Attic Ventilation Required

Hence you would need two square feet (600 ÷ 300) of attic ventilation.

Attic ventilation required.

The required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Federal housing authority recommends a minimum of 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space. As an example, in an attic that is 30 feet by 20 feet you would have 600 square feet of floor area.

Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. A raised top plate increases the area for insulation and ventilation. Current regulations state that the minimum attic ventilation requirements are 150/1.

Exterior openings into the attic space of any building intended for human occupancy shall be protected to prevent the entry of birds, squirrels, rodents, snakes and other similar creatures. The minimum amount of attic ventilation remains 1/150 (1 square foot of net free area for every 150 square feet of attic floor space. If your attic floor has a vapor barrier, you will need one square foot of nfa per every 300 square feet of attic floor area (half of that will be intake, half for exhaust).

According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space. The amount of ventilation can be reduced to 1/300 (in effect 50% less) but 2 conditions must be met effective 1.1. Some experts also question whether ventilation is effective at moisture removal.

170° roof sheath temperature 140° attic temperature 115° attic temperature 4 section 1:hows and whys of attic ventilation However, since the 2009 edition of the irc, attics can be designed to be either vented or unvented. This means that if you have a 1500 sqattic then you would need at least 10 sfof ventilation.

Common misconceptions attic ventilation always removes moisture vapor during cold weather. Attic floor is defined as length x width floor of the attic). If the attic is separated or segmented (as if with a wall), each separate section should be ventilated.