Humidity, Flooring and Mold
Colder temperatures usually mean drier air – inside and outside. That’s why hardwood flooring manufacturers issue written guidelines that the owner must keep indoor relative humidity levels between 39 and 60 percent.
When humidity drops too low, the floor with shrink. Too high, it will expand and cup.
But most people have no idea what their indoor humidity levels are at any given moment. And there are more reasons to know than just for maintaining your flooring’s health. It is important for your own health, too.
High relative humidity -- and I would say 60 percent is too high even if all your floors are hardwood -- can promote mold growth. The majority of industrial hygienists will tell you that indoor relatively humidity should not exceed 55 percent, and that keeping humidity under 50 percent is preferred.
How do you do this? Start with a simple hygrometer, like the one pictured with this post, available at most home supply stores for about $10. Mine has been tested against several more expensive meters, and found to be amazingly accurate. Note, however, that the only accurate reading will be with a meter that has been calibrated.
To keep humidity levels up during the winter, a humidifier that is attached to your HVAC system will most likely be needed. But you should also check your hygrometer daily to make sure humidity is not too high, and turn the humidifier down or off if it is. I try to keep relative humidity between 40 and 50 percent, though 40 can be a struggle to achieve in the dead of winter.
In the summer, a whole house air conditioner that is correctly sized for you home should be able to remove excess humidity that occurs in many regions of the country during the summer.
But you should also own a dehumidifier to use as a backup, and turn it on when humidity is out of control.