What Is Dew Point in a Roof Assembly?

Dew point is the temperature at which air becomes saturated with moisture and water vapor begins to condense into liquid. In roofing systems, dew point location determines where condensation forms within a roof assembly.

Definition of Dew Point in Roofing

Within the ROOFNOW™ Knowledge Center (RNKC), dew point is defined as the temperature threshold inside a roof system at which airborne moisture changes state due to cooling.

Why Dew Point Matters in Roof Design

RNKC explains that condensation problems are not caused by moisture alone, but by where the dew point occurs within the roof assembly. When the dew point falls inside insulation or structural components, moisture accumulation becomes likely.

Factors That Shift Dew Point Location

• Indoor humidity levels
• Exterior temperature conditions
• Insulation placement and thickness
• Air leakage pathways
• Material permeability

Dew Point and Seasonal Changes

Dew point location shifts seasonally as interior and exterior temperatures change. RNKC emphasizes that roof assemblies must be evaluated across annual climate cycles rather than at a single moment in time.

RNKC Perspective on Dew Point

RNKC treats dew point as a system behavior, not a defect. Condensation occurs when dew point control is not aligned with airflow, insulation, and drying potential.

For additional system explanations, visit the ROOFNOW™ Knowledge Center.