What is the primary purpose of the building skin?

The primary purpose of the building skin is to protect the underlying materials. The building skin serves as the first line of defense against environmental factors such as weather, moisture, and temperature changes, thereby ensuring the integrity and longevity of other components within the structure. It helps to shield insulation, structural elements, and mechanical systems from potential damage caused by exposure to rain, wind, snow, and sun.

While reducing heat gain and improving vapor flow resistance are important considerations in building design, they are secondary functions that contribute to overall energy efficiency and comfort rather than the primary function of protection. Maintaining the depressurization limit is related to indoor air quality and pressure management rather than the main role of the building skin itself. Thus, the correct choice emphasizes the fundamental protective role that the building skin plays in preserving the health and durability of the entire building assembly.