How Much Attic Ventilation Is Enough

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

How much attic ventilation is enough.

The basic formula for a typical residence is 1 foot of passive vent opening per every 150 square feet of attic size. To keep air flowing your roof needs just the right amount of attic ventilation. That said air resistance and interference such as vent grates reduces the area of true ventilation. Attic ventilation keeps the air moving and stops mold from growing but too much ventilation can be just as bad as having none.

This characteristic of air may be used to help create a flow of air ventilating the attic. In all seasons the attic space is warmer than the outside air. Most building codes require a ratio of 1 150 ventilation space to attic floor space. The rule of thumb on the amount of vent space needed is approximately 1 sq.

The following product options will allow you to achieve an intake nfva of 528 square inches. Choose one of the following products to meet the recommended intake nfva of 528 square inches. Ideally the total vent space should be equally divided between lower soffit vents and upper vents at the roof peak. This results in a constant upward air movement due to the buoyancy of warmer air.

The uniform building code requires that the amount of venting area in the attic be equal to 1 150 of the area of the floor and in most circumstances it allows a ratio of 1 300 if the venting area. Ventilation can be accomplished using various products and techniques. Do not use gable vents because it s possible to draw rain and snow into the attic. Throughout the roofing industry there is a widespread lack of agreement over adequate attic ventilation.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Much of the debate stems from the tremendous variation in climate across north america. Is ridge vent alone sufficient for proper ventilation in your attic. But what type works best and how do you know when enough is enough.

In other words the entire vent opening doesn t count as vented space. 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. We hear this question quite often from zimmerman exteriors customers. Ft you divide that by 150 to get 10 sq.

Of vent for every 300 sq. Before we explore how to ventilate an attic space it is prudent to understand how much ventilation is needed. Allows cool dry air to enter the attic. So if your attic is 1 500 sq.