What is the default attic ventilation area requirement?

The default attic ventilation area requirement being 1 square foot for every 150 square feet of attic space is established to ensure proper air circulation and moisture control within the attic. This standard is grounded in building codes and guidelines that aim to maintain a balance of air within the attic space, helping to prevent issues such as mold growth, ice dam formation in colder climates, and excessive heat buildup during warmer months.

Adequate ventilation allows for the exchange of stale, humid air with fresh air, thereby maintaining appropriate humidity levels and improving energy efficiency by reducing the amount of heat that can be trapped in the attic. The 1:150 ratio reflects a balance between enough space for moisture to escape while keeping the attic well-ventilated in accordance with the typical building designs.

In contrast, the other choices would not provide sufficient ventilation based on standard guidelines, potentially leading to adverse conditions in the attic space. It is crucial to adhere to the correct ratio to ensure optimal attic performance and longevity of roofing and insulation materials.