Attic Ventilation Needs

Feet of attic space divided 50 50.

Attic ventilation needs.

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. That said air resistance and interference such as vent grates reduces the area of true ventilation. Throughout the balance of this digest the terms attic and roof will and can be used interchangeably. Enter square footage calculate or enter the square footage of the attic or area to be vented.

Generally speaking you need a ratio of 1 300 where for every 300 square feet of ceiling space you need 1 square foot of attic ventilation. 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. Foot of ventilation for every 150 sq. In the winter warm moist air seeps into the attic from the living space below.

His home is 48 feet long and has a ridge vent that measures 46 feet. His next step is to calculate the total amount of ventilation that he has in his attic. Intake vents located at the lowest part of the roof under the eaves allow cool. Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.

The majority of the requirements related to attic ventilation have not changed much from the previous editions. How to determine whether you need better attic ventilation. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. The following are the requirements taken directly from the irc.

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 the summer good attic ventilation reduces heat buildup. Good ventilation allows the heat and moisture to escape. That cuts cooling costs and prolongs shingle life.

He has calculated that he needs 7 36 square feet of ventilation space for his attic. In cold climates the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow and to vent moisture that moves from the conditioned space to the attic ventilation acts to bypass the vapour barrier created by most roof.