The main purpose of the bath fan is to remove steam and moisture from the air. So the fan should be located over the primary source of moisure in the room – your shower.
The fan should be placed between the shower and toilet to ensure efficient circulation of air and ventilation of moisture.
Follow the Moisture
First, the fan should be located in the area of the bathroom that is exposed to the most moisture. This is usually the area over the bathtub or shower. You can place the fan directly over the bathtub or shower base, but it's sufficient to position it anywhere near the bathing area.
Normally exhaust fans are place up high where the hot air in the room is to get is out and the door usually will have some form of grille on it to allow new air to enter the room and create circulation.
The air travels through ductwork that is connected directly to the ceiling vent. Another duct runs from the housing to the exterior of the home, again being, the roof, or overhanging soffit. The blower motor then propels the air from the housing unit through the ductwork connected to the exterior of the home.
That's why it's fine to have bathroom vents in a basement or lower floors to leave through the side of the home. To help your attic stay clear of mold or mildew, make sure all exhaust fans running through the attic leave through the roof. For one, you'll lessen the chance of the warm air getting back into the attic.
2. Keep Vents and Ductwork Clean. Even the best exhaust fan won't perform well if the vents and ductwork are clogged with dust and debris. Regular cleaning ensures optimal airflow and prevents blockages that can reduce the efficiency of your ventilation system.
Extractor fans work best when they are fitted as near as possible to the source of moisture in the air. For many people, this will be over their shower enclosure or bath. However, as bathroom fans are an electrical item, it is vital that you ensure you have the correct IP rating for this bathroom zone.
Using bathroom fans to vent the hot air that gathers near the ceiling can help keep things cooler. For those with a second story, this can really help keep the upper floor cooler. I turn on my bathroom fans upstairs in the early evening hours. This helps vent the built-up heat of the day.
Exhaust ducts should always terminate outdoors (refer to applicable codes for vent termination clearance requirements). Running exhaust ductwork up to a vented attic or just in front of an attic vent (gable, ridge, or soffit) is not sufficient. The exhaust should be fully ducted to a point exterior to the home.
Flexible duct is acceptable for a bathroom exhaust fan. Approved by building codes-Chapter 15 of the International Residential Code (IRC), it is available in PVC, PVC coated aluminum, aluminum and insulated aluminum.
Where is the best location to install my bathroom exhaust fan? Typically a bathroom exhaust fan should be mounted as close to or inside (if rated for tub shower use) to the shower or tub as possible. This will maximize the effectiveness of the unit. Units located in a powder room, should be directly over the toilet.
One Foot In, One Foot Out – Ideally, you should place a bathroom fan in the ceiling about 1 foot from the shower and between the shower and the door.
To fulfill the local exhaust airflow requirements of ASHRAE 62.2 (2010) and the International Residential Code (IRC 2021, Section M1507), bathroom fans should have a mechanical exhaust capacity of ≥ 50 cfm for intermittent operation or ≥ 20 cfm of ventilation when operated continuously.
You should place outward-facing fans on the warmer side of your home to blow the hot air out and inward-facing fans on the cooler side to draw cool air in, says Barry Jacobs, vice president of product development at Comfort Zone, a home environment product company.
Zone 1: The exterior of the bath or shower tray to a height of 2.25 metres above the finished floor level. Zone 2: Extends to 0.60 metres beyond Zone 1 to a height of 2.25 metres above the finished floor level.
For bathrooms, the best area is near the shower or the bathtub. For kitchens, the fan should be installed near the ceiling because this is where the hot air gathers.
When the fan is in the center of the bathroom, it actually drags the moisture from the shower across the room rather than venting it straight out and away. To prevent this, bathroom fans should be placed in the shower or just outside of the shower to eliminate moisture at the source.
A fan that is too big can cause a bathroom to be cold and noisy. This is why calculating the correct CFM is important.
If you have the fan on, and your door is closed, your bathroom fan will have to fight to pull fresh air through the tiny cracks. As a result, your fan will be less effective. Your bathroom should at least have a 12mm gap between the finished bathroom floor and the door.
Adhering to the following basic rules will ensure condensation is efficiently dealt with: Always install the fan at the source of the humidity in the furthest window, wall or ceiling from the door and at a high level.
Bathroom exhaust fans are typically used during bathroom usage; however, sometimes they are left on for extended periods to clear humidity and/or fumes out of a space, often left unattended during these periods, this is when they can turn into an electrical fire hazard.
The main purpose of the bath fan is to remove steam and moisture from the air. So the fan should be located over the primary source of moisure in the room – your shower.