Why Installing An Exhaust Fan Is Necessary – On the House

Why Installing An Exhaust Fan Is Necessary

By on July 13, 2015
Bathroom exhaust fan

Sweaty windows, peeling wallpaper, mold covered walls and a musty odor are just a few of the symptoms of a poorly ventilated home. The cloths washer, cloths dryer, shower, wash basin, and stove are just a few of the many sources in the home that produce water vapor. It is an excess of this water vapor that causes the maladies described above.

The most effective method of dealing with excessive moisture in the home is to properly exhaust it to the exterior via an automatic exhaust fan. These fans come in various shapes, sizes and styles which correspond to their specific application and the size of the area in which they are to be used.

Let’s take a bathroom, for example. We use this example because, if you’re like many folks, you’re constantly fighting the mildew battle. This may have a great deal to do with those long, hot showers the teenagers in the family enjoy. When does a teenage know that his shower has been long enough? When there’s no more hot water. Sound familiar.

Seriously, according to my friend, who owns a Boston mold remediation company, the high concentration of water vapor produced by a shower will not only produce a fabulous environment for mildew to prosper, it will peel wallpaper and paint, damage wallboard and can even cause framing members to rot.

Building codes in many parts of the country will only require a vent fan in a bathroom that does not contain an operable window. This fan is required to fully exchange the air five times in the coarse of one hour. We believe that an exhaust fan in the bathroom is a must for every bathroom, window or not!

There are several aspects of installation and operation which will produce maximum fan efficiency. Whenever possible an exhaust fan should be installed at the high point in the ceiling. This applies to rooms with ceilings which are vaulted or contain soffits or drop ceilings. Also, the fan should be centrally located and in close proximity to the shower which is the single biggest source of water vapor in the bathroom.

Having a fan is only part of the equation. Properly exhausting the fan is a major part of its successful operation. Most bath fans consist of a metal housing with a dampered exhaust port. Rigid or flexible plastic or metal pipe should attach to the exhaust port and terminate at a jack located on the roof or, in some cases, at an exterior wall. The ducting should be secured to the housing and jack with at least one screw and thoroughly wrapped with duct tape. An exhaust fan should NEVER be discharged into an attic or crawl space. This could result in major damage within these areas.

You may already have an exhaust fan in your bathroom and find that it isn’t doing an adequate job. This may be due to a variety of reasons. One of the most prevalent reasons is lack of use. The fan exists, but no one uses it. Often the fan is switched independent of lighting for the space and is unknowingly not switched on or purposefully because it is too noisy. Some have even gone so far as to disconnect or unplug the fan motor from within the housing. One way to ensure that the fan is used is to tie the electrical for the fan and the lighting together. This can be done at the switch or in attic space. If you are not familiar with electrical work this is a task which is best left to the professional electrician.

Even when the fan is operating properly it still may not be strong enough to adequately exhaust all of the water vapor. This most assuredly has to do with the fan’s power. Fans are rated by the cubic feet per minute (cfm). For example, a 50 cfm fan will move 50 cubic feet of air per minute. An 80 cfm fan is stronger than one rated at 70 cfm. To determine the size of the fan needed for your bathroom the Home Ventilating Institute suggests the following formula. Take the area of the bathroom and multiply it by 1.1 (assuming an eight foot ceiling). For example, a six-foot by eight-foot bathroom would require a fan with a rating of 53 cfm (6 x 8 x 1.1 = 52.8). Remember, this is the minimum recommended size. It never hurts to spend the few extra dollars for a more powerful model. Installation work and cost are generally the same.

One objection that many people have to bath fans is the amount of noise which they emit. Just as fans are rated for capacity of air they move, they are also rated for the sound level. The sound level rating is expressed in “sones”. Therefore, if your fan is too loud you can replace it with a more quiet, lower sone model. Low sound level fans will emit approximately two to three sones, while less quiet models will emit more than five sones.

Another factor which will influence fan performance is cleaning and maintenance. Periodically vacuum the fan blades or turbine and housing. A drop of machine oil at the aperture will keep it running smoothly.

Good household ventilation means ducting the cloths dryer to the exterior, and exhaust fans in all bathrooms, the kitchen and the laundry.


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