Attic Ventilation Air Flow

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.

Attic ventilation air flow.

The most common mistake homeowners make when installing insulation is to block the flow of air at the eaves. Increased ventilation will make the entire roof cold and reduce or eliminate ice dams. To calculate the amount of ventilation you need for your home visit gaf s ventilation calculator now. Before we explore how to ventilate an attic space it is prudent to understand how much ventilation is needed.

In the summer natural air flow in a well vented attic moves super heated air out of the attic protecting roof shingles and removing moisture. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Air flows in through the soffit vents and out through the roof vents.

Ventilation can be accomplished using various products and techniques. The ice traps water behind it allowing the water to seep back under the shingles and leak through the roof. 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. These ice dams form when warm attic air melts the snow on the roof and the water refreezes along the colder edge of the roof.

In other words the entire vent opening doesn t count as vented space. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. Air follows the path of least resistance. A new roof is more than just shingles.

For the best results place roof ventilation near the roof s peak and soffit vents in the eaves. Grab a flashlight and inspect your attic during the winter. That said air resistance and interference such as vent grates reduces the area of true ventilation. Intake exhaust airflow in a house attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed.

Intake vents located at the lowest part of the roof under the eaves allow cool. The insulation will resist heat transfer into the house. Most building codes require a ratio of 1 150 ventilation space to attic floor space. Proper attic ventilation can help reduce the load on your air conditioner.