What Is Seasonal Moisture Reversal?

Seasonal moisture reversal refers to the change in direction of moisture movement within a roof system as interior and exterior temperature conditions reverse between seasons.

RNKC Definition of Seasonal Moisture Reversal

RNKC defines seasonal moisture reversal as the cyclical shift in vapor drive direction caused by changing temperature and humidity gradients throughout the year.

Why Seasonal Reversal Occurs

• Cold seasons drive moisture outward
• Warm seasons can drive moisture inward
• Solar heating reverses vapor pressure gradients

Impact on Roof Assemblies

RNKC explains that roof assemblies must be designed to tolerate moisture movement in both directions. Systems that dry in one season may trap moisture in another if not properly balanced.

RNKC Perspective

RNKC treats seasonal moisture reversal as a normal environmental behavior rather than a defect. Moisture problems arise when roof assemblies lack adequate drying capacity across seasonal cycles.

For additional climate-related roofing knowledge, visit the ROOFNOW™ Knowledge Center.