How Much Attic Ventilation

To keep air flowing your roof needs just the right amount of attic ventilation.

How much attic ventilation.

Attic fan ventilation 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. 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. 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. Always have a balanced ventilation system.

However if your attic has blocked soffit vents and is not well sealed from the rest of the house attic fans will suck cool conditioned air up out of the house and into the attic. Ventsure inflow intake vent. In other words the entire vent opening doesn t count as vented space. The basic formula for a typical residence is 1 foot of passive vent opening per every 150 square feet of attic size.

That said air resistance and interference such as vent grates reduces the area of true ventilation. We show you how to install soffit vents step by step to improve your attic ventilation. Soffit vents help increase the airflow are easy to install and only cost about 3 per 8 ft. What does the code require.

Choose one of the following products to meet the recommended intake nfva of 528 square inches. Most building codes require a ratio of 1 150 ventilation space to attic floor space. Ideally the total vent space should be equally divided between lower soffit vents and upper vents at the roof peak. Of vent for every 300 sq.

Here s how to install soffit vents step by step to improve the airflow in your attic. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. You can also contact your local municipality to check on building code in your area. Attic ventilation keeps the air moving and stops mold from growing but too much ventilation can be just as bad as having none.

How much attic ventilation is enough. Allows cool dry air to enter the attic. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.