What percentage of free air is required for metal louvers?

The requirement that metal louvers provide a certain percentage of free air is related to ensuring proper ventilation and air movement in a building or space. Achieving 75% free air means that the louver must allow for three-quarters of its opening to remain unobstructed to air flow when closed or partially opened, ensuring adequate ventilation.

This level of free area in metal louvers contributes to efficiency in air distribution, contributing to the overall HVAC system performance. It allows enough fresh air to enter while also enabling exhaust when necessary. If the free area were lower, it could hinder airflow, potentially leading to pressure buildup and inefficiencies in heating or cooling processes.

Understanding the importance of this percentage is crucial for maintaining indoor air quality and energy efficiency in plumbing and HVAC designs, which is why 75% is the accepted standard in many codes and practices.