In commercial construction, another type of wall is also commonly used; architectural or exposed concrete, or in some cases concrete masonry units (CMU). These walls are insulated on the interior and create a different situation than the other types of walls discussed. The figures below show these types of walls for cold and hot climate.

Exposed concrete and CMU create a vapor retarder on the exterior of the wall assembly, which works well for warm climates where the primary vapor drive is inward. The concrete will restrict the flow of vapor through the assembly and consequently prevent condensation and high humidity levels within the assembly. The image below illustrates this schematically.

Using a vapor permeable insulation on the interior of concrete walls in warm climates can also allow any incidental moisture to dry to the interior. By comparison, an impermeable insulation product would restrict drying to the interior.

In cold climates, the exterior vapor retarder created by the concrete means a risk of condensation within the assembly. Additionally, as this would typically be installed with an interior vapor retarder in a cold climate, a double vapor barrier situation is created, which limits drying.

The following figure illustrates an exposed concrete wall with batt insulation and a poly vapor barrier on the interior. This approach is not recommended as it creates a double vapor barrier.

A number of alternative methods exist for insulating these types of walls in cold climates. Spray polyurethane foams can be applied directly to the concrete, CMU or precast, or in some cases taped XPS or polyisocyanurate insulation could also be used. In both cases the insulation provides vapor control and an air barrier so that air does not leak from the interior and condense on the back of the concrete. In some cases, using a smart vapor retarder instead of poly sheet may also reduce the risk associated with interior insulated concrete assemblies.

Generally, exposed concrete or CMU walls provide robust durability in warm climates, but can provide some challenges when used in cold climates.