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June 30, 2014

How a CFM fan rating affects ventilation

CFM-bathroom-venting-wall-capMoisture is a constant enemy in a home.  Too much will create mold and other problems.  Too little will aggravate allergies and create static electric shocks.  Active venting is one important way you can help manage the water in the air.

The bathroom can often be a home’s greatest source of moisture issues.  Every day people run water through toilets, showers and bath faucets, all inside some of their home’s smallest rooms.  Each time they do, they’re increasing the humidity in that environment.  If there’s no way to get the water vapour out, they’re setting the stage for problems.

The moisture created when a person takes a bath or shower will encourage mold to grow.  That mold can cause all kinds of health issues including coughing, nasal stuffiness and other respiratory illnesses.  Damp indoor environments can also ruin walls, cracking paint and causing wallpaper to peel.  Metal components in the bathroom may start rusting and the water can even enter surrounding duct work, joists and framing.  Considering all those potential concerns, it only makes sense to include a ventilation fan in a well-designed bathroom.

More than just removing water vapour, a fan will also help get rid of unpleasant odors that can occur in a lavatory.  A properly installed fan will pull stale air out of the bathroom and force it outdoors through a wall, soffit or roof vent.

A good outside bathroom vent should be located away from passive soffit vents, which could allow moisture to re-enter the home and gather in the rafters.  It should incorporate a one piece design, and form a watertight seal with the roof or wall material around it.

Fans are typically rated according to their CFM, or their ability to move air.  The more cubic feet it moves per minute, the larger the space it can ventilate.  A general guide for developers, contractors and builders is one cubic foot per minute for every square foot of floor space in a bathroom, assuming an eight foot ceiling.  An appropriately sized fan will effectively limit the water vapour that collects on bathroom surfaces.

It may never become someone’s room of choice to spend time in, but the fact remains the bathroom is a space we all rely upon every day.  Keeping it safe and pleasant is vital to an enjoyable home.  The small cost of ventilation fans will help to keep bathrooms in peak condition, while avoiding expensive mold remediation bills down the road.

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