Attic Air Flows

The insulation will resist heat transfer into the house.

Attic air flows.

Whole house fans powered attic fans. The most common mistake homeowners make when installing insulation is to block the flow of air at the eaves. Gable vents may circulate air through only a small percentage of your attic. Ventilation manufacturers assign an nfa value to the non motorized vents they make.

Vents come in various styles. One common problem is caused by ice buildup along the edges of a roof. These fans may be controlled by a switch or a thermostat which detects heat build up in the attic space and automatically exhausts the attic space. 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.

Grab a flashlight and inspect your attic during the winter. Static roof line vents are effective for ventilation but generally aren t recommended due to issues with leaks. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Hot air exhaust vents located at the peak of the roof allow hot air to escape.

If you see dampness or frost you need better roof ventilation and some attic vents. For the best results place roof ventilation near the roof s peak and soffit vents in the eaves. Make sure there is air flow from the eaves. The biggest chore is adjusting the air flow valves known as dampers in the ductwork.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. 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. Air flows in through the soffit vents and out through the roof vents. And when the ductwork is in an attic fine tuning the process can be a system of trial and error demanding time.

The ice traps water behind it allowing the water to seep back under the shingles and leak through the roof. This is normally the point where air enters your attic. 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 air to enter the attic.