Bath fan exhaust into attic space

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goldstar

goldstar

Senior Member
Location
New Jersey
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Electrical Contractor
I'm working at a housing project that was built in 1978. There are three floors in each building and in every case the bath fans on the first and second floors are vented to the outside of the building. On the third floor, in all cases, the bath fans are vented into the attic spaces. There are three sections to each building separated by a demising wall that run from the first floor to the attic roof. In no cases are there any gables, ridge vents or roof ventilator fans. The only outside air comes from the roof eaves.

My question is, was it ever an acceptable practice to vent bathroom air and moisture into attic spaces ? I contacted the NJ Div of Codes and Standards who basically referred me to the local AHJ for his opinion. I'm hesitant to contact him because I'm sub-contracting for another contractor on this job. It should be his place to make that call. I was just curious to know if any of you had an opinion on this. Thanks.
 
That sounds like somebody else's problem. I've seen it plenty of times myself. Right up there with venting the dryer into the unfinished basement smh


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ADub said:
That sounds like somebody else's problem. I've seen it plenty of times myself. Right up there with venting the dryer into the unfinished basement smh
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That's basically what the DCA told me but i would hate to see someone get sick claiming it was due to mold and the guys in haz-mat suits show up because we didn't vent it properly. It's been like this since 1978 and we didn't notice any mold in the one section we checked.
 
goldstar said:
That's basically what the DCA told me but i would hate to see someone get sick claiming it was due to mold and the guys in haz-mat suits show up because we didn't vent it properly. It's been like this since 1978 and we didn't notice any mold in the one section we checked.
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I think you should do whatever makes you feel good but personally I feel like the lack of attic ventilation is a bigger issue than the fan. That being said I don't think you'd have a hard time convincing the customer to pay you to vent it properly, I'd probably even do it if it were my house.


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ADub said:
I think you should do whatever makes you feel good but personally I feel like the lack of attic ventilation is a bigger issue than the fan. That being said I don't think you'd have a hard time convincing the customer to pay you to vent it properly, I'd probably even do it if it were my house.
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I appreciate your opinion but it's a little more complicated than just asking the customer if they want it vented. There are 72 units in this complex of which 24 are on the top floors. The company I'm working for contracted to replace the fans only and not any venting. It was their impression, at the time of the contract signing, that vents were existing. I can go on and on but you get the drift. The long and short of it is not what is right but who is paying for it.
 
goldstar said:
I appreciate your opinion but it's a little more complicated than just asking the customer if they want it vented. There are 72 units in this complex of which 24 are on the top floors. The company I'm working for contracted to replace the fans only and not any venting. It was their impression, at the time of the contract signing, that vents were existing. I can go on and on but you get the drift. The long and short of it is not what is right but who is paying for it.
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Are you getting inspections on this work?
 
goldstar said:
My question is, was it ever an acceptable practice to vent bathroom air and moisture into attic spaces ?
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I actually think that it just got overlooked in the early days.

Ventilation is in the mechanical code and not electrical. You may or may not even be allowed to vent these fans, it may be that a mechanical contractor (HVAC) will be needed.
 
growler said:
I actually think that it just got overlooked in the early days.

Ventilation is in the mechanical code and not electrical. You may or may not even be allowed to vent these fans, it may be that a mechanical contractor (HVAC) will be needed.
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That would be the case here if the rules are followed.
 
Yes, venting to the attic was done in the past. It hasnt been allowed for some time now. No idea of 1978 codes... better question is "does replacing an existing fan require the ductwork/venting(or lack thereof) be brought up to current code?"
 
I imagine that if you are replacing the bath fans then the system must be brought up to code. Whose responsible for venting may be in question, but the install probably will not pass if not complete.

IBC

501.3 Exhaust discharge.
The air removed by every mechanical exhaust system shall be discharged outdoors at a point where it will not cause a nuisance and not less than the distances specified in Section 501.3.1. The air shall be discharged to a location from which it cannot again be readily drawn in by a ventilating system. Air shall not be exhausted into an attic or crawl space.

IRC

M1501.1 Outdoor discharge.
The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1506.2. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.
 
jumper said:
I imagine that if you are replacing the bath fans then the system must be brought up to code. Whose responsible for venting may be in question, but the install probably will not pass if not complete.
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I think that is very reasonable and I agree.


I look at it this way, I might add a branch circuit to a panel that is not up to code as far as say the GES without fixing the GES but for sure if I change the panel I would be bringing the GES up to date.
 
I'm not sure of when the code changed, but when I started in this trade back in 1992 an exhaust fan could be vented into an attic, at least 3 feet so as to be above insulation.

Somewhere in the early 2000s they were required to be extended to "near" a roof vent.

Now, as jumper showed, all bath fan exhaust must leave the building.
 
Years ago we almost always ran vents into the attic space, unless it wasn't the top floor.

About 10-12 years ago I felt that the humidity should be brought outdoors instead of into the attic, there is no one enforcing codes on this around here but I also understood that to be what is code where it is being enforced, so I started to vent those applications out the roof, and have had nothing but problems with it.

If you don't maintain a slope on ducting toward the bath fan you will have water pool up in your duct, if it is not well supported flex duct it will sag and make a "trap" and then the fan doesn't move any air.

If you do maintain a slope any condensation that forms in the duct runs back to the fan and drips on the floor in the room below - owners don't like that. It is worst in cold weather when condensation freezes on the duct wall and when you run the fan the warm air being exhausted melts it, that is when you get the most water all in a short time. Insulated duct helps but doesn't prevent this altogether.

I have done many new homes in rural areas, the wind does blow in cities and towns but is often even more severe out in the open where there is little there to slow it down. Even with a backdraft damper on the fan as well as the roof cap, cold air still falls out of the bath fans on cold windy days, owners don't like that either.

I tried to do my own house "the right way". After about 10 years I finally pulled the duct from the roof cap and am now venting into the attic, and I know many of past customers have done the same at some point.
 
JFletcher said:
Yes, venting to the attic was done in the past. It hasnt been allowed for some time now. No idea of 1978 codes... better question is "does replacing an existing fan require the ductwork/venting(or lack thereof) be brought up to current code?"
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This was basically the response I got from a State official. If you're just replacing the fan, then replace the fan and someone else has to do the duct work. My thought was to buy a 25' aluminum flex hose, cut it in half, attach one end of those halves to each exhaust fan in the apartment bathrooms and leave the ends in the attic pointed toward the eave. The maintenance people or an mechanical contractor can come along later and cut a vent into the eave, pull the hose through and attach it.

Thank you all for your responses.
 
A lot of the problems, including moisture trapping as mentioned, can be caused it at least made worse by the use of flex duct instead of hard duct.
Unfortunately flex is so much easier to work with.
 
GoldDigger said:
A lot of the problems, including moisture trapping as mentioned, can be caused it at least made worse by the use of flex duct instead of hard duct.
Unfortunately flex is so much easier to work with.
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Flex also affects the air flow rate more than hard duct.

Here's an interesting hypothetical: say the OP is responsible for just the fans, so he installs standard 50-60cfm fans. Inspection fails (exhaust vented to attic) but it's mechanical, not electrical. So an HVAC co puts in new ductwork to the eaves. Ductwork is up to code, however the inspection fails again because the airflow rate is not the minimum 50 cfm intermittent. Who is now on the hook for the job, the EC who put in the fans, or the HVAC who did the ductwork?
 
JFletcher said:
Flex also affects the air flow rate more than hard duct.

Here's an interesting hypothetical: say the OP is responsible for just the fans, so he installs standard 50-60cfm fans. Inspection fails (exhaust vented to attic) but it's mechanical, not electrical. So an HVAC co puts in new ductwork to the eaves. Ductwork is up to code, however the inspection fails again because the airflow rate is not the minimum 50 cfm intermittent. Who is now on the hook for the job, the EC who put in the fans, or the HVAC who did the ductwork?
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If the fan can move the right amount of air then it has to be the duct design that cuts down the air flow or even lack of make up air.

Things that can improve air flow - less length, less elbows, rigid instead of flex duct, larger duct size. If you need flex, long length, extra elbows then larger duct size becomes more necessary as compensation .
 
JFletcher said:
Flex also affects the air flow rate more than hard duct.

Here's an interesting hypothetical: say the OP is responsible for just the fans, so he installs standard 50-60cfm fans. Inspection fails (exhaust vented to attic) but it's mechanical, not electrical. So an HVAC co puts in new ductwork to the eaves. Ductwork is up to code, however the inspection fails again because the airflow rate is not the minimum 50 cfm intermittent. Who is now on the hook for the job, the EC who put in the fans, or the HVAC who did the ductwork?
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That's an interesting question. Assuming that the fan is like the ones I quickly scanned at Lowe's and Home Depot, their typical output is in the neighborhood of 100 CFM with 4" duct. The rating is with 0.1" WC pressure drop. If I were the construction official, I'd like to see calcs from someone that the duct as designed would allow the minimum exhaust flow to be achieved. Probably on the HVAC guy to provide.
 
Had an install of a dryer in an interior laundry area in a large house. The closest vent route to the outside was over 30 feet. Most of the duct ended up 6" and the inspector asked to see calculations that the particular dryer was rated for the .5" water column pressure drop that the duct run calculated out to be. It was. :)

PS: Unfortunately the guy who installed the duct mis-set the exhaust hood and rain water came in, puddled in the middle of the horizontal run and leaked through the ceiling board if the dryer was not run often enough. Not my problem.
 
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