What is a significant reason for the downward trend in air leakage requirements?

The significant reason for the downward trend in air leakage requirements can be attributed to the realization of the impact of air leakage on moisture management. This understanding emphasizes that uncontrolled air leakage can lead to a range of issues, such as condensation, mold growth, and deterioration of building materials. As the awareness of these problems has grown, it has prompted the development of stricter standards and requirements for air barrier systems to ensure better moisture control within buildings. Recognizing the relationship between air leakage and moisture management is critical for promoting healthier indoor environments and enhancing the durability and performance of structures over time.

The other choices, while they may touch on relevant aspects of the construction industry, do not directly correlate to the specific reason behind the trend in air leakage requirements. Building material costs and architectural design preferences are important factors in construction but do not have the same direct connection to the moisture management issues that arise from air leakage. Similarly, while worker training improvements can lead to better installation practices, they do not fundamentally address the underlying reasons for evolving air leakage standards.