1. What is the Attic Ventilation Calculation?

The attic ventilation calculation determines the minimum required vent area based on attic square footage. The general rule is 1 square foot of vent area per 150 square feet of attic space.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• Attic Sq Ft — Total square footage of attic space
• 150 — The ratio of attic area to vent area

Explanation: This calculation ensures proper air circulation to prevent moisture buildup and regulate temperature in the attic space.

3. Importance of Proper Attic Ventilation

Details: Adequate attic ventilation helps prevent ice dams in winter, reduces cooling costs in summer, prevents moisture damage, and extends roof life.

4. Using the Calculator

Tips: Measure your attic's floor area (length × width) and enter the total square footage. The calculator will determine the minimum vent area needed.

5. Frequently Asked Questions (FAQ)

Q1: Why the 1:150 ratio?
A: This is the minimum requirement in most building codes for balanced ventilation (intake and exhaust).

Q2: Can I have too much ventilation?
A: Excessive ventilation can cause problems in cold climates by allowing warm, moist air to escape too quickly.

Q3: What types of vents should I use?
A: A combination of soffit vents (intake) and ridge vents (exhaust) is typically most effective.

Q4: Does this apply to cathedral ceilings?
A: Cathedral ceilings require different ventilation approaches - consult a roofing professional.

Q5: Should vent area be split between intake and exhaust?
A: Yes, the total vent area should be balanced between intake (typically at the eaves) and exhaust (typically at the ridge).