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.

Below is the attic ventilation section. 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. 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. This article will not discuss them but readers are encouraged to familiarize themselves with those requirements.

This section contains an extensive list of requirements and conditions that have to be met in order to have an unvented attic. The requirements of section r802 7. The following product options will allow you to achieve an intake nfva of 528 square inches. Attic ventilation shall not be required when determined not necessary by the code official due to atmospheric or climatic conditions.

Exception 1 allows you to only ventilate 1 300 th of the attic area if 50 to 80 of the ventilation occurs at least 3 above eave or cornice vents. Requirements for unvented attics can be found in section r806 5 of the 2018 irc. 2018 is a cycle year. Not less than 40 percent and not more than 50.

The example below uses this exception and the calculation is based on a. The minimum net free ventilating area shall be 1 150 of the area of the. The international residential code 2012 edition irc 2012 contains requirements similar to ibc 2012 except irc 2012 limits the net free ventilation reduction from 1 150 to 1 300 when at least 40 percent but no more than 50 percent of the required venti lation area is provided at or near the upper portion of the space being ventilated. 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.

R806 2 minimum vent area. Allows cool dry air to enter the attic. In climate zones 14 and 16 a class i or ii vapor retarder is installed on the warm in winter side of the ceiling. The minimum net free ventilating area shall be 1 150 of the area of the vented 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. Every 3 years the international residential building code irc releases code updates.