Attic’s need continuous ventilation at the eave edge to draw fresh air in and remove trapped hot, moist and toxic air out through the roof exhaust vents.
The average ridge vent offers an 18 NFA per foot along the peak of the roof. To accomplish a balanced ventilation system the intake must provide an NFA of 9 or greater on each side. Most soffit designs don’t provide enough continuous NFA (Net Free Area of Ventilation) to work with roof exhaust requirements.
Resulting in most homes not being properly ventilated; and roof manufactures won’t provide warranty coverage on homes without proper ventilation.