Does Your Bathroom Fan Suck up Toilet Paper? It Should.

Have you noticed that your bathroom fan isn’t quite sucking out the humidity quite like it used to?

It might be time for an upgrade. A classic, simple DIY trick is to hold up a piece of toilet paper to the whirring fan. If the TP won’t stay in place, the fan isn’t pulling its weight (or pulling out much of anything).

If your bathroom doesn’t have a fan, it’s a good idea to put “bathroom ventilation” near the top of your home reno to-do list. Not only can the moisture left over from baths or showers make mildew or mould grow in your corners, causing paint and/or wallpaper to peel off  — but  over time, the accumulated moisture can also inflict water damage on your drywall and even make its way into your structural beams and joists, affecting the structure of your home.

Choosing the Right Ventilation System

Measuring Space

Ventilation is measured in the cubic feet per minute (CFM) at which air is moved through a vent system. According to the US-based Home Ventilation Institute (HVI), an exhaust fan should provide one CFM per square foot for a small bathroom. So for example, a bathroom measuring 50 square feet should have a rate of 50 CFM. For larger bathrooms (100 square feet and up), CFM rates are measured according to the number and kind of electrical fixtures in the room — see the HVI bathroom ventilation page for details. CFM rates are indicated in a product’s technical specifications.

Understanding Duct Pressure

Static pressure: this is the resistance that the air will encounter when flowing out. If the air ducts are too small in diameter, have too many “elbows” or are simply sloppily installed, the CFM will be counteracted by higher static pressure. Check that your fan’s CFM is calculated at 0.25 i.w.c. (inches of water column), and ensure that the duct path is as simple and straight as possible.


Sones is a measurement of loudness. You probably don’t want an annoyingly loud fan. The lower the sone rating, the quieter the fan.

Energy efficiency

Fans use energy, and the more powerful they are, the more they’ll add to your hydro bill. Make sure to look for an Energy Star model.

For added comfort, look for products that are certified by the Home Ventilating Institute (HVI), an institute that qualifies products on a rating system.

Once your fan is installed, remember to run it for a good amount of time after your bath or shower. (HVI recommends 20 minutes, though other experts say 5-10 is fine).

More tips for bathroom ventilation

  • If you prefer to keep your door closed while the fan is on, make sure the door is undercut so that fresh air is flowing in to replace the moist air going out!
  • You can also install a fan with a timer, if you choose, in order that the fan cuts out on its own after 10 or 20 minutes.

Water and humidity can be your home’s greatest enemy. Make sure you take the time to make sure your home is well ventilated. You won’t regret it!

Not sure if your home has already grown mould from excessive humidity? Do an air quality test to find out. Call to book: 514-426-1095