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Old 12-23-2010, 06:58 PM   #16
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bathroom exhaust fan code


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Originally Posted by oleguy74 View Post
there is a metal flex tube/duct from fan to vent to outside air.the flapper keeps outside air from comming back into house.unless this duct comes off,no exch to attic.
They were talking about a soffit vented bath fan. The moisture laden air is expelled next to the soffit vent which takes that moisture laden air into the attic. The flapper just keeps the cold exterior air from being drawn into the ductwork after the dryer stops. That is if the flappers are cleaned on a regular basis and don't keep the flappers open with caked lint.
The issue is seasonal in the colder climates as convection is limited in the cooler seasons.
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Old 12-23-2010, 07:06 PM   #17
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if done to code NO.you need a metal duct from fan to sofit vent.unless duct comes off no outside air to attic.
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Old 12-24-2010, 01:41 AM   #18
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This has been a code change in the last several years. The 2000 IRC permitted you to discharge a bath fan into a ventilated attic. More recent editions require it to discharge to the outdoors. Nothing requires that it go through the roof. Personally I see penetrating the roof as a last resort, and feel that a soffit penetration or a gable penetration is more desirable. The aforementioned soffit penetration/damper kits are really slick, and are very similar to a dryer vent termination. Code doesn't require a metal pipe that I'm aware of, and flexible vents are fine.
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Old 12-26-2010, 06:10 PM   #19
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code does require the duct.other wise it discharges directly to attic...code violation.
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Old 12-26-2010, 06:59 PM   #20
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This has been a code change in the last several years. The 2000 IRC permitted you to discharge a bath fan into a ventilated attic. More recent editions require it to discharge to the outdoors. Nothing requires that it go through the roof. Personally I see penetrating the roof as a last resort, and feel that a soffit penetration or a gable penetration is more desirable. The aforementioned soffit penetration/damper kits are really slick, and are very similar to a dryer vent termination. Code doesn't require a metal pipe that I'm aware of, and flexible vents are fine.
Can you please recommend a soffit ventilation kit?
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Old 12-26-2010, 07:24 PM   #21
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Real world, the problems with soffit vents as compared with gable, roof and sidewall vents usually involve installation issues, including:

1) They often involve longer runs that through-roof vents.

2) By their nature, they involve horizontal runs.

3) They are more often run in flexible ducts.

4) These three conditions mean that they are usually much more subject to low spots and other causes of condensation problems.



5) Because they are on the attic floor, and usually in flexible duct, they are considerably more likely to experience mechanical damage from foot traffic and stored household goods:



6) Especially at roofs with a slope lower than 4/12, it is often somewhere between difficult and impossible to correctly install the duct and terminations, during my inspections this is a very common location at which to find disconnected or damaged ducting:



The bottom line is that assuming a properly pitched vent is run in properly insulated hard pipe and correctly and permanently connected to a properly installed termination, and as long as the attic is not negatively pressurized (for example by a powered attic ventilation fan) and exhaust air is not drawn back in through the soffit vents, then a soffit vent is fine - but at least in my area (Chicago) the chances of finding such an installation are pretty slim.
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Old 12-27-2010, 10:10 AM   #22
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Old 12-27-2010, 04:21 PM   #23
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Those pictures are clearly excessive, some aren't even of the description that is printed on it. For example, the excessive bends and twists in the first picture is not what flexible duct is "prone to do", that was installed in a poorly way. That is VERY easy to fix and make right.

In the second picture, it's not foot traffic or stored material that did that to the duct, it's the person who installed the high hat, he specifically separated the duct to install the light where it looked correct from down below, the duct now needs to be reconnected or rerouted.

In the third picture, the good money says that the installer just ran the duct to the soffit, they didn't cut the soffit out and install a proper soffit vent.
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Old 12-27-2010, 06:23 PM   #24
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Those pictures are clearly excessive, some aren't even of the description that is printed on it. For example, the excessive bends and twists in the first picture is not what flexible duct is "prone to do", that was installed in a poorly way. That is VERY easy to fix and make right.
Well sure, that's an extreme case (people tend to take the point of a really dramatic, and hopefully amusing, example), but I see many examples of flex duct installed with dips and sections with reverse pitch - its just the nature of the beast.

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Originally Posted by General View Post
In the second picture, it's not foot traffic or stored material that did that to the duct, it's the person who installed the high hat, he specifically separated the duct to install the light where it looked correct from down below, the duct now needs to be reconnected or rerouted.
The duct and the light were installed as part of the same rehab, and the exhaust system was functioning for some time after the install. It was also clear from the condition of parts of the duct not visible in the foreground that the duct was pulled loose when stored possessions were moved around in the attic - they were sitting on top of it when I performed the inspection, pulling it down between joists.

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Originally Posted by General View Post
In the third picture, the good money says that the installer just ran the duct to the soffit, they didn't cut the soffit out and install a proper soffit vent.
I see this frequently - duct disconnected for the termination, when an attempt has been made to retrofit to such an exhaust point, especially at the eave of a low pitched roof where there is limited working space

--------------

Look... I inspect property for a living. I know based on daily experience what is likely to work. and what is likely to fail.

I listed the conditions required for a soffit vent to work reliably.

I see failed attempts to meet them more often that I see successful ones.
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Old 12-27-2010, 06:28 PM   #25
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Look... I inspect property for a living.
That's all ya had to say...
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Old 12-27-2010, 09:33 PM   #26
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M1507.1 General. Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section. http://publicecodes.citation.com/ico..._15_sec007.htm

GBR, I read this as "if you vent the bathroom, it must be to the outdoor". Further north, houses are tight (at least they are supposed to be), and I need a second switch on my main floor, so I can turn on my bathroom fan for house ventilation. But in TN, I am not so sure that is the case.
Does this answer your question?
R303.3 Bathrooms. Bathrooms, water closet compartments and other similar rooms shall be provided with aggregate glazing area in windows of not less than 3 square feet (0.3 m2), one-half of which must be openable.

Exception: The glazed areas shall not be required where artificial light and a mechanical ventilation system are provided. The minimum ventilation rates shall be 50 cubic feet per minute (24 L/s) for intermittent ventilation or 20 cubic feet per minute (10 L/s) for continuous ventilation. Ventilation air from the space shall be exhausted directly to the outside. http://publicecodes.citation.com/ico...003_par002.htm


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