Attic Venting Requirements Irc

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.

Attic venting requirements irc.

The following product options will allow you to achieve an intake nfva of 528 square inches. The minimum net free ventilating area shall be 1 150 of the area of the. 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. 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.

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. 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. In climate zones 14 and 16 a class i or ii vapor retarder is installed on the warm in winter side of the ceiling. Required ventilation openings shall open directly to the outside air. 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 requirements of section r802 7. Allows cool dry air to enter the attic. 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 ventilation area shall be 1 300 of the vented space provided one or more of the following conditions are met.

Below is the attic ventilation section. The minimum net free ventilating area shall be 1 150 of the area of the vented space. The example below uses this exception and the calculation is based on a. R806 2 minimum vent area.

Ibc 1203 2 requires 1 150 th of the attic area to be ventilated but there is an exception that is commonly used instead. Choose one of the following products to meet the recommended intake nfva of 528 square inches.