This is critical to pay attention too.
Structure (priority 1)
Supports the remainder of the wall, floor, or roof.
Substrate (priority 2)
Consists of materials such as plywood or gypsum board, which act as a foundation for another layer.
Thermal/Air layer (priority 3)
Provides insulation and prevents air penetration.
Prevents water vapor penetration. The membrane layer should have zero thickness.
Finish 1 (priority 4)
Used as the exterior layer.
Finish 2 (priority 5)
Used as the interior layer.