How to Ventilate a Bathroom

  • Transcript

    LESLIE: Hey Tom, do we have some time to jump into the email bag?

    TOM: Absolutely. Let me just do that right now. And here’s one on top.

    LESLIE: Now don’t get in the bag. (Tom chuckles) Just reach in the bag.

    TOM: Alright. Mary Beth is writing us. She lives in Chicago and she says, “My bathroom seems to double as a steam room every time someone takes a shower. We don’t have a fan; just a window. Besides being inconvenient, I’m concerned about mold growing on the condensation-soaked walls. Is there a way to add a bath vent now?”

    LESLIE: Well Mary Beth, you are right to be concerned. The bathroom is a hot spot for mold and mildew growth with the warm temperatures and the lots of lots humidity that taking showers generates. This uncontrolled humidity can cause allergy problems; damage windows, walls, ceilings because it encourages the growth of the mold, any sort of bacteria, dust mites, dry rot. You name it; it can happen.

    To prevent your bathroom from becoming a petri dish, you need proper ventilation. And you know what’s happening today? Newer homes may, but don’t always, include bathroom ventilators. And surprisingly, in some areas of the country, builders are not actually required to install a bath fan if the bathroom has a window.

    TOM: Well you know, as balmy as Chicago is, I can’t imagine why it’s a problem to open that winter all winter long when you’re taking a shower. (chuckles)

    LESLIE: But you know what? Even if you open that window, there’s no saying that it’s going to actually suck the moisture out.

    TOM: That’s a good point.

    LESLIE: It’s just an open window.

    TOM: Well you know, there are a number of different kinds of fans that can do the job. You have bath fans, you have remote fans, and you have energy or heat-recovery ventilators. Here’s some of the differences. Bath fans are installed directly to the bathroom. They’re usually on the ceiling and they take the moisture to the outside via a duct.

    Also, you have remote fans. Now these are also known as multi-port ventilators. I like these because they’re mounted elsewhere in the building, such as in the attic, and they use ducts that are connected from the ventilator to the bathroom to draw the moist air out. The nice thing about a multi-port ventilator is that they’re very quiet because the fan is not in the bathroom; the fan is somewhere else in the building.

    Last, it’s really important that the fans be vented properly. One of the most common mistakes that builders make is to vent these fans into the attic. And what does that do? It dumps all the moisture into the attic; exactly where you don’t want it to be because that moisture in the attic is going to get your insulation wet and that means it’s not really going to insulate very well.

    Mary Beth, thanks so much for writing us at

    If you have a question or a comment about your home improvement project, you can simply write us to

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