Bathroom and Kitchen Fans: Venting Into the Attic

Moisture in the home can be the source of many problems and addressing this issue is critical in preserving the functionality of a structure. Since bathrooms and kitchens are two of the largest sources of moisture production in the home, it is imperative to properly ventilate these areas. The most common and effective way to do this involves the installation of a fan on the ceilings of bathrooms and over the cooking areas of kitchens and exhausting the moisture and odors through the roof. This helps to quickly move water vapor from the interior to the exterior of the home.

Bathroom vent improperly terminated.

While these fans are excellent in preventing the build-up of moisture, it is important to ensure that the moisture is properly exhausted outside of the home. A common defect found in many homes is a fan that exhausts into the attic space. This can cause a significant problem because it allows moisture to accumulate and encourage mold growth. This condition also promotes the presence of other wood destroying organisms, most of which prefer elevated levels of moisture. While it was once acceptable to vent bathroom fans into the attic space near a roof vent, this creates conditions that leave the attic susceptible to mold and other issues.

Bathroom vent exhausting into attic space.

To be properly terminated, bathroom fans should exit the home through stem vents that are specifically used for this purpose. These stem vents should be properly connected to the bathroom ducts to ensure that moisture is traveling to the exterior, not the attic space. Likewise, kitchen fans should vent through vents in the roof, moving moisture and odors from the interior to the exterior.

Bathroom vent exhausting in attic space. Mold conditions galore!

Since mold colonies become active when the moisture content in wood reaches around 20%, exhausting water vapor outside of the home is a simple way to help improve ventilation in your home and minimize the amount of water in the structure. While an operable window is also an acceptable form of ventilation for bathrooms, many people do not open windows in the winter, allowing moisture to accumulate in these areas. In conclusion, if fans properly terminate through stem vents that exhaust to the exterior, they are are excellent at transporting both moisture and odors away from the home.