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Recommendations for range hood and bath fan venting in soffit?

Kail Zuschlag | Posted in Energy Efficiency and Durability on

I am building a home in climate zone C4 and am trying my best to limit penetrations in the metal roof. I have been thinking of trying to vent both a bath fan and range hood fan out my roof soffits. I am also planning on using continuous soffit vents. Does anyone have any advice or do’s and don’ts around this?

I was thinking of stoping my continuous soffit vents for the 2′ truss bay that I install the exhaust vents in. Am I thinking of this right? Or is there a better method?

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  1. GBA Editor
    Martin Holladay | | #1

    Soffits are not a good place to install vent terminations from bathroom or kitchen exhaust fans, for several reasons. The main reason is that the humid air that exits from these terminations can be drawn into your soffit vents, adding moisture to your cathedral ceiling assembly or attic.

    A secondary reason is that the kitchen exhaust is often greasy, and this type of termination can stain your soffit.

    A third reason is that (at least in cold climates) unsightly icicles can grow on these terminations in winter.

    A fourth reason is that it's hard to find a high-quality termination with an effective backdraft damper for soffit terminations.

    The best place to terminate your range hood fan duct is at a wall termination. If this is impossible, the second best place to terminate it is at your attic gable. If you have a hipped roof without a gable, you may need to terminate above the roof.

    The best place to terminate your bath exhaust fan is usually at an attic gable or a wall. Again, if you have a hipped room, you'll need to terminate this duct above your roof.

    For more information, see Bathroom Exhaust Fans.

  2. Kail Zuschlag | | #2

    Martin- Thank you for the advice. I have a hipped gable on one side of the house and my other gable end is a long distance off.

    If I where to come up from a range hood and 90 out the wall I would be exhausting it through the wall but pretty close to my soffit, Is this a bad Idea? Should I just go straight up and through my new metal roof?

    The bath fan is a long distance from the gable end as well. Would it work to run this through my ceiling and to the exterior wall then 90 down into the wall a few feet and then 90 out the wall? Is this too complicated? Should I just take it straight up through the roof as well?

    How far is too far to run a duct to exhaust a range hood or bath fan?

    Thanks for the advice.

  3. GBA Editor
    Martin Holladay | | #3

    Short ducts are always better than long ducts.

    Terminating your kitchen duct in the wall near the soffit is better than terminating in the soffit. You should terminate there or through the roof.

    It sounds like your best bet with your bath duct is to go through the roof.

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