Technical Tip 8: Improving Bathroom Ventilation and Reducing Mold

In many homes, bathroom ventilation isn’t a problem. A fan in the ceiling that’s vented out through the roof or side wall does the trick, along with the old-school tactic of simply opening a window.

But, if your customers are complaining about a musty smell, visible mold, peeling paint, or fogged-up mirrors, you know you’re dealing with a moisture issue. Foggy mirrors are one thing. But mold, or a musty smell with no visible mold? That’s a bigger problem. 

In this Tech Tip, we’ll look at some ways to improve ventilation and reduce mold in a bathroom.

Check out the fan. It could be a simple matter of not having the right-size fan. The bigger the bathroom (or the higher the ceiling), the bigger the fan needs to be. Customers need to consider the size of the bathroom, the amount of moisture that’s typically produced (many people taking showers each day? Or is it a guest bath that’s rarely used?) and the type of ventilation there is. A small bathroom, less than 100 square feet, will need a fan that has a capacity of 50cfm. For larger bathrooms, choose a capacity of 100 cfms or more.

Check the ductwork. Is it flexible? If so, it’s not the right ductwork for the job. It can trap airborne contaminants, which can actually make the problem worse. Code requires bathroom ventilation to be made of PVC or metal.

Use a recirculating fan. No exhaust venting? A recirculating fan passes the air through a filter and recirculates it. These are great options for interior half baths.

Notice the height of the shower door or curtain. If it runs all the way up to the ceiling, it will trap moisture that your fan, even if it’s properly sized, can’t suck out.

Those are bigger jobs for you, an HVAC pro. But your customers can do a lot to mitigate mold. Here are a few suggestions:

Clean the fan on a regular basis. People need to clean their AC’s filters and change their car’s oil filter, but they rarely think about cleaning their bathroom fans. It’s a simple matter of turning off the power to the fan at the circuit breaker, removing the fan’s cover and vac out any debris, wipe down the blades and replace the cover.  

Leave your shower door or curtain open. And your bathroom door too, for good measure. It helps circulate the air and dry it out faster. For curtains, make sure they are flat once they’re dry to prevent mold from forming there.

Clean the shower after every shower. Use a spray designed to be used daily. And deep clean the shower weekly.

Mop up any standing water. Sometimes, water seeps out of the shower and puddles onto the bathroom floor. Dry it right away to prevent that moisture from hanging in the air. Pro tip: use a mop and that water to do a mini-clean of the bathroom floor.

Install a skylight. This is a bigger project, of course, but for bathrooms without windows that are on the upper floor, a skylight is a great way to increase airflow and reduce moisture and mold, not to mention letting the sun shine in.

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