Focus on ventilation

Roof ventilation issues can be resolved by meeting standards

As buildings have become tighter, a variety of issues related to roof ventilation—including ice damming, water condensation and mold within the building envelope—have tormented owners and contractors with increasing regularity. Many of these issues have manifested as costly court battles and insurance claims resulting in the general public's heightened awareness of these concerns and increased accountability in the contracting community.

Professional roofing contractors have a distinct role to play to ensure ventilation standards are met—primarily at the ridge.


The ventilation standard is specified in the 2003 International Residential Code (IRC) Sect. R806. For roof areas over heated or conditioned spaces, a net-free ventilation area of 1 square foot per 150 square feet (67 cm²/1 m²) of ceiling area is required. This can be simplified by rounding the equation to 1 square inch of ventilation per square foot of ceiling.