Believe it or not I also realized by your explanation that you had not bothered to look at the videos that I have provided and that you have not bothered to look at the link that Michael had provided.

The videos and Michael’s article explained the situation in great detail.

What was the reason for my post to you? I was trying to point out in “a friendly non-adversarial manner” that you had not paid attention to detail.
{There is an inspector who frequently posts on this message board. It is apparent that he just “charges straight ahead like a bull in a china shop” without giving any thought to what he is saying and more importantly… he does not pay attention to what other experienced and qualified have said before him!.
I did not want you to pick up any bad habits from him!}

I have been in this industry for 42 years and I have seen inspectors come and go.
*I believe that you are one of the “good ones” *and I hope that you are successful in this business.

I was just trying to “make a point” in the friendliest manner that I know how.:wink:

Warmest regards, Frank:nachi::nachi:

Different areas may cause different results but in Kansas City in the past 25 years in my area I’ve personally only seen bath fans venting into an attic be a problem 2 times AND most fans are vented there. My report comment is:

FYI - Bathroom exhaust vent(s) terminate in the attic. Although often done this way, current building standards require extending these to the exterior for reasons such as: helping to lower humidity levels in the building; move condensation outside; reduce the likelihood of mold; etc.

Erik, I do get where you’re coming from, and your preference is a short simple answer. But you don’t need the answer, the OP did.

Just saying “because it causes moisture” would not be doing our best to help the OP, who is a non-member seller.

So we explained why, with links, educational videos, etc. With this information, he would be well informed and start working on how or if he wanted to correct it.

I would imagine the OP did read the links and watched the videos, and viewed the responses. Remember, he’s not a home inspector, and he was looking for an explanation, not a narrative for a report.

Just my 2 cents…