Final answer:
A rainscreen wall becomes a pressure-equalized wall when the pressure inside the cavity equals the pressure outside, which reduces the forces that might drive water through the wall assemblies. Option A is correct.
Step-by-step explanation:
A rainscreen wall becomes a pressure-equalized wall when the pressure inside equals the pressure outside. This concept is essential in building design, especially for the envelope or the cladding system of a structure. Pressure equalization aims to prevent water from being driven through the wall assemblies by minimizing the pressure differential across the cladding.
Under normal environmental conditions, the air pressure on the outside of a building can force water into the building through any openings in the exterior wall. A rainscreen system includes a cavity that allows for drainage and evaporation, helping to protect the wall assembly.
However, for it to become pressure-equalized, there must be an opportunity for the air pressure within the cavity to adjust to match the outside pressure, often through the use of ventilation.
Restricted ventilation would not allow this to occur, and therefore is not conducive to pressure equalization. When the air pressures are equal, the forces that might drive water through the wall are greatly reduced, thus improving the wall's resistance to water infiltration.