Bathroom Ventilation

Home Inspection Shower


When I was younger, I thought I knew exactly what a bathroom fan was for. When you grew up in a house sharing a bathroom, it was only kind after a ‘reading’ session in the bathroom to turn on the fan on the way out. Family harmony was at stake.


While bathroom fans are very useful at helping keep odours down, they play an even more important role in protecting your house from high levels of damaging humidity. 


How Does High Humidity Damage our Homes?

In Canada, our homes are largely built out of organic materials like wood studs, paper-backed drywall, cellulose insulation, wooden joists, and plywood sheeting. In our wet West Coast, there are also billions of spores for moulds, mildews, fungi, in the air not to mention all the wood eating insects. When our warm homes are too wet, we create a perfect breeding ground for these organic organisms to start literally eating our homes. The role of a fan is to help pull that warm moist air out of the house from showers and baths before it has a chance to absorb into the house's structure.


Why was my Bathroom Built with No Fan?

Code requirements have not always required a bathroom fan. Up until the 80’s, it was considered acceptable by Building Authorities to have a window that opened as ventilation for a bathroom. Thanks to some high school physics that say cool air can hold less moisture than warm air, even on a cold rainy winter day, keeping a window open in the bathroom can bring in cool dry air in and replace the warm moist air. The problem of course is that nobody wants to stand in a hot shower in the morning with a window wide open when it is near freezing outside. If you want to avoid a cold air morning shower, adding a bathroom fan is a great alternative.


Do I really need to run the Bathroom Fan? It is noisy.

Yes, you really need to run that bathroom fan. As Home Inspectors, we all too often are in houses where high moisture levels from bathrooms and cooking have not been well ventilated and there are signs of water damage around windows (where water likes to condense like a cold glass of water on a hot day), on ceilings and walls, and along the bottom of the roof in the attic. In the worst case scenarios, it will cost thousands of dollars to open up walls and ceilings and replace mould damaged materials. We also see in home inspections bathroom fans vented into the attic space. This is worse than no fan at all as we are pumping large amounts of water into an attic where we won’t see the eventual damage and where there are cold surfaces for the water to condensate on.


My Bathroom Fan is so Noisy I Can’t Stand it.

There are many different fans available and some are nearly whisper quiet. If your fan is too loud for your comfort, it may need some maintenance or the whole fan may need replacement. Installing a fan needs a little electrical done which requires an electrician but the installation itself can be done by a good handyman.


So next time you are about to step into your shower, give a little consideration to the health of your home and turn on the fan. Let it continue to run for about 30-60 minutes after the shower for best performance. This is easily accomplished if you install a delay timer.


By James Bell - Owner/Operator of Solid State Inspections Inc.