Thermal Patters Due to Moisture Accumulation within Exterior Walls
In cold climates, air leakage is accompanied by moisture transport. When migrating through dew point temperatures, a considerable amount of moisture accumulation may occur depending on variables such as the duration of sub-zero exterior temperatures, building pressurization, wind effects and the level of interior relative humidity. Moisture accumulation may result in premature deterioration of wall assemblies and the formation of mold. When commissioning new building envelopes, or carrying out building condition inspections of existing building envelopes, it is imperative to differentiate the source of the moisture accumulation since the recommendation for remedial action will vary considerably. This paper will define the various types of thermal patterns created by surface penetration of water versus those patterns created by air leakage from the building interior in cold winter conditions. Various types of exterior building envelopes will be discussed along with their hygro-thermal performance characteristics and how these affect thermal patterns during various inspection procedures.