Proper Attic Ventilation
 The
most efficient attic ventilation allows a constant flow of air in and
out of the attic through a balanced system of intake and exhaust vents.
Installed in the lower and upper portions of your attic, this system
of intake and exhaust vents creates a constant upward draft of air,
which helps to equalize attic temperature with the living space below,
making the living space easier to cool or heat, reducing unnecessary
strain on air conditioning and heating equipment, and improving the
efficiency of attic insulation.
The 50 - 50 Rule
Proper attic ventilation depends upon balance in the system of air
intake and air exhaust. Roofing engineers recommend the “50 - 50 Rule”
for maintaining proper ventilation balance: 50 percent of the airflow
should be allotted to intake vents, and 50 percent of the airflow should
be allotted to exhaust vents. The measurement used in determining airflow
is called “Net Free Area”.
Net Free Area
The ventilation area of any vent, that is the unobstructed area through
which air can freely pass, is called “Net Free Area”. All Ventamatic
Static Vent listings include Net Free area figures. The Federal Housing
Administration (FHA) and most building codes recommend a minimum of
1 square foot of attic ventilation for every 300 square feet of attic
space. This is a minimum recommendation. More ventilation may be required
in weather extremes or by specific building codes in your area. See
the back page for assistance in calculating the ventilation requirements
of your attic.
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