07/12/2025
Attic Air Flow & Proper Ventilation
Recently I was installing an exhaust fan in a shower that has been absent of an exhaust fan since the home was built, a very common occurrence in many homes even new constuction, many master bathrooms include a separate toilet room, sometimes referred to as a water closet, enclosed within the larger bathroom. While these spaces often have their own exhaust fan, that fan is typically too small or too far from the shower to effectively remove humidity from the overall bathroom environment.
Trapping moisture created by a hot shower is a recipe for inhibiting mold growth, which can lead to all kinds of health complications, such as Asthma, Brochitis & Chronic Sinus Infection.
On top that, many exhaust fans expel heated or moist air directly into the attic
Improper Venting=The Hidden Moisture Trap
In many older homes—especially those built before 2005—it’s common to find bathroom exhaust fans venting directly into the attic. While this may seem harmless, it’s actually a recipe for long-term moisture damage, even in bathrooms that don’t have a shower.
Take for example a toilet room (also known as a water closet). These spaces are usually enclosed within a larger bathroom and are often equipped with a small, dedicated exhaust fan. You’d expect them to stay dry—but if that fan vents into the attic through a short, uninsulated duct, moisture can still become a problem.
I used a fan that facilitated a 6” duct, and ran a 6” insulated duct out through the soffit with a soffit vent kit with a damper,
When I was installing the soffit vent kit I removed a soffit vent to view
access and noticed, the hole cut for the soffit vent was about a 1/3rd of the size of the vent, immensely impeding air flow, and all the louvered vents were facing the wrong way!
I purchased new vents and painted to match the current soffit, cut the soffit vent holes much larger and instslled the louvered vents facing the correct way,
Having proper attic air allows allows heat to escape in the summer, reducing the strain on your AC, in the winter, having proper air flow will allow the insulation to stay dryer and working more effectively.
Action plan:
1) have proper exhaust fans where needed
2) Check to see if your exhaust fans vent to the
outside
3) Check to see if soffit vents are adequate in terms
of airflow and instslled properly
Air flow is key!