Every 3 years the International Residential building Code (IRC) releases code updates. 2018 is a cycle year. Below is the attic ventilation section. Key notes/changes:
- The minimum amount of attic ventilation remains 1/150 (1 square foot of Net Free Area for every 150 square feet of attic floor space. Attic floor is defined as length x width FLOOR of the attic).
- The amount of ventilation can be reduced to 1/300 (in effect 50% less) BUT 2 conditions must be met effective 1.1.18. Previously only 1 condition had to be met. The ARMA Ventilation Task Force pushed the IRC for this change. (See below).
- Renewed for 2018 is the requirement that “vents must be installed according to the vent manufacturer.” This includes: Don’t Mix Exhaust, give the exhaust vent proper intake, etc.