How to Manage Unvented Bathrooms


Vented and Unvented Bathrooms

In many residential structures, there are bathrooms that do not have an exhaust fan or a means of venting the bathroom.  This occurs especially in older homes or in bathrooms that have been added in existing spaces. Venting of a bathroom environment is an important issue.

Why is the bathroom an important room to vent?

Running water, especially hot water, will cause condensation and the build up of moisture within the atmosphere of the bathroom.  In many instances there is a ventilation fan that will draw this moist air out of the room and remove the excess moisture. Without a ventilation fan, this room will start to accumulate moisture within the atmosphere of the bathroom.

Why am I concerned about the accumulation of moisture within the bathroom?

Moisture stimulates and promotes the growth of mold, which is one of the most intrusive and unhealthy conditions that can occur within a living environment.  Mold requires moisture to grow and to thrive. If the air is dry and any moisture accumulation is allowed to evaporate or dry up, mold will not propagate. However, if moist air is allowed to occur and remain within the environment, then the chance of mold growth is increased.  Moist air, caused by running hot or warm water, without ventilation or a drying opportunity, will cause mold to occur and grow.

Based upon this occurrence, excessive moist air should be minimized within any living environment.  We note the term excessive, due to the fact that some degree of moisture is required in the air for health reasons, as well as minimizing the negative drying situations that cause furniture joints to loosen up, or inhabitants within a dry environment to suffer from dry skin, scratchy throats and a myriad of other negative issues.  

How can I minimize accumulation of moisture within my bathroom?

  1. The most efficient method is the use of a ventilation fan that is vented to the outside.  In many contemporary bathrooms, this fan is mounted as a combination fan, light assembly in the ceiling of the bathroom.  There are several primary makes of residential fans on the market. The venting of the moist air to the exterior environment is importance, due to the fact that the simple transfer of the moist air from the bathroom to the attic or basement promotes moisture build up in these areas.  It is always best to vent to the exterior atmosphere, or as is noted in construction lingo, vent to daylight.
  2. Keeping the door open to  other interior spaces is a method of allowing the moist air to distribute into the interior environment of the home.  Although not conducive to privacy and certainly not as effective as an exhaust fan, keeping the door open will help. As the saying goes with any type of negative environmental issues, the solution to pollution is dilution.  Moist air being introduced into a larger space will have less of a negative moisture accumulation effect than in the confines of the bathroom.
  3. Keeping the bathroom window open is another method of ridding the interior bathroom air of moisture.  This technique could cause heating and cooling issues within the home, dependent upon the season, but is a means of allowing the moist air to move from the bathroom environment.
  4. The use of an electric dehumidifier within the bathroom is another means of reducing the moisture within the air.  Unfortunately an electric dehumidifier uses electricity and is somewhat noisy when in operation. The introduction of a timer, that would allow the functioning of the dehumidifier during the day, in lieu of the night time, could be a solution to any noise issue influencing sleep within the household.
  5. Placing of dehumidification, absorption products within the bathroom environment will reduce the amount of moisture in the atmosphere.  There are several different materials that are manufactured to allow the reduction of atmospheric humidity. These products have a life expectancy and must be replaced on a scheduled basis.
  6. Keeping the bathroom heated with a space heater will allow the moisture generated by the water vapor in the bathroom to remain suspended in the warmer air.  Warm air will hold more water than cooler air. Therefore the overall humidity of the bathroom will be higher with warmer air. Unfortunately the warmer the air, the more condensation will develop and occur once the air cools off.
  7. The elimination of exposed sheetrock within bathrooms is recommended to reduce the possibility of mold growth.  Mold needs a food source, and in many instances the cellulose within the top layer of the sheetrock will provide this food source.  This is the reason that most older bathrooms were tiled on the floors and the walls. Mold will not grow on a tile surface, it may occur in the grout lines of the tile or other sealant areas, but you will not find mold growing on the surface of a hard, non porous surfaces, such as tile.
  8. The simple act of undercutting the bathroom door more than usual, will allow the movement of bathroom moisture laden air to flow under the door and out into the other interior spaces of the home.  In this manner, the door can be left closed, but there will be air movement under the door.

      9.) The installation of a door louver in the bathroom door will also increase the flow of air from the interior of the bathroom to the other portions of the home.  Like undercutting the door, the addition of a louver allows the door to be shut for privacy, but also increases the air flow and reduces the accumulation of the moist air within the bathroom.

If there is any room in a residential home that should be vented, it is the bathrooms.  The accumulation of interior excessive moisture is not a good thing and should be addressed.  The best situation is to have a good ventilation fan that vents the bathroom allowing the moisture laden air to exit the bathroom environment.  However, if a vent fan is either not installed, or is impractical, any of the other suggestions within this article will reduce the accumulation of moisture as well as the possibility of mold growth.

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