CMI Moisture Intrusion & Building Science 2

Question 1

In building science, the 'dew point' is defined as the temperature at which:

Accepted Answer

Relative humidity reaches 100% and condensation begins on a surface

Answer

The dew point is the temperature at which air becomes fully saturated (100% relative humidity) and water vapor begins condensing into liquid on surfaces. Capillary action is a separate liquid-water transport mechanism; HVAC mode changes are operational settings unrelated to dew point; and mold germination requires sustained moisture but has no fixed dew-point trigger.

Question 2

Which type of vapor retarder is classified as 'Class I' per the International Residential Code (IRC)?

Accepted Answer

Polyethylene sheeting (6 mil)

Answer

Class I vapor retarders have a permeance of 0.1 perm or less; polyethylene sheeting (6 mil) meets this threshold. Kraft-faced insulation is Class II (0.1–1.0 perm), unfaced fiberglass has very high permeance and is not a vapor retarder, and standard latex paint is Class III (1.0–10 perms).

Question 3

A homeowner reports recurring efflorescence on an interior concrete block basement wall. This primarily indicates:

Accepted Answer

Active water infiltration carrying soluble salts through the masonry

Answer

Efflorescence forms when water infiltrates masonry, dissolves soluble salts (calcium carbonate, sulfates), and then evaporates on the interior surface, leaving deposits behind. This requires active water movement through the wall, not just surface condensation or paint failure. Freeze-thaw damage and paint aging are separate failure modes that don't produce salt deposits on interior faces.

Question 4

Which of the following is the primary driving force for bulk water intrusion through a below-grade foundation wall?

Accepted Answer

Hydrostatic pressure from saturated soil

Answer

Saturated soil exerts hydrostatic pressure perpendicular to the foundation wall, forcing water through cracks, joints, and porous masonry. Vapor pressure and capillary suction are secondary mechanisms that operate at a much smaller scale; wind-driven rain acts on above-grade surfaces and cannot directly cause below-grade intrusion.

Question 5

Thermal bridging in a wall assembly causes localized cold spots that can lead to mold growth. What building component most commonly creates thermal bridges in wood-framed construction?

Accepted Answer

Wood studs themselves conducting heat out through the wall

Answer

Wood studs extend continuously from the interior to the exterior sheathing, conducting heat out of the wall at a much higher rate than the fiberglass insulation between them. Fiberglass batt is itself the insulating layer, not a bridge; house wrap and interior paint are thin surface materials with negligible thermal conductance.

(CMI) Certified Mold Inspector Practice Test

(CMI) Certified Mold Inspector Practice Test

CMI Moisture Intrusion & Building Science 2