Attic Venting Requirements Irc

Ibc 1203 2 requires 1 150 th of the attic area to be ventilated but there is an exception that is commonly used instead.

Attic venting requirements irc.

The minimum net free ventilating area shall be 1 150 of the area of the. The amount of attic cavity ventilation is specified by numerous ratios of free vent area to insulated ceiling area ranging from 1 150 to 1 600 depending on which building code is consulted the 1 300 ratio being the most common. The minimum net free ventilating area shall be 1 150 of the area of the vented space. R806 2 minimum vent area.

The following product options will allow you to achieve an intake nfva of 528 square inches. This article will not discuss them but readers are encouraged to familiarize themselves with those requirements. Every 3 years the international residential building code irc releases code updates. Requirements for unvented attics can be found in section r806 5 of the 2018 irc.

This section contains an extensive list of requirements and conditions that have to be met in order to have an unvented attic. Attic ventilation shall not be required when determined not necessary by the code official due to atmospheric or climatic conditions. Not less than 40 percent and not more than 50. 2018 is a cycle year.

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. The example below uses this exception and the calculation is based on a. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.

The minimum net free ventilation area shall be 1 300 of the vented space provided one or more of the following conditions are met. The requirements of section r802 7. Below is the attic ventilation section. Required ventilation openings shall open directly to the outside air.

In climate zones 14 and 16 a class i or ii vapor retarder is installed on the warm in winter side of the ceiling. Allows cool dry air to enter the attic.