Attic Space Venting Requirements

Requirements for unvented attics can be found in section r806 5 of the 2018 irc.

Attic space venting requirements. Proper attic ventilation can be an impor tant performance consideration when design ing and installing steep slope roof systems. Prior to installing the ridge vent a 1 inch wide strip of roof decking is cut out along both sides of the ridgeline to allow for air movement through the. Hence you would need two square feet 600 300 of attic ventilation. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation.

The roofing industry also has practical guide lines for attic ventilation. In order to find the right calculator divide the attic floor. Calculate the square footage of the attic space. The following product options will allow you to achieve an intake nfva of 528 square inches.

Result of item 1 300. It really is a design choice. 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. This section contains an extensive list of requirements and conditions that have to be met in order to have an unvented attic.

According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space. Calculating attic ventilation requirements. Choose one of the following products to meet the recommended intake nfva of 528 square inches. Building codes typically require 1 square foot of venting space for every 150 square feet of attic space.

Code requirements the international building code. If the attic is equipped with high and low ventilation openings the requirement is 1. Divide the square footage item 1 by 300. Typically building codes include minimum requirements applicable to attic ventilation.

Calculate net free vent 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. So the decision to vent an attic space is not dictated by building code. Intake vents located at the lowest part of the roof under the eaves allow cool.

There should also be a 50 50 balance of attic venting and roof venting. The two square feet is divided equally between the intake and the exhaust one square foot for each. The venting space should be equally divided between intake. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

Allows cool dry air to enter the attic.