There are basically 2 types of exhaust fans to consider in a bathroom. The most common is a ceiling mounted fan where all the fan parts are mounted just above the sheetrock. We try to stick with fans made by Panasonic because they are both quiet and efficient but Broan also makes a good exhaust fan which detects excess moisture automatically. The other type is called an in-line exhaust fan made by Fantech and the difference is that the actual fan housing and motor get mounted up in the attic away from the bathroom so the noise is far less, sometimes inaudible. Both types can more than adequately remove humidity from a bathroom but only if they are left on for about 15-20 minutes after you leave the bathroom. Many people forget to turn on the fan before they start their shower which is going to lead to mildew in no time. Here is the best way to deal with the fan switch scenario. We like to use a switch by Energy Federation Incorporated called a timer delay switch. Turn the switch on and both the lights and the fan will turn on. Turn the switch off and the lights will turn off but the fan will continue to run (user settable up to 60 minutes). The adjustment screw is on the face of the wall switch, but will be behind the cover plate, so once you set it you won't have to think about it again. You can also use a conventional timer switch but unless you get the $40 electronic switch you will be annoyed by the ticking of the basic $18 switch. I suggest spending $40 on the timer delay switch and end all worries. If the fan is quiet enough to begin with then it won’t be an issue when it comes on along with the light every time you enter the bathroom. I would suggest wiring the fan up with the main light you turn on when you enter the room. It is not necessary to connect it to every light in the bathroom.
There are a few other factors to consider such as appearance, air suction (CFM), options such as heater and light. Some fans do not have a light and some have both a light and heat lamp. I stay away from the units that have every option because they seam to be noisy and lower quality units. The inline fans are nice because the round ceiling register is only 6” in diameter and blends in nicely with the ceiling. The register can also be adjusted to allow for different air flows. This would be important if you had a large bathroom with two or more registers. When you have multiple registers you sometimes need to adjust them individually so they don’t whistle or make noise. This is because the ducts tend to be different lengths leading to the registers and unbalanced air flow can lead to excess noise.
Whatever fan you choose you need to make sure that the exhaust is vented directly to the outdoors and not into the attic space. This could lead to excess humidity in the attic which translates into mold and condensation. Many novices use the flexible white dryer vent which is a no-no. It is critical to use insulated ductwork in the attic because the warm moist air that is being exhausted could condense in cold un-insulated ductwork and turn into water which will end up finding its way back into the bathroom in the form of drips.
Here are a few final tips to improve the performance of your fan. Check the gap under the bathroom door. There should be about ½” space under the door to allow air from the rest of the house to enter the bathroom. If there isn’t adequate air entering the bathroom from the rest of the house then the fan will not be able to pull the moist air out of the bathroom. This is called make-up air and is often overlooked. Also keep the register clean and free of dust. The sign of a properly operating fan will be an accumulation of dust around the register. You can remove the register and rinse it off or vacuum it off. If you are not sure how well your fan is working try one of these two tricks. Take a single sheet of toilet paper and hold it up to the register. If the fan is working properly it will hold the tissue tight against the grille when you let go. You can also puff some baby powder into the air next to the register and a good fan will instantly suck all the powder out of the air.
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