Learn why bath fans are key to reducing the risk of mold and mildew growth in your bathroom. Find out how to use them and learn why a bathroom window isn't really a viable substitute for a bath fan.
LESLIE: Well, you might think that there is no way to escape mold and mildew in your bathroom; you know, not with all that moisture that occurs in there. But bath fans go a long way in keeping moist air to a minimum.
And Kevin, you know, cleaning mold and mildew can become a thing of the past with the right ventilation. Correct?
KEVIN: You got that right. Nobody likes cleaning mold and mildew in a bathroom but that job can be made a bit easier if the moisture from a shower or a bathtub is vented out quickly. And you can do that with a properly-sized and properly-installed bathroom fan .
TOM SILVA: Right, bathroom fans are very important. It lessens the chance of moisture that can take hold in the bathroom and mildew can grow and mold will grow. And run the fan longer than you take a shower. What I like to do is I like to put a 60-minute timer in a bathroom so that when you get in the bath and you turn the fan on, it’s going to run for 60 minutes. So when you leave that bathroom, all that warm, moist air is going to be drawn out of the bathroom.
And it’s very important that you don’t vent the bathroom into an attic or through a soffit. That warm, moist air will get collected into the attic under the underside of the cold sheathing and it condenses. It’ll also wet the insulation and make it more inefficient.
KEVIN: So it’s important to get the exhaust outside.
Is it true that some building codes don’t require a bath fan to be installed if there’s a window in a bathroom?
TOM SILVA: Yeah, but that presumes when you get out of the shower you’re going to open up the window in the middle of the winter and let all the cold air in. And more important, you’ve got to remember to close a window when you leave the bathroom. So a bathroom fan is very, very important.
KEVIN: Alright. Well, if you need more information, there are several videos about bathroom fans  on our website at ThisOldHouse.com.
TOM: Guys, I’ve got to tell you that that 60-minute timer would not be enough in my house with my teenagers. (chuckles)
KEVIN: Yeah. You’re right, Tom.
TOM: Tom Silva, Kevin O’Connor, thanks for stopping by The Money Pit.
KEVIN: My pleasure.
LESLIE: Yeah, and you know, speaking of teenagers, they’re a noisy bunch. I mean I’ve been over Tom’s house and that house is noisy all the time. Well, if you’re thinking that a bath fan is going to be noisy like Tom’s kids, they really aren’t. There are so many new models with bath fans out there that are super-duper-duper quiet and you might actually get some peace and quiet from those kids.
TOM: Yeah, probably not. (Leslie chuckles) But that’s why I keep my headphones around; wear them around the house when it gets really, really noisy.
TOM: What?! Can’t hear you!
TOM: Well, for more great tips, you can watch Kevin and Tommy on TV’s This Old House. And This Old House is brought to you by State Farm. Like a good neighbor, State Farm is there.