Comments on: Don’t Vent Bath Fans to the Attic! https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/ Building science knowledge, HVAC design, & fun Tue, 07 May 2024 22:09:45 +0000 hourly 1 https://wordpress.org/?v=6.6.2 By: Robert Adams https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37614 Sat, 24 Feb 2024 03:30:38 +0000 https://www.energyvanguard.com/?p=8814#comment-37614 In reply to John.

Not sure what code was then but when it comes to paying off inspectors there is no reason to.. They are not there to inspect and make sure houses are built to code. They are there as part of the city revenue collection team. And the massive number of extremely poorly built houses these days is evidence to back that up.
Permits and inspections will not have any teeth and never mean anything until they are properly handled. That means when the inspector signs off on it and says it was done properly the builder is off the hook and now the onus is on the inspector as he assured it was done right and now he “owns” it. If they city feels their inspections are that important they need to take responsibility for their approvals.

Until that change happens it’s all just a muddy mess of revenue collecting under the guise of making sure houses are built correctly.
Right now if a builder does X wrong and it was signed off the builder says hey the city signed off on it but the builder is on the hook even though it was approved by the city inspector. What should happen is if it was signed off by the inspector the city should be on the hook for any damages. But for now it’s all a charade.

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By: John https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37610 Fri, 23 Feb 2024 21:49:48 +0000 https://www.energyvanguard.com/?p=8814#comment-37610 I have a 1974 in Denver. Of the 3 bathrooms only one has a vent. The other two have windows which apparently made it okay to not have a vent. We are forever fighting excess humidity in the main bathroom and now just leave the window open for ~30m after showers even if it is sub-freezing outside.
We also have a 1984 condo. The “vent” in the bathroom is a fan without any kind of ducting. Just a fan in the ceiling to swirl the humidity around. I have no idea how this could be code in 1984 or someone just paid the “inspector” to overlook it.

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By: Steve Robinson https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37168 Thu, 01 Feb 2024 13:07:03 +0000 https://www.energyvanguard.com/?p=8814#comment-37168 As a now retired architect in Ohio, I have enjoyed your articles Allison over the years and learned a good deal. Proper venting of bathroom, stove, and dryer vents has always been a priority for me in my homes and design projects. About a year ago, I helped a good friend and retired electrician clean out one of his bath exhaust vents that did vent to the outside end wall, and we found massive amounts of bird nesting in there. We made sure to install a new and proper cage on the outside! I do want to make one note regarding this article and all the photos of attic vents. Some of those vents may be in half baths (“powder rooms”) and in most cases probably don’t demand a vent to the outside since it’s only exhausting foul air (and that occasionally). I have one such vent in my house. The half bath is rarely used, and the vent even more rarely; essentially, the vent is pushing very low moisture air into the attic during the conditioned seasons and slightly higher moisture content in spring and fall. Plus in my case the attic is very large, well ventilated, and over the garage. Ideally though, I may still eventually run that duct to the exterior.

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By: Mark Johnson https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37153 Wed, 31 Jan 2024 02:11:07 +0000 https://www.energyvanguard.com/?p=8814#comment-37153 I wish someone would report this type of thing using dewpoint and temperature measurements, and case studies of harm being caused. I live near Houston, my attic is vented to outside, and my hypothesis is the dewpoint of bathroom air is generally LOWER than the outdoors. That would seem to argue a remote chance of mold from this source. But I have not studied this as much as professionals.

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By: Stacy Long https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37152 Wed, 31 Jan 2024 02:00:14 +0000 https://www.energyvanguard.com/?p=8814#comment-37152 In reply to Graham Davis.

This must be one of the benefits of manufacturing housing. There’s no attic, just a 2×6 framing to connect the vaulted ceiling to the roof. The bath vent termination is easily seen from the outside.( I realize that also means I’m going to have difficulty enhancing the R15 insulation there) I have also yet to find a particularly good damper (a skinny foam one was provided and is better than nothing, but the cape cod ones recommended here wouldn’t fit the small space).

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By: Bill Cowhig https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37150 Tue, 30 Jan 2024 23:32:28 +0000 https://www.energyvanguard.com/?p=8814#comment-37150 Allison,

Our home was built in 1997. I call it “contractor grade.” When I took a look at the three exhaust vents, however, I found that one made it all the way to the outside (Dryer vent — runs through the crawl space; that one is good as I can clean out the accumulate “lint” periodically), the second and third exhausts actually had exhaust vent openings through the exterior end walls to the outside, good.

Not exactly. Both of them had come loose and dropped off their penetrations, and were just laying in the insulation. The problem, then as now, they are on opposite ends of the attic, and getting to them is going to be “difficult.” One is way down low on the end wall, where the roofline slopes almost to the sofit, so I will have to crawl through insulation to get to that one. The other one is beyond a kind of attic end wall that is at the separation to the bonus room over the garage. I will have to make some kind of a door through that wall, just to get to exhaust hole. It has been on my todo list for a while now.

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By: Robert Adams https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37149 Tue, 30 Jan 2024 23:16:14 +0000 https://www.energyvanguard.com/?p=8814#comment-37149 While I agree100% that they should terminate outside the roof… I have to say that here in North TX the vast majority of houses here have them dumping into the attic. And of those houses I have never ever seen any of the possible issues with the air going up in the attic. It’s a climate difference. It’s not ideal but here it’s not really an issue. That said With it not going through the roof you have one less puncture in the roof that can and will leak in the future…

Seems 140* air in the attic doesn’t have an issue with 70*-80* moist air from the house going into it. No shortage of attic air flow here.

Now the better halfs moms 80s condo in Ohio… I think the exhaust fans are just for noise and decoration. I see no exit vents anywhere and none in the attic. Her spare bathroom does get full of cigarette smoke from the unit next to it. I have been tempted to just seal off that vent fan since it doesn’t go anywhere and to keep the stench out of it. There is no access to properly run a vent hose anywhere so properly fixing it is a moot point.

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By: Graham Davis https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37147 Tue, 30 Jan 2024 22:02:52 +0000 https://www.energyvanguard.com/?p=8814#comment-37147 Another common problem we often see is an exhaust duct pointed in an upper roof vent. This works fine if the only air flow is stack effect. However, when the wind blows on the side of the roof where the vents are located, that roof plane is pressurized making the attic air negative with respect to the exterior and the roof vent will suck anything coming out of the duct right back into the attic. When using this practice, we encourage builders to seal the exhaust penetration to the roof sheathing to prevent this.

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By: Jim Breitenbach https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37146 Tue, 30 Jan 2024 21:00:57 +0000 https://www.energyvanguard.com/?p=8814#comment-37146 Allison,
While I was renovating my daughter’s 1980’s condo six years ago, I found the following.
The half bath exhaust fan damper was held closed by a drywall screw. Upon removing the half bath ceiling, we found that the electrician had layed all his runs from the electric panel across the 4 inch plastic spiral duct from the exhaust fan. The duct was as flat as a pancake. Just past the flat duct the duct from the second floor bath tied into the half bath duct and the exhaust from both baths ran in a single duct through the ceiling to outside.
The ductwork was repaired, but couldn’t put in another run. So guess where some of the exhausted air ends up. Yep in the other bathroom.

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By: Allison Bailes https://www.energyvanguard.com/blog/dont-vent-bath-fans-to-the-attic/#comment-37145 Tue, 30 Jan 2024 19:22:53 +0000 https://www.energyvanguard.com/?p=8814#comment-37145 In reply to David Power.

David: I’m glad you found that and had it fixed!

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