In a cold climate wall, what is the interior-most layer?

In a cold climate wall, what is the interior-most layer?

• A. Interior finish
• B. Vapor barrier
• C. Insulation
• D. Cladding

Answer: (A)

The most interior layer is the interior finish. This is the finished surface that faces the living space (like drywall or plaster), forming the boundary inside the building. In cold-climate wall assemblies, the layers run from interior to exterior: interior finish, then moisture-control and/or other interior-facing components, followed by insulation in the wall cavity, and finally the exterior cladding. The insulation and cladding sit outside the interior finish, so the interior finish remains the innermost boundary. The other options serve important roles (vapor control, heat insulation, exterior protection) but they are not the inside-facing surface.

The most interior layer is the interior finish. This is the finished surface that faces the living space (like drywall or plaster), forming the boundary inside the building. In cold-climate wall assemblies, the layers run from interior to exterior: interior finish, then moisture-control and/or other interior-facing components, followed by insulation in the wall cavity, and finally the exterior cladding. The insulation and cladding sit outside the interior finish, so the interior finish remains the innermost boundary. The other options serve important roles (vapor control, heat insulation, exterior protection) but they are not the inside-facing surface.