Influence of driving rain on the hygrothermal behavior of solid brick walls

• The wetting and drying phase periods vary according to the adopted climate.
• WDR is responsible for lower exterior heat flux, except for temperatures below 0 °C.
• WDR is responsible for higher interior heat flux.
• The hygrothermal behavior of solid brick walls is highly influenced by WDR.

The purpose of this paper is to identify the changes generated by wind-driven rain in high capillary water uptake walls (such as uncoated solid brick walls) in maritime climates, using for this purpose two cities in different continents with roughly the same latitude – Lisbon (Portugal) and San Francisco (USA), and another further north – Montreal (Canada). The analyzed hygrothermal parameters were the following: solid brick water content; exterior and interior surface heat flux; and exterior and interior surface moisture flux. The paper also analyses the hygrothermal changes caused by the increase of solid brick layer in the exterior capillary flux and thermal transmittance. This study supports the notion that wind-driven rain is one of the main sources of moisture in high capillary water uptake walls, and that wetting/drying cycle varies according to the climate. It was also proven that wind-driven rain is responsible for both a lower exterior heat flux, except when temperatures reach values below the freezing point, and a higher interior heat flux. It was verified that the capillary flux decreases with the increase of thickness whenever the exterior surface reaches its free water saturation. Lastly, it was observed that the difference between calculating a thermal transmittance in steady-state and in transient conditions increases with the increase of solid brick thickness.