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1. What is the primary purpose of a vapor barrier in a building
assembly?
A. Improve sound insulation
B. Reduce energy usage
C. Control moisture migration
D. Protect against UV exposure
Correct answer: C — Vapor barriers are installed to slow or stop
moisture vapor movement through building assemblies.
2. Which material is most commonly used as a vapor barrier in
residential construction?
A. Asphalt felt
B. Plywood
C. Polyethylene sheeting
D. Cement board
Correct answer: C — Polyethylene is widely used due to its low
permeability.
3. Vapor barrier effectiveness is measured by its:
A. Temperature rating
B. UV resistance
C. Perm rating
D. Fire resistance
, Correct answer: C — The perm rating measures resistance to
vapor transmission.
4. A vapor retarder with a perm rating less than or equal to 0.1 perms
is classified as:
A. Class I
B. Class II
C. Class III
D. Class IV
Correct answer: A — Class I vapor retarders are 0.1 perms or less.
5. Where should a vapor barrier typically be placed in a cold
climate?
A. Exterior face of insulation
B. Interior/warm side of insulation
C. Middle of the wall assembly
D. On both sides of insulation
Correct answer: B — Prevents warm interior moisture from
migrating into cold spaces.
6. Installing vapor barriers on both sides of a wall can cause:
A. Fire hazards
B. Moisture trapping and mold growth
C. Noise issues
D. Structural instability
Correct answer: B — Two vapor barriers can trap moisture inside
assemblies.
7. The continuity of a vapor barrier is most often compromised
by:
A. Paint
B. Concrete curing
, C. Penetrations and unsealed seams
D. Insulation density
Correct answer: C — Holes and gaps significantly reduce
effectiveness.
8. Which tape is recommended for sealing polyethylene vapor
barriers? A. Duct tape
B. Masking tape
C. Cloth tape
D. Acrylic-based vapor barrier tape
Correct answer: D — Acrylic tape maintains long-term adhesion.
9. A vapor barrier is required under concrete slabs primarily to
prevent: A. Odor migration
B. Soil shifting
C. Moisture vapor movement from the ground
D. Cold temperatures
Correct answer: C — Vapor barriers beneath slabs stop ground
moisture migration.
10. Which of the following is a Class I vapor barrier?
A. Kraft paper
B. 6-mil polyethylene
C. Latex paint
D. Unfaced insulation
Correct answer: B — Poly sheeting is a Class I vapor barrier.
11. Under-slab vapor barriers should be a minimum of:
A. 2 mils
B. 4 mils