Thread: Bathroom Exhaust to Roof Passive Vent

Is it allowed to run a bathroom exaust vent duct up to a passive roof vent or a ridge vent? I expect this is close to the requirement to exhaust directly to the outside, but not quite right. It seems to depend on the interpretation of "directly to the outside". At least it doesn't exhaust to the floor of the attic like most.

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That's exhausting to the attic ... almost ...

As that is blowing the exhaust air directly to the flat top of that vent, and the vent opening is so large, most of the bathroom exhaust air is being blown back down into the attic, and:

- M1501.1 Outdoor discharge. The air removed by every mechanical exhaust system shall be discharged to the outdoors. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.
- - Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.

- M1506.2 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.

They do this all the time. It's not right but no one cares. If you look at this in some older homes you can find some signs of moisture damage to the wood around it. It can add moisture to the attic. I always comment on it.

Thanks for the quick response. I did write it up, but is nice to get additional views from the "experts". To make things worse, these two vents were near a ridge vent.

Around here I would be pretty happy they even did THAT. Most of the time the vent is buried under the insulation.
Not sure I fully agree with Jerry that that vent hood would not work OK. After all, all of the vents have to have some sort of termination point. But, like I said, that installation is much better than what we see around here most of the time.

Jack, Same here. Almost hated to write it up since the builder at least tried to get it out of the attic.

Originally Posted by Jack Feldmann

Not sure I fully agree with Jerry that that vent hood would not work OK.

Jack,

That would work okay if the bottom of the vent was enclosed and the exhaust duct was sealed to it to keep any air from discharging (blowing) back into the attic.

The problem with those vents, versus the curved goose neck type, is that the air is simply being blown 'at the flat surface' of the top of the vent. Sure 'some' air will be blown outside through the opening around the vent top, but a lot if it will blow back into the attic. This of spraying a garden hose against the side of the house, some water does spread out along the side of the house, but most of it sprays back at you and if you are too close you will get soaked. Same thing happens with the air, only you don't see it going back into the attic.

Blowing the air against that top is not discharging the exhaust "directly to the outdoors" and does discharge air back into the attic when the code states "shall not discharge into an attic".

Then should there ever be an exhaust fan fire the flames would strategically terminate within the attic.

Exhaust vents should terminate at their own vent,usually smaller then a normal passive roof vent,that way there is no issue,as this vent is normally the same size as the discharge pipe,this installation no way affects the attic venting system

You're assuming the fan has enough uumph to actually blow enough air to bounce off the flat surface. :-) Most bath vents that I see don't move enough air to go very far at all. Plus, they are almost all in those cheap plastic flex ducts.

One additional concern that did not show in the photo. There is a fine mesh screen over the bottom of the vent at the same level as the under side of the decking. One had started to clog above the duct. This would again deflect moist air back into the attic space. But, the home is 11 years old and no evidence of moisture damage was present, so technically it is wrong but so far has caused no visible problems. I will continue to write up the situation, but not make a big issue of it.

I don't have a problem with the way that bathroom fan is being vented. Would I note it in my report? Doubtful, unless I found a visual problem. After 11 years it has passed the test of time, so to speak.

Its very common in my parts to see the exhaust vents venting in the manner shown in the photo.

The homes have been inspected by the AHJ.

I have yet to see any damage as a result of the installation.

Attics are most always under negative pressure, not to mention the stack affect.

To me its not a big deal and I no longer call such installations out.

Originally Posted by Jack Feldmann

You're assuming the fan has enough uumph to actually blow enough air to bounce off the flat surface. :-) Most bath vents that I see don't move enough air to go very far at all. Plus, they are almost all in those cheap plastic flex ducts.

If those fans don't have enough uumph to actually blow enough air to bounce off the flat surface, those fans certainly do not have enough uumph to blow the air out from under the down turned edges of that top and actually blow air *OUT* of the attic.

Whether a particular set-up has caused / resulted in damage during its installation period or not should not be a consideration whether to write it up or not; especially with a bathroom exhaust fan.
We have no idea or control over how that fan will be used. Say the house is occupied by a couple that doesn't take very hot or very long showers, or prefers to open the window a bit instead of use the exhaust fan; In that case, there won't be much moisture transfer up into the attic to cause any damage. Now let's say the new buyer has 3 teenage girls. They'll be taking lots of long hot showers if they are at all typical. This of course means lots of moisture transfer up to the attic. There could be significant rot / damage in a very short time period.
Whether we write something up or not should not be based on our own biases. If it isn't compliant or can pose a hazard, write it up. Write what you see.
Whether they do something about it or not is beyond our control.

Originally Posted by Markus Keller

Whether a particular set-up has caused / resulted in damage during its installation period or not should not be a consideration whether to write it up or not;

That goes right along with what I frequently say: That 'passing' the "test of time" is the wrong way to say it and to look at it. Something does not 'pass' the "test of time", the correct way to state it is that "time is running out" and that 'the likelihood of failure increases'. This is because, even when something is *done correctly*, "time" is its enemy, "time" WILL cause it to fail. Now consider when something is *not done correctly* - the "time" between its installation and failure is even less than if it had been installed correctly.

The phrase "passing the test of time" is one of my pet peeves, and far too many home inspectors use that far too often as a reason to ASSUME that what-ever-it-is will 'keep on keeping on' even when they know that what-ever-it-is is done incorrectly/wrong/etc.

I suspect the reason so many home inspector use that phrase is they "don't want to kill the deal" and would rather let their client suffer than the seller or the agent.

Originally Posted by Jerry Peck

That goes right along with what I frequently say: That 'passing' the "test of time" is the wrong way to say it and to look at it. Something does not 'pass' the "test of time", the correct way to state it is that "time is running out" and that 'the likelihood of failure increases'. This is because, even when something is *done correctly*, "time" is its enemy, "time" WILL cause it to fail. Now consider when something is *not done correctly* - the "time" between its installation and failure is even less than if it had been installed correctly.

The phrase "passing the test of time" is one of my pet peeves, and far too many home inspectors use that far too often as a reason to ASSUME that what-ever-it-is will 'keep on keeping on' even when they know that what-ever-it-is is done incorrectly/wrong/etc.

I suspect the reason so many home inspector use that phrase is they "don't want to kill the deal" and would rather let their client suffer than the seller or the agent.

I like the term " passes the test of time", is it appropriate all of the time? No, but it sure does work on many issues we find.

I had a home not long ago that was built in the early 1800's. It had a basement and you could easily see the foundation was constructed from 2'x2, 2'x4' and 2'x6' sections of limestone blocks. The framing in the home was all oak. The beams and joist were oak dimensional lumber. In other words the home was built to last. It was in remarkable condition, the wood framing was so hard and dense that I could hardly make a dent in it with my ice pick (my probe of choice).

The buyer was concerned about the foundation and asked if I thought that the foundation had any major problems because of the age of the house and that concrete was not used for he foundation. I quickly replied that the house is almost 200 years old and it has passed the test of time, and I think it will be here for another 100+ years.

Originally Posted by Scott Patterson

I like the term " passes the test of time", is it appropriate all of the time? No, but it sure does work on many issues we find.

The buyer was concerned about the foundation and asked if I thought that the foundation had any major problems because of the age of the house and that concrete was not used for he foundation. I quickly replied that the house is almost 200 years old and it has passed the test of time, and I think it will be here for another 100+ years.

It has not *yet* "passed the test of time" because it has not *yet* failed, but, given "time" *it will* fail.

A better way to answer questions like that, in my opinion, is to briefly explain the 'why' that is not done any more and, that, yes, it may last another 200 years, but, it 'may not' last another 200 years, it *might* be here another 100 years, but it 'might not' be here another 10-20-50 years - I just do not know how long it will be here.

There is nothing wrong with saying "I don't know" when one does not know.

But that has 'not yet' "passed the test of time", in fact, it is 200 years *closer to failing* than it was originally.

This is because, even when something is *done correctly*, "time" is its enemy, "time" WILL cause it to fail.

I totally disagree with you here, Jerry. Time itself does not affect anything, the conditions do. Deterioration is not a function of time, it can happen quickly or slowly, in some periods and not others, in one home and not the neighbor's.

I think "stands the test of time" is a perfectly reasonable way of looking at something - but one has to be careful how one uses it. I agree that a bathroom vent installed for 11 years may not have seen the range of usage that merits the phrase. Personally, I never use my bathroom fan. Way noisy.

Scott's example is an interesting contrast. Seems like in this instance you'd have to look carefully at the whole structure for very small weaknesses, especially recent change. It sounds very solidly built, but all structures fail at some point, or need restoration - and in a house like that, restoration may cost a pretty penny. All but one small part of the home may stand the test of time, but because the building is not in isolation, eventually the living and/or non-living elements around it will get to something. Deterioration is all about the weakest link.

Am I thinking like a HI yet?

Originally Posted by Kristi Silber

I totally disagree with you here, Jerry. Time itself does not affect anything, the conditions do. Deterioration is not a function of time, it can happen quickly or slowly, in some periods and not others, in one home and not the neighbor's.

"Time" affects the conditions and how those conditions act upon the structure.

More "time" and more conditions are allowed to act upon the structure over a greater period of "time".

Less "time" and the same conditions would not have the same affect upon the structure.

Based on what you stated, a more correct way to state "passed the test of time" would be to state "passed the test of conditions which have acted upon the structure" ... "time" has nothing to do with the conditions which act upon the structure other than to allow more "time" for those conditions to 'do their thing'.

If the conditions acting upon the structure are 'not doing any harm', then it is not "time" which the structure has passed, it is the "conditions" which the structure has passed.

If you take a 200 year old house which has never had to withstand a major hurricane, earthquake, etc., that does not mean that the structure has passed the test of time, it only means that the conditions which have affected the structure were kind to the structure.

Subject that structure to an earthquake, hurricane, etc., and then see if the structure remains undamaged. It is the "conditions" which have affected the structure which it has passed, not "time".

I think the terminology (withstood the test of time) is subjective, there are many old barns which still stand that are over 100 years old and still are in use. But like anything maintenance is a big, big factor.

So yes barns and century homes have withstood the test of time and continue to test time, relative to todays homes which can and do fail without meeting the test of time litmus.

Originally Posted by Jerry Peck

Jack,

That would work okay if the bottom of the vent was enclosed and the exhaust duct was sealed to it to keep any air from discharging (blowing) back into the attic.

The problem with those vents, versus the curved goose neck type, is that the air is simply being blown 'at the flat surface' of the top of the vent. Sure 'some' air will be blown outside through the opening around the vent top, but a lot if it will blow back into the attic. This of spraying a garden hose against the side of the house, some water does spread out along the side of the house, but most of it sprays back at you and if you are too close you will get soaked. Same thing happens with the air, only you don't see it going back into the attic.

Blowing the air against that top is not discharging the exhaust "directly to the outdoors" and does discharge air back into the attic when the code states "shall not discharge into an attic".

I disagree. In the summer the attic air is hot and discharging through the roof vent, which will pull the vent air out with the hot attic air. In the winter the vent air is hotter than the attic air and will rise by itself out the roof vent.

We are to point out defects not to pick and choose which will cause a problem or not. While this is done all over it's lazy and wrong. The idea of the roof always venting to the outside due to stack effect or some other theory is not always the case. In a newer home the attic is more disconnected from the inside than an older home and more insulated. This often allows the attic to remain cold. For example on a cold winter morning that warm moist air can and will freeze on that vent and the surrounding wood. It can also drip down into the insulation. Another scenario is when the wind is blowing against that vent. The wind will enter that vent taking that warm moist bath fan air with it. Blowing it around the attic.

Seems like that screen is a problem. Certainly doesn't seem like an efficient way of venting. I'm not sure how the construction of the vent would facilitate blow-back, though. You've got air flowing up and out, it's protected from wind where it exits the circular part of the vent...hard for me to see how a lot of moist air could be sucked back into the attic unless there are other ventilation issues. BWDIK?

Originally Posted by Jerry Peck

"Time" affects the conditions DISAGREE and how those conditions act upon the structure. AGREE

More "time" and more conditions are allowed to act upon the structure over a greater period of "time". AGREE

Less "time" and the same conditions would not have the same affect upon the structure. AGREE

Based on what you stated, a more correct way to state "passed the test of time" would be to state "passed the test of conditions which have acted upon the structure" ... "time" has nothing to do with the conditions which act upon the structure other than to allow more "time" for those conditions to 'do their thing'.
I should have said, deterioration is not solely a function of time. Of course, over time the conditions have a greater chance to act on the struction.
If the conditions acting upon the structure are 'not doing any harm', then it is not "time" which the structure has passed, it is the "conditions" which the structure has passed. Yes, but that's not how the expression goes!

If you take a 200 year old house which has never had to withstand a major hurricane, earthquake, etc., that does not mean that the structure has passed the test of time, it only means that the conditions which have affected the structure were kind to the structure. I don't think anyone expects old houses to withstand catastrophic events, that's not what the discussion is about. The conditions the structure has withstood, though, may have been enough to destroy other houses. Over the course of 200 years it would be very surprising if the house only had "kind" conditions to deal with.

Subject that structure to an earthquake, hurricane, etc., and then see if the structure remains undamaged. It is the "conditions" which have affected the structure which it has passed, not "time". Exactly.

We're talking about an expression, "the test of time," which I don't think is meant to be taken literally. (Well, that's a tangent to the main discussion [Sorry, Richard!], but anyway...)

Kristi,

Lets start with your closing line at the bottom 'I am not a HI....' and then read what you wrote above it "I dont think its meant to be taken literally'

If you were an HI you would know that the client reads the report and takes every bloody word literally. We cannot stretch the truth or expand on a coloquilism (sp). Mr and Mrs client rely soley on the report when making all decisions.

just the facts ma'am




Kristi wrote "We're talking about an expression, "the test of time," which I don't think is meant to be taken literally. (Well, that's a tangent to the main discussion [Sorry, Richard!], but anyway...)
__________________
I am not an HI, I gather house data for insurance companies...so don't expect me to do/know the things an HI should.

Wind blowing against the one side of the roof creates high pressure as it goes over the ridge it creates low pressure on the other side. Sucks air in one side and out the other side.

Again, only commenting on my region and as I saw today a development where every single new home exhaust fans are exhausted to roof mushroom caps. The only difference up here is that at least the exhaust line is in an insulated sleeve. And I am not talking a few homes I am talking about hundreds in this particular development and other developments with tract homes.

Other developments are the same, so one must come to the conclusion that the building code is being ignored and the code inspectors are allowing the breach.

Its the same in other developments and has been done this way for years, and contrary to others I am not seeing any effects as a result that are creating unfavorable conditions.