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No range hood in kitchen: How will that affect the attic above?

Mat R | Posted in General Questions on

My kitchen has a gas stove on an island with no range hood. Above it are three recessed can lights in the ceiling, and an attic space. The attic has fiberglass batt insulation. What will that warm moist air from cooking do, since it isn’t being vented to the outside? How bad is this from an insulation standpoint? Should I be worried about mold and wood rot? How urgent of a problem is this to fix?

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Replies

  1. Expert Member
    Peter Yost | | #1

    Hi Kneewall -

    For every therm of gas you burn (90k Btus or so), a pint (about a pound) of water is generated. Then there is the water evaporating from whatever you are cooking (take a look at this GBA resource: https://www.greenbuildingadvisor.com/article/moisture-sources-relative-humidity-and-mold).

    So, it is hard to say what the exact impact of this moisture load will be in your home/attic, but it is a load that needs management.

    You did not mention if you can manage with a downdraft hood ? I would think of this as a last resort because they need to be so powerful (See GBA resource: https://www.greenbuildingadvisor.com/article/hvac-equipment-can-overpower-wind-and-stack-effect).

  2. GBA Editor
    Martin Holladay | | #2

    Kneewall,
    The amount of potential damage depends on whether the recessed cans are leaky or not. (Hint: Most are.) If a weatherization contractor has provided an airtight cap over your recessed cans, you may not have any damage. If the recessed cans are typical, they leak a lot of air -- and a lot of damage is possible, especially if you live in a cold climate.

    We need more information:

    1. Where do you live?

    2. Do you have an attic above your kitchen, or a cathedral ceiling?

    3. If you have an attic, can you get up there to see what's going on?

    1. Mat R | | #3

      1. I live in central Indiana.

      2. It's a kneewall attic.

      3. There's an access door that makes it very easy to get in there.

      I don't think there's any sort of sealing around the lights. I haven't looked closely at them lately, but I don't remember seeing any sort of box or cover over the light fixtures.

  3. GBA Editor
    Martin Holladay | | #4

    Kneewall,
    For more information on what to do with your recessed can lights, see this article: "Recessed can lights."

    If you don't solve the air leakage problem, at least poke your head in the attic every now and then to see if you have any mold, moisture problems, or rot.

    1. Mat R | | #5

      I will definitely take that advice to heart, thank you. Is there any danger that the moist air will just collect inside the air sealed light housing and cause other problems?

      1. GBA Editor
        Martin Holladay | | #6

        Kneewall,
        Interior air is warm and moist, all winter long. That's normal. As long as this interior air doesn't contact a cold surface, you won't have any condensation. So the idea is to keep your recessed lights (assuming you don't remove them -- after all, they aren't recommended) warm enough to avoid condensation.

        If all of the metal components of the recessed fixtures are warm, you won't have condensation.

        That said, air leakage is also an issue. So, assuming you want to keep your recessed lights, you need to (a) seal air leaks, and (b) keep the fixtures warm by installing insulation above them. These steps need to be accomplished without the risk of overheating, so follow the directions in my article to do this work safely.

  4. Expert Member
    Peter Engle | | #7

    Or replace the recessed lights with sealed, IC rated LED lighting fixtures and complete the air seal for the kitchen ceiling.

    Your risk also depends on your cooking style. If you use your stove occasionally to cook a quick meal for one or two people, there is little risk. If you have a pot of pasta water always simmering on the stove for a family of 6, your risk is higher.

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