Fan Theory

Another home building blog, The Impatient Home Builder, recently published a great post on a topic I happen to care a lot about.

House fans are an important part of a healthy home. Growing up, I was told not to use our bath fan because it was too noisy, but I would open the window when showering so it didn’t cause moisture problems (really, I just didn’t want the mirror to be foggy). As an apartment manager later in life, I realized the damage caused by ineffective moisture removal. Close attention to home designs and problems over the past decade has led me to several strong opinions about house fans.

Consider Your Comfort

Master, attached, and shared bathrooms nestled near bedrooms should ideally have quiet fans on timers. The primary consideration is usability and comfort. A noisy fan that might stir light sleepers trumps most other concerns. A timer will keep you from running a fan at all hours. Ensure that you have high enough throughput for the size of the space you are ventilation.

Consider the Comfort of Your Guests

Any bathroom or powder room that adjoins a public space should be designed with consideration for guests during a social situation. A person should feel comfortable to have a coughing fit or use the loo without their sounds being telegraphed straight through the walls and doors.

Ensuring that you have a solid door with a minimal gap at the bottom is a good first step. Beyond that, a guest bath should have a slightly louder or more powerful fan. Something that moves over 100CFM with between 2.5 and 6 sones is good.

Don’t Trust Renters or Kids

People without a vested interest or understanding of the damage high moisture conditions can cause may not be inclined to turn on the fan every single time. The solution to this problem is simple and two-fold:

First, have the fan wired so it comes on with the light. Second, spend the extra money on a very quiet fan. Preferably 1.5 sones or less.

I’ve seen more than one case where rental units had a fan hardwired to the light but the renter took off the grille and unplugged the fan so it didn’t run at all. This is almost always due to an overly loud fan. Getting a quieter fixture in there will solve this problem almost every time.  Spending an extra $50 on the quiet bath fan can save you a lot more than that over time. Remember that water damage is insidious and you may not find out about the worst of it until well after the offending tenant is gone.

Your Biggest Fan

Most jurisdictions require a whole-house fan to be installed for new construction. If you aren’t required to have one, you should still consider having one installed. It is a more powerful fan that is set on a 24-hour timer which ensures your energy efficient home doesn’t suffer reduced indoor air quality, preventing buildup of high levels of CO2, CO, methane, etc.

Cooking Concerns

We bought a monster of a range hood. The Broan QP436 can move a whopping 630CFM. Fans over 300 CFM should be installed with a damper that allows a suitable amount of make-up air to flow into the house. A modern house is typically inefficient enough that it can draw in 100CFM when needed, but your range hood will be making a lot of noise with little to show for it if your house won’t admit as much air as the fan can push out.

In Conclusion

Spend some time thinking about how you will use your bathrooms and kitchen. Pick your ventilation fixtures carefully to maximize your enjoyment of the space and eliminate the risk of moisture damage.