How To Reduce Moisture With HVAC System

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Lenny Steinberg asks,

I have a 3-story house with a basement. The home has 3 zones of HVAC. Lately I've noticed a musty smell in the stairways which do not have vents and are not air conditioned. The the hallways on the sleeping floors have the same musty smell. I assume this comes from moisture. How can I adjust my HVAC to get rid of the odor?

Our Answer

It sounds like you're not getting sufficient airflow in those spaces. Look at the position of your return vents. If they're in closed-off rooms, not hallways, be sure to undercut doors so that there's at least one inch of space between the bottom of the door and the floor. This way when doors are closed, air can be returned and recycled. If you're not getting good return air back, you could be developing some moisture. Good luck!