Attic Ventilation Needs

His next step is to calculate the total amount of ventilation that he has in his attic.

Attic ventilation needs.

His home is 48 feet long and has a ridge vent that measures 46 feet. 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. That said air resistance and interference such as vent grates reduces the area of true ventilation. 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.

The following are the requirements taken directly from the irc. In the summer good attic ventilation reduces heat buildup. 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 works on the principle that heated air naturally rises primarily utilizing two types of vents.

The majority of the requirements related to attic ventilation have not changed much from the previous editions. The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. Foot of ventilation for every 150 sq. Your soffit ventilation actually needs to be considerably more than 336 net square inches to supply a 700 cfm fan system or the fan is going to pull the air it needs through unsealed holes and gaps in the attic floor from the conditioned living space.

Feet of attic space divided 50 50. That cuts cooling costs and prolongs shingle life. In other words the entire vent opening doesn t count as vented space. Intake vents located at the lowest part of the roof under the eaves allow cool.

In the winter warm moist air seeps into the attic from the living space below. Enter square footage calculate or enter the square footage of the attic or area to be vented. 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.

How to determine whether you need better 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.