For warm climates, installing an interior vapor retarder can create a substantial risk of condensation within the wall assembly. A common unintentional example of this is the use of vinyl wallpaper. The vinyl wallpaper acts as an interior vapor retarder and in combination with inward vapor drive can lead to moisture accumulation within the wall assembly. Alternatively, in warm climates where air conditioning is provided, diffusion occurs primarily from the exterior to the interior and an exterior vapor retarder such as an impermeable self-adhered membrane, rigid foam-plastic insulation (i.e. XPS, medium density sprayfoam, etc.) or concrete should be provided. The following two figures show the effect of an exterior vapor retarder versus an interior vapor retarder for a stud insulated wall assembly in a warm climate.