Ventilation Calculator
Calculate required attic ventilation for your home
Enter Attic Information
Calculate the proper ventilation needed for your attic space
Measure the floor area of your attic (same as your home's square footage for single-story homes)
Most areas fall in moderate climate zones, with regional variations
Enter your attic area to calculate ventilation requirements
Understanding Attic Ventilation
Why Proper Ventilation Matters
- Prevents moisture buildup and mold growth
- Extends roof life by reducing heat damage
- Improves energy efficiency by reducing cooling costs
- Prevents ice dams in winter
The 1:150 Rule
Building codes require 1 square foot of net free area (NFA) for every 150 square feet of attic space. This should be split 50/50 between:
- Intake vents: Soffit vents at the eaves
- Exhaust vents: Ridge vents or roof vents
Important: Net Free Area (NFA) is the actual open area of a vent after accounting for screens and louvers. Always check the NFA rating when purchasing vents, as it's typically 50-70% of the vent's total size.
Need Professional Ventilation Assessment?
Get a free attic inspection from Top Guys Roofing. We'll assess your current ventilation and recommend improvements to protect your roof and home.