Attic Air Ventilation Requirements

Of vent for every 300 sq.

Attic air ventilation requirements.

Does an attic have to be vented. Calculate or enter the square footage of the attic or area to be vented. The insulation will resist heat transfer into the house. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

Building codes vary. As an example in an attic that is 30 feet by 20 feet you would have 600 square feet of floor area. What does the code require. Attic ventilation serves two main functions.

Measure the length and width of the attic floor space to be ventilated. Enter your square footage. 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. According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space.

There should also be a 50 50 balance of attic venting and roof venting. In the summer natural air flow in a well vented attic moves super heated air out of the attic protecting roof shingles and removing moisture. Balance is the key. Most building codes require a ratio of 1 150 ventilation space to attic floor space.

To lower attic temperatures and to remove excess moisture. Hence you would need two square feet 600 300 of attic ventilation. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Proper insulation and air sealing also keeps attics cold in winter by blocking the entry of heat and moist air from below.

Basic attic ventilation principal is to keep that unused section of our house as cool as possible critical condition during the cold season dividing amount of the roof upper and lower vents 50 50. According to the fha federal housing administration us for every 300 square feet of attic floor area you should have at minimum one square foot ventilation. Vents are rated by their net free area or the amount of space for air to flow in or out.