Roof Ventilation Calculator
Calculate proper attic ventilation using the 1:150 or 1:300 rule. Size ridge vents, soffit vents, and exhaust vents for optimal airflow.
Enter Your Attic Details
Roughly equal to your home's footprint
For ridge vent sizing (leave blank if unknown)
Enter Your Attic Details
Input your attic size and current ventilation to get precise vent sizing recommendations for optimal airflow.
Frequently Asked Questions
How much ventilation does my attic need?
The standard requirement is 1 square foot of Net Free Area (NFA) for every 150 square feet of attic floor space (1:150 rule). If you have a vapor barrier and balanced venting, you can use the 1:300 rule. For a typical 1,500 sq ft home, you need about 1,440 square inches of total ventilation, split between intake and exhaust vents.
Can I mix ridge vents with other exhaust vents?
It's best not to mix ridge vents with power vents or turbine vents. They can short-circuit each other's airflow. Ridge vents work best when paired only with soffit vents. If you have gable vents, consider sealing them when adding a ridge vent system for optimal performance.
Why is intake ventilation so important?
Without adequate intake (soffit) vents, exhaust vents can't function properly. They may even draw conditioned air from your living space through ceiling gaps, wasting energy. The best systems have equal or greater intake than exhaust. In fact, slightly more intake than exhaust creates positive pressure that improves airflow.
Will more ventilation make my home colder in winter?
Properly installed attic ventilation doesn't significantly affect winter heating costs because the thermal barrier (insulation) should be at the attic floor, not the roof. Ventilation actually helps in winter by removing moisture that could condense and cause damage. The key is having good insulation below the vented attic space.
How do I know if my attic ventilation is inadequate?
Signs of poor ventilation include: extremely hot upstairs rooms in summer, moisture/frost on attic surfaces in winter, peeling exterior paint near roofline, musty odors in attic, wavy or rippled shingles, and ice dams (in cold climates). If your attic feels significantly hotter than outside air temperature, ventilation is likely insufficient.
Need Professional Ventilation Assessment?
Our roofing experts can inspect your attic ventilation and recommend the best solution for your Myrtle Beach home.