Duct Fan

A healthy house requires enough ventilation in the kitchen and bathrooms. Most homes these days do not have provisions for natural ventilation, which is where air duct fans become very handy. Without a vent fan, moisture can build up in the room, leading to mold growth, door hardware rust, and paint damage.

About the Capacity of Duct Fans

An air exhaust fan is recommended to have a capacity of 10-15 times the air volume in the room (height x width x length). If a fan is being ducted out, it is usually better to increase the capacity to offset air resistance caused by the duct, grilles, bends, etc. To work out the required capacity, a good starting point is calculating the height x width x length of the room, then multiplying the total by 15 for a bathroom and 10 for a toilet.

What are the different types of duct fans?

Typically, there are three types of exhaust fans: axial duct fans, centrifugal duct fans, and inline duct fans. An axial vent fan pulls the extracted air through an impeller, and then out through the hole in the external wall. They are the most common extractor fan and are ideal for bathrooms and smaller rooms where ducting of 2-3 meters is required. Centrifugal vent fans extract air at right angles to the fan intake and then spin the air outwards to the outlet by centrifugal force. They can duct more air and are ideal for rooms with longer ducts. Inline vent fans often sit in ceilings above the room, make a lot less noise, and can be used in situations where extremely long ducting is required. They are ideal for rooms without an external wall, or where the noise of the extractor fan is an issue. Since there isn't a need for a hole in an external wall, they can also be used to prevent heat loss.