Most present day low and medium rise buildings constructed in Canada use some form of cavity wall design for their exterior walls. These types of wall assemblies use a broad range of cladding materials such as brick, stone, wood, sheet metal, porcelain enamel or metal panels, cementitious materials and plastics. The interior assemblies of these walls include the air barrier, vapor barrier and insulation layers. The cladding is separated from the interior wall assembly by an air space of varying thickness. Dependent upon the temperature differential between the interior and exterior, the temperature between the outer surface of the interior wall assembly and the inner surface of the exterior cladding under conditions in which air movement is restricted will give rise to convective heat loss mechanisms. This paper will look at how these convective heat loss patterns manifest themselves as thermal patterns on exterior surfaces of cladding materials. Similar details will be illustrated under various pressure differential conditions through the entire building envelope assembly. Various types of exterior wall assemblies will be discussed.