The ratio of 1/150 represents a guideline for determining the minimum amount of net free ventilation area needed in an attic space relative to the insulated ceiling area below. For instance, if an attic has an insulated ceiling area of 1500 square feet, the calculation would suggest a requirement of 10 square feet of net free ventilation area (1500 / 150 = 10). This figure serves as a baseline for ensuring adequate airflow.
Proper attic ventilation, guided by this calculation, is vital for maintaining optimal building performance. It mitigates moisture buildup, which can lead to mold growth and structural damage. Effective airflow regulation also helps to reduce energy costs by minimizing heat gain in the summer and preventing ice dam formation in the winter. Historically, establishing appropriate ventilation levels has been a key factor in preserving the longevity and integrity of residential and commercial buildings.
