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My contractor wants to vent our bathroom exhaust fan by connecting tubing to our attic turbine vent (aka whirly bird) to exhaust it to the outside instead of plumbing it to the outside through the roof. Is this up to CA codes? This seems like a short cut.

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What is a whirly bird? – Rory Alsop Feb 3 '13 at 11:17
@RoryAlsop; a whirly bird is a circular roof vent that spins. @ker: This is definitely a shortcut. My understanding of proper vent installation is that it should be either through the roof or wall. Not through the eaves (moisture gets pulled back in through vents). Do you cover your 'birds during the winter? If so, you're trapping moisture in your attic. – Brad Bruce Feb 3 '13 at 15:07
Depending on the connection detail, it is either reducing the vent's free area, or a fair part of the moisture could still enter the attic when the vanes are not turning. While it's better than just dumping straight into the attic (a much too common practice), it's still not right. – bcworkz Feb 3 '13 at 20:12
@RoryAlsop - a "whirlybird" is properly known as a "turbine vent". – Compro01 Feb 4 '13 at 14:57

Your contractor is lazy. The best solution is through the wall (though not near an eave), but if that is not possible, a dedicated vent in the ceiling is necessary.

If there is no wind, dumping the hot moisture-laden air into the whirlybird will just put it back into the attic.

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