What is the recommended ventilation formula for an attic?

The correct answer highlights the importance of proper attic ventilation in maintaining appropriate temperature and moisture levels within the attic space. The recommended formula of 1 square foot of free vent area for every 150 square feet of attic floor effectively balances air intake and exhaust, which is crucial for optimal ventilation.

This ratio allows for sufficient airflow to help prevent issues such as heat buildup during warmer months and condensation during colder months. Adequate ventilation can mitigate problems like roof deterioration, ice dam formation, and structural damage caused by trapped moisture.

Choosing a higher ratio, such as 1 square foot per 50 or 100 square feet of attic floor space, would provide more vent area than necessary, which might not be ideal and could lead to reduced performance. Conversely, using a lower ratio, such as 1 square foot for every 200 square feet, could result in inadequate ventilation and invite similar moisture and heat issues.

Therefore, the ratio of 1 square foot of free vent area for each 150 square feet strikes a balance that effectively promotes ventilation without being excessive, making it the recommended standard in building practices.