What is the minimum requirement for attic ventilation?

The minimum requirement for attic ventilation is determined by the need to maintain proper airflow to prevent moisture buildup, reduce heat, and prolong the lifespan of the roofing materials. According to the International Building Code (IBC) and International Residential Code (IRC), the standard ratio for attic ventilation is 1 square foot of net free ventilating area (NFVA) for every 300 square feet of attic floor area.

This ratio is designed to balance the intake and exhaust of air within the attic space. Proper ventilation helps to ensure that the attic remains cool in the summer and minimizes the risks of ice dams in winter. A ventilation ratio of 1 in 300 sq ft effectively controls heat and moisture, thus addressing potential issues that could arise from inadequate ventilation.

The other options reflect ventilation ratios that are either too generous or not in line with the regulatory standards for residential buildings. Therefore, a ratio of 1 in 300 sq ft is recognized as the established minimum requirement for attic ventilation.