Which of the following scenarios in a typical Canadian residential wood-frame construction would most likely lead to condensation within the wall assembly if the vapour barrier is incorrectly placed?

Question: Which of the following scenarios in a typical Canadian residential wood-frame construction would most likely lead to condensation within the wall assembly if the vapour barrier is incorrectly placed?

Answer options: ✅ Vapor barrier installed on the exterior side of the exterior sheathing in a cold climate.

• Vapor barrier installed as the innermost layer, directly behind the drywall, in a cold climate.
• Vapor permeable air barrier installed on the exterior side of the exterior sheathing in a cold climate.
• No vapor barrier installed, only a continuous air barrier on the interior side, in a warm climate.

Correct answer: Vapor barrier installed on the exterior side of the exterior sheathing in a cold climate.

Explanation: Installing a vapour barrier on the cold side (exterior) of the wall in a cold climate traps moisture that has migrated through the wall from the warm interior. When this warm, moist air meets the cold vapour barrier, it condenses, leading to potential mould and decay issues within the assembly.