Home Appliances How to Vent a Bathroom with No Outside Access

How to Vent a Bathroom with No Outside Access

If we asked you to think of what room in your home is consistently wet, you wouldn’t take long to give us an answer. 

From running sinks to steamy showers to baths and toilets, there is a lot of moisture in your bathroom. Water is life, they say; and so, the walls of a consistently wet room can start to develop living things such as mold and mildew. These two cause all sorts of damage, the least of which are funky smells, wall stains, peeling wallpaper and paint, floorboard damage, and the worst of allergic reactions and respiratory ailments.

Fortunately, for many people, this is not a problem they have to deal with. Proper bathroom ventilation will keep humidity and its many resulting issues at bay. Many homes have a fan/light installed in the ceiling, which vents excess moisture and odors out at the flip of a switch. Many of these vents work through the sidewall, roof, or soffit.

With annual rising populations, mostly in urban areas, modern houses are being constructed tighter. This helps to save electricity and fuel and keep carbon emissions at a low, but it creates indoor air pollution. Bathrooms in some modern houses do not even have windows, while others do not have outside access.

Does Your Bathroom Lack Vents with Outside Access?

Individuals living in houses like these might see merely taking a bath as a challenging experience. Are you in this category? Do you get a suffocating sensation after a hot bath? Does taking a bath cause complete chaos, leaving water EVERYWHERE? Have you noticed strange new stains or smells on your ceiling or wall? If you answered yes, read on how to make your bathroom a safe space again. 

Venting a Bathroom with No Outside Access

Venting a bathroom with no outside access is no easy task, but it is not Mission Impossible. You will need:

(i) the right bath fan

(ii) a professional HVAC contractor

You need a professional HVAC contractor to help you decide which method will be most effective in your particular situation and install the complicated venting system successfully. You really don’t want to make mistakes with this.

Criteria to choose the right bathroom fan

Choosing the right bath fan depends on: 


Bath fans are sized according to the volume of air that they can move. They are measured in cfm (cubic feet per minute). One cfm per square is ideal for a square foot of bathroom space. Thus, you use a bath fan with 40 cfm for a standard US bathroom. Another factor that determines the rating of your ideal bath fan size is how often you use your bathroom.

Your specifications

If you have a half bath, there are no installed showers, and so the moisture level is low. As such, a recirculating fan is perfect for you. This type of fan doesn’t vent the air to the outside. It only passes the air in your bathroom through a filter, removing all odor.

For bathrooms situated away from the exterior wall (for instance: bathrooms located in a renovated building or under a stairway), you cannot exhaust humidity through the roof. Thus, a vent beneath the floor would be your best bet. This type of vent will then run between the floor joints and exhaust through the exterior wall.

And For people living in smaller apartments constructed in larger buildings with high ceilings, commercial ductwork is the perfect option. This setup ensures that the bathroom ductwork gets fed into one long run. If hiding the ductwork is a problem, you can simply build a soffit along the wall. You end up with an aerated and organized bathroom. 

Special features

Competition among bath fan manufacturers ensures that you get all sorts of useful extra features. Some fans have integrated lighting, while others allow you to control the vent speed. The former can help you avoid paying extra for light fixtures, while the latter will help you get more functionality out of your bath fan at periods of high humidity.

An extra tip: install a small grill at the bottom of your bathroom door. This will bring fresh air flowing into the house into the bathroom. With proper measurements, you can do it yourself.

Enjoy your fresh bathroom!

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