Best Bathroom Ventilation - Vent Away Moisture and Mold With These Tips

The American bathroom is undergoing a major renovation. The standard 5'x8' bathroom with a tub and shower combo is giving way to a spa-like setting with artistic styling and unique materials. Bathroom ventilation however, is frequently underpowered to handle the steam, humidity and warm temperatures that result, and won't prevent the bathroom mold and mildew that can follow.

There are many new options for bathroom renovations that will help you create a bathroom that looks great, performs well, and is relaxingly beautiful. Included among these, are some real advances in bath ventilation that can keep these rooms looking great for years to come.

How to vent your steam
Warm temperatures and lots of humidity make a bathroom a hot spot for mold and mildew growth. Uncontrolled humidity can cause allergy problems and damage windows, walls and ceilings by encouraging the growth of molds, mildew, bacteria, dust mites, dry rot and insects. To prevent your bathroom from becoming a Petri dish, you'll need a powerful bathroom vent fan.

There are three kinds of fans that can do the job; bath fans, remote fans and energy or heat recovery ventilators. Bath fans are installed directly in the bathroom, usually on the ceiling, and discharge moisture to the exterior via a duct. Remote fans, also known as multi port ventilators, are mounted elsewhere in the building, such as in the attic, and use ducts to exhaust air from one or more bathrooms at the same time.

In addition to being able to handle larger baths, one popular advantage of multi port ventilator is that they are extremely quiet. Since the fan is mounted in a remote location, very little sound is transmitted to the bathroom.

Today's newer homes may, but don't always, include bathroom ventilators. Surprisingly, in some areas of the country, builders are not required to install a bath fan if the bathroom has a window, as if you could just leave a window open on a chilly winter morning! If your builder expects you to shower in sub-zero conditions, make sure you ask for a bath fan to be installed when the bathroom is built.

In addition, it is very important that bath fans be vented correctly. One of the most common mistakes builders make is venting the bathroom into the attic, which just transfers the moisture and mold problem overhead. Efficient bathroom ventilators must vent to the outdoors, sending moisture back into the environment.

Typically, the exhaust vents should be located over or near the shower or bathtub and in an enclosed water closet. With windows closed, exhausted air will be replaced by makeup air from adjacent rooms or forced air system registers. Bathroom doors should also be undercut by at least 1 inch to allow return air to enter the room.

Your bathroom ventilator should be left on for 20 minutes after use of the bathroom. A timer is a good solution, allowing the fan to turn off automatically at the proper time. For steam showers it is best to have a separate fan in the steam room that can be turned on after use.

For bathrooms up to 100 square feet in area, the Home Ventilation Institute (HVI) recommends that an exhaust fan provide 1 CFM per square foot (approximately eight air changes per hour) to properly ventilate the bathroom. For example, if the bathroom is 8' x 5' (with 8' ceilings), your bathroom area is 40 square feet. At 1 CFM per square foot, the minimum recommendation is a fan rated at 40 CFM.

For bathrooms above 100 square feet in area, HVI recommends a ventilation rate based on the number and type of fixtures present, according to the following table:

• Toilet: 50 CFM


• Shower: 50 CFM


• Bath Tub: 50 CFM


• Jetted Tub: 100 CFM

For example, if the bathroom is 20' x 12' with a tub (without jets), a shower enclosure and an enclosed toilet, each fixture will require 50 CFM, so the minimum recommendation for a ventilator is 150 CPM.

For bathrooms this size, you have two options:

1. Install a 50 CFM bath vent fan over the tub, one in the shower and one in the water closet. This method is very effective and will provide ventilation where and when it's needed.


2. Or, install one 150 CFM fan. The air will then be pulled through the entire room and exhausted at a central location.