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How to Install a Bathroom Fan

November 8th, 2009

bathroom-fan-install.jpgOkay, so now you have a bathroom fan — but how do you install it? The first step is to choose a location in the ceiling. Since a fan pulls away odors as well as humidity, the best approach is to place it midway between the shower and bathtub area and the toilet. This allows the fan to do its job with maximum efficiency.

If you have a steam shower, you’ll need a separate fan to handle all the humidity. The principle behind the steam shower, after all, is that the glass doors seal up, and so much moisture is pumped in that it literally becomes an indoor greenhouse; it’s like a human hydroponics experiment in the master bath suite. Though you want all the steam trapped in there for the duration of your shower, you want to make sure it evacuates as soon as you’re done. Otherwise, your bathroom walls are going to resemble a Chia Pet from all the things that start to sprout on them.

A separate exhaust fan dedicated to just the steam shower is essential. In large bathrooms, the toilet is sometimes enclosed in a compartment, which is the classic water closet or WC. In this case, you would also want an additional fan located in that compartment because even though the room may not generate any steam, it will generate odors that won’t air out on their own.

Besides positioning the bathroom fans, the other half of the problem is properly fitting the vent tubing that attaches to the fan. This has to be connected outside, so that moisture can be removed from the house completely. The vent will be covered with an exterior flap, similar to the one that you find on the outside cover of a clothes dryer.

Sometimes homeowners who don’t know better and contractors who want to cut corners try to vent the fan directly up and into the attic. The humidity literally blasts up there and condenses, causing just as much damage as it would have done if it had stayed in the bathroom in the first place. This is especially true in areas with cold winters, where the condensation effect is even more pronounced. This constant dampness creates a potential breeding ground for mold and mildew. Worse, the water that accumulates on the underside of the roof can do real structural damage over time.

One thing to worry about (again in cold climates) is condensation within the tube. In all cases the tube should be rigid metal, which looks something like a stovepipe. Flexible hose that you find on a dryer is simply not adequate for this sort of application because it won’t hold up. But metal tubing presents some challenges of its own. Often people will install fans in a ceiling, then immediately attach a pipe that rises straight up above the insulated space. This has some advantages, because the short run of tubing means that the fan will move air more efficiently. On the flip side, moisture can condense inside the pipe, and then it begins dripping back into the tubing and back through the fan and right onto the bathroom floor. As fast as you can pull moisture from the room, it seems, it rains right back down. Not only is this fairly revolting to anyone standing beneath it, you also run the risk of damaging the bathroom fan motor since it was surely not designed to be saturated.

The solution to this lies in some clever placement of the piping. Where it attaches to the fan, the tubing should be connected to a 90-degree elbow pipe and should run straight for a good two or three feet along the backside of the plaster or drywall ceiling. This should be covered with insulation to protect the metal from extreme cold, which will buffer the cooling of the humid air in winter. That way, the moisture in it won’t condense all at once. Then, instead of rising with an immediate 90-degree turn upward to vent outward, you gradually raise the pipe up to the roof using two 45-degree elbows. Although moisture will still condense on the inside of the pipe, it won’t be to the same degree. And since it won’t begin condensing until after it passes through the insulation, some 3 feet away from your bathroom fan, water won’t be able to drip back down through the fan.

This article on how to install a bathroom fan was supplied to us by “Plato” from the DigitalPoint forums under a private label rights license.

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