BPI Multifamily Building Analyst Practice Exam - Prep, Practice Questions, and Study Guide

Fiberglass insulation does not impede the flow of air significantly. It is designed to create thermal resistance by trapping air within its fibrous structure, but it does not form a continuous air barrier. This means that while it provides effective insulation, it allows for some air movement, which is important for ventilation purposes.

In contrast, dense cellulose insulation, spray foam insulation, and mineral wool insulation generally create tighter seals within building assemblies. Dense cellulose, for instance, can settle over time and may inhibit airflow more than fiberglass. Spray foam insulation expands upon application, filling gaps and providing an airtight seal, which can completely obstruct airflow. Mineral wool insulation is also denser and can block air movement more effectively than fiberglass.

Understanding how different insulation types interact with airflow is critical for achieving optimal energy performance and indoor air quality in multifamily buildings.