Attic Ventilation Needs

How to determine whether you need better attic ventilation.

Attic ventilation needs.

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. He has calculated that he needs 7 36 square feet of ventilation space for his attic. Feet of attic space divided 50 50. Intake vents located at the lowest part of the roof under the eaves allow cool.

The following are the requirements taken directly from the irc. In the winter warm moist air seeps into the attic from the living space below. Good ventilation allows the heat and moisture to escape. 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 cuts cooling costs and prolongs shingle life. His next step is to calculate the total amount of ventilation that he has in his attic. Throughout the balance of this digest the terms attic and roof will and can be used interchangeably. That said air resistance and interference such as vent grates reduces the area of true ventilation.

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. 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. Foot of ventilation for every 150 sq. Enter square footage calculate or enter the square footage of the attic or area to be vented.

In the summer good attic ventilation reduces heat buildup. The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. In other words the entire vent opening doesn t count as vented space. 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.

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. His home is 48 feet long and has a ridge vent that measures 46 feet.