In a cold climate wall, what is the correct order of layers from interior to exterior?

• A. Interior finish, insulation, vapor barrier, cladding and sheathing
• B. Vapor barrier, interior finish, insulation, sheathing and cladding
• C. Interior finish, vapor barrier, insulation, sheathing and cladding
• D. Interior finish, insulation, cladding, vapor barrier

Answer: (C)

In cold climates, moisture control relies on placing a vapor barrier on the warm side of the insulation. That keeps interior humidity from diffusing into the insulation and wall cavities where it could condense.

From inside to outside, the sequence is interior finish, then the vapor barrier directly behind it, followed by the insulation, then the sheathing, and finally the exterior cladding. This arrangement keeps the insulation drier, reduces condensation risk, and still allows outward drying through the exterior layers. Placing the vapor barrier after the insulation or on the exterior side would let interior humidity penetrate the insulation and potentially condense within the wall.