BPI Moisture Management 3 — Questions and Answers
Question 1: What term describes the movement of liquid water through a porous material driven by capillary action?
- Vapor diffusion
- Capillary suction (Correct answer)
- Convective moisture transport
- Sorption isotherm
Correct answer: Capillary suction
Capillary suction (capillary rise) is the movement of liquid water through pores driven by surface tension and adhesion forces.
Question 2: Which material property BEST describes a material's ability to absorb and release moisture to buffer indoor humidity levels?
- Permeability
- Hygroscopicity (Correct answer)
- Porosity
- Vapor resistance
Correct answer: Hygroscopicity
Hygroscopicity describes how readily a material absorbs and releases moisture from the air, acting as a humidity buffer.
Question 3: During a BPI assessment, a technician measures 70% relative humidity in a basement at 65°F. What is the MOST appropriate immediate recommendation?
- Install additional foundation vents
- Seal air leaks from outdoors and add dehumidification (Correct answer)
- Increase the heating setpoint to 75°F
- Apply interior waterproof coating to walls
Correct answer: Seal air leaks from outdoors and add dehumidification
High basement RH is primarily controlled by sealing air pathways bringing humid outdoor air in, combined with mechanical dehumidification.
Question 4: What is the primary moisture risk associated with spray polyurethane foam (SPF) applied to the interior of a basement wall?
- SPF reduces the wall's drying potential to the interior (Correct answer)
- SPF increases capillary moisture transfer
- SPF raises the vapor permeance of the assembly
- SPF promotes condensation on the exterior face
Correct answer: SPF reduces the wall's drying potential to the interior
Closed-cell SPF on the interior blocks moisture from drying inward, potentially trapping moisture in the concrete or masonry wall.
Question 5: Which window condition BEST indicates that indoor relative humidity is consistently too high in winter?
- Frost on exterior glazing surfaces
- Condensation on the interior pane of double-pane windows (Correct answer)
- Condensation forming on the exterior frame
- Visible gaps at the window frame
Correct answer: Condensation on the interior pane of double-pane windows
Interior condensation on double-pane windows signals that indoor RH is high enough to reach the dew point at the cold glass surface.
Question 6: What is the purpose of a capillary break between a concrete foundation wall and wood sill plate?
- To improve thermal performance of the sill
- To prevent liquid water wicking from concrete into the wood (Correct answer)
- To meet fire separation requirements
- To allow differential movement between materials
Correct answer: To prevent liquid water wicking from concrete into the wood
A capillary break (such as sill seal foam or a gasket) stops liquid water from wicking up from the porous concrete into the wood sill plate.
Question 7: In mixed-humid climates, which vapor retarder strategy is considered MOST flexible for managing seasonal moisture drive reversal?
- 6-mil polyethylene on the interior
- Variable-permeance (smart) vapor retarder (Correct answer)
- Exterior rigid foam with no interior retarder
- Foil-faced insulation on all wall surfaces
Correct answer: Variable-permeance (smart) vapor retarder
Variable-permeance smart retarders tighten in dry conditions and open up in humid conditions, accommodating seasonal moisture drive reversals.
BPI Moisture Management 3
What term describes the movement of liquid water through a porous material driven by capillary action?