The perfect wall has four control layers outside of the structure:
- a water control layer
- an air control layer
- a vapor control layer
- a thermal control layer
Figure 2: Typical Perfect Wall—The most common manifestation of the perfect wall is a steel framed wall sheathed with exterior gypsum board. Note the vapor profile at the bottom. Drying occurs to the interior from the bold line and to the exterior from the bold line in all climates.