Attic Air Ventilation Requirements

The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation.

Attic air ventilation requirements.

What does the code require. To lower attic temperatures and to remove excess moisture. Of vent for every 300 sq. Does an attic have to be vented.

Attic ventilation serves two main functions. Measure the length and width of the attic floor space to be ventilated. 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. Proper insulation and air sealing also keeps attics cold in winter by blocking the entry of heat and moist air from below.

Enter your square footage. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. 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.

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. Most building codes require a ratio of 1 150 ventilation space to attic floor space. Balance is the key.

Hence you would need two square feet 600 300 of attic ventilation. I was told there would be no math. 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. The insulation will resist heat transfer into the house.

There should also be a 50 50 balance of attic venting and roof venting. According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.