How to Vent a Bathroom with No outside Access

Do you have a bathroom with no access to outdoor space? Noticed mold growth or any structural issues inside your internal bathroom with no outside access? Well- you’re not alone. Most homeowners usually find it difficult to properly ventilate their bathrooms that lack outside access. Read on to find out how you can properly vent such a bathroom- and the associated costs.

Do bathroom exhaust fans need to be vented outside?

Yes, bathroom exhaust fans should be vented outside- either through a duct connected to a sidewall vent or through the attic. In the latter case, you should vent the fan through the roof and not directly into the open attic, as this will cause moisture issues on the lower side of the roof.

How to Vent a Bathroom with No outside Access

Install a Wall Vent Fan

To vent a bathroom with no access to outdoor space, you need a bathroom fan venting system. When selecting the appropriate fan for your bathroom, take into account the fan size. This is a measure of how much air the fan can move at any instance. Fan size is usually gauged in Cubic Feet per Minute (CFM).

Therefore- to properly ventilate a standard-sized US bathroom, you’ll need a 40CFM bath fan. However, if the shower/bathroom undergoes frequent use, then you should consider getting a bath fan with a larger capacity.

Installing a Floor Duct

If you live in a house with no outside access- such as inside an apartment complex- you can also ventilate the bathroom through the floor. This type of vent is also recommended if a ceiling vent is not a good option. Installing a floor duct is difficult to undertake as a DIY project- and according to several building codes- can only be undertaken by a licensed HVAC contractor. The HVAC expert will professionally install a grated floor duct that releases moisture into outer space via the external wall.

Install a ceiling vent

A ceiling fan is a great way to ventilate a bathroom with no outside access via the roof. Some modern ceiling vent brands also double-up as bathroom lighting fixtures- thus offering great value for money.

Place a dehumidifier in the bathroom

A dehumidifier helps to ventilate rooms by extracting excess moisture from the air. You can simply install it in a corner of the bathroom and turn it on. However, due to the excessive amount of moisture in bathroom air, you’ll want to empty your dehumidifier’s reservoir at least every 24 hours if you choose to use it in the bathroom.

How Much Does it Cost?

The cost of venting a bathroom with no outside access largely depends on the type of vent. Generally- though- a bathroom ventilation project will cost you anywhere from $230-$550.

Signs of no ventilation in bathroom

Mold Infestation

If you notice mold growth on your bathroom walls and ceiling, it means that the bathroom is poorly ventilated and steam/moisture build-up in the air is making the room more humid. High humidity conditions provide a suitable growth habitat for mold and mildew fungi.  

In addition, if you notice that you’re always sneezing or your skin itches every time you enter the bathroom, it means you have a mold problem due to poor air circulation. Mold spores can trigger respiratory and dermatological health issues when inhaled. These include sneezing, coughing, wheezing, throat irritation, skin irritation, and eye irritation.

A Stuffy Odor

If your bathroom has an unpleasant, stuffy smell, it means that the air in the bathroom is laden with retained moisture.

Rusty Pipes

If you notice metal pipes in your bathroom getting rusty despite not frequently coming into direct contact with water, it’s most likely due to poor ventilation, as trapped steam in the air corrodes the metal pipes.

Wall Problems

Poor bathroom ventilation can also cause various wall issues such as staining- or the paint finish peeling off. Therefore- if you notice black marks on your concrete bathroom walls or ceiling; or the paint coming off of the walls, it’s time to call in a HVAC expert.

Can you use ductless bathroom exhaust fans instead?

If you don’t fancy installing exhaust ducts in your bathroom, you can opt for ductless bathroom exhaust fans, which dehumidify and deodorize bathroom air using a charcoal-based filter system. Also known as a recirculating fan- this type of bath fan doesn’t disperse air outside the house. You can easily mount a ductless bath fan to the wall and ceiling.

Due to its lower blade speed, this type of fan sucks in large amounts of air into its filter with every rotation. This ensures that the whole bathroom is dehumidified and deodorized within the shortest possible time. Below are some of the pros and cons of a bathroom extractor fan that lacks ducting:

Pros of Ductless Bath Exhaust Fans

Easy to Install

Unlike duct fans where you have to install the fan as well as the duct pipes leading to the building’s exterior, installing a ductless bath fan doesn’t take much. You simply need to mount it to the wall or ceiling.

Energy Efficient

Considering the length of the duct pipes used and the change of directions involved at the elbows, it takes more energy for a ducted fan system to blow air through the ducts. By comparison, ductless bath fans only require a little amount of energy for the filtering process.

Cons of Ductless Bath Exhaust Fans

Building Code Restrictions

Depending on where you live, the building codes in that state may restrict the installation of ductless bathroom exhaust fans in buildings with certain types of structural designs. Some building codes also stipulate that the installation of this type of bath fan should only be undertaken by a certified HVAC professional.

High Maintenance Requirements

Their functionality notwithstanding, ductless bath fans are quite difficult to maintain. To keep them functioning optimally, you’ll need to occasionally replace the charcoal filter. It also calls for regular cleaning and servicing of the motor and air vents. Other parts that you should also consider servicing include the speed controls and the rocker control switches.

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