Moisture Management Flashcards

What is the primary function of a Class II vapor retarder?

Answer: Slow vapor diffusion without eliminating it

A Class II vapor retarder (permeance 0.1–1.0 perm) slows but does not stop vapor diffusion, allowing some drying potential.

In a cold climate, where should the vapor retarder be located in a wall assembly?

Answer: On the warm-in-winter (interior) side of the insulation

In cold climates, the vapor retarder belongs on the interior (warm) side to prevent interior moisture from diffusing into the cold wall cavity.

Which diagnostic tool is most appropriate for detecting moisture trapped inside wall cavities without invasive sampling?

Answer: Infrared thermography camera

Infrared thermography detects temperature differentials caused by evaporative cooling from wet materials, revealing hidden moisture.

What does a dew point calculation help determine in building science?

Answer: The surface temperature at which condensation will occur

Dew point calculation identifies the temperature at which air becomes saturated and condensation begins on a surface.

Which of the following building materials has the HIGHEST vapor permeance?

Answer: Unpainted gypsum board

Unpainted gypsum board is highly permeable (50+ perms), freely passing water vapor, unlike poly, kraft facing, or XPS.

A homeowner notices frost forming on the attic roof deck in winter. What is the MOST likely cause?

Answer: Excessive air leakage from conditioned space into the attic

Warm, moist interior air leaking into a cold attic deposits moisture on the cold roof deck, forming frost when temperatures drop below freezing.

What is the recommended minimum slope for a finished grade adjacent to a foundation to prevent bulk water intrusion?

Answer: 5% over 10 feet

BPI and building codes recommend at least a 5% slope (6 inches drop over 10 feet) away from the foundation to drain surface water.