Attic Ventilation Required

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.

Attic ventilation required. Attic ventilation requirements how many attic vents your roof needs industry standard for proper attic ventilation recommends for no vapor retarder type of attic insulation no paper plastic or aluminum layer between the attic floor and insulation layer 1 sq. In of vent opening per 150 sq. According to the home ventilating institute hvi powered attic ventilators need to move a minimum of 700 cubic feet per minute cfm for 1 000 sq. Then aim for about 1 sq.

Ft of attic space for example 20 x 50 to be effective. The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. Allows cool dry air to enter the attic. Feet of attic space divided 50 50 between the inlets and outlets.

How many vents do you need. Choose one of the following products to meet the recommended intake nfva of 528 square inches. Foot of ventilation for every 150 sq. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

First determine your attic area by multiplying the length by the width. Intake vents located at the lowest part of the roof under the eaves allow cool. Code requirements the international building code 2012 edition ibc 2012 requires enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing to have cross ventilation for each separate space. The majority of the requirements related to attic ventilation have not changed much from the previous editions.

Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Attic for example has an area of 1 200 sq. A 30 x 40 ft. Ventsure inflow intake vent.

You can calculate attic ventilation requirements by determining the square footage of your attic floor its width times its length and compare that to the total required net free area nfa. Lines for attic ventilation. The net free vent area nfva shall not be less than 1 150 of the area of the space being vented. The following product options will allow you to achieve an intake nfva of 528 square inches.

Vents are rated by their net free area or the amount of space for air to flow in or out. Most building codes require a ratio of 1 150 ventilation space to attic floor space.