The required area of openings in exterior walls on a tier in open parking garages must not be less than what percentage of the total perimeter wall area of each tier?

The required area of openings in exterior walls on a tier in open parking garages is specified to be at least 20% of the total perimeter wall area of each tier. This requirement is primarily related to ensuring proper ventilation and air circulation within the parking structure. Adequate openings help reduce the buildup of harmful gases, such as carbon monoxide, which can accumulate in enclosed areas due to vehicle emissions.

This percentage is established based on building codes and safety regulations that aim to maintain air quality and safety standards within these types of structures. By ensuring that at least 20% of the wall area consists of openings, the design supports sufficient airflow, which is critical in mitigating the risks associated with vehicle exhaust and maintaining a safe environment for users of the parking facility.

In contrast, other percentages, such as 10%, 30%, or 40%, do not align with the established standards for this type of building. A lower percentage like 10% might not provide adequate ventilation, while higher percentages like 30% or 40% could be unnecessarily excessive, impacting the structural integrity or the intended functionality of the garage without adding a significant benefit. Thus, the 20% requirement strikes a balance between safety and practical design considerations.