10/17/2022
Relative humidity in the attic on a rainy day....
In term of relative humidity and our attics, when our fans are not running, we still have effective ventilation. The openings that are created for the fans operate as natural ventilation when the fans are not in operation. By this chart, relative humidity increased in the attic close to 70% with effective natural ventilation, then the fans activated and immediately dropped the humidity into the 40s. This is the primary reason that ventilation is imperative in the winter months, due to moisture. Active ventilation in our opinion will beat passive ventilation any day. This chart proves that. The goal of winter ventilation is to keep your attic dry, which reduces the amount of moisture your insulation will absorb. The better the ventilation, the better your insulation performs.
