On a house with eaves and gable vents but no ridge vents wind perpendicular to the ridge tends to create air flow along the floor of the attic but leave hot dead air in the roof peak left.
Gable vents vs roof vents.
This air then flows up the roof deck and out the ridge vent.
You would also have to cover up and close the gable vents because air would come in and go straight out the ridge.
Keeping the roof cool in the summer and because the outside air is drier than inside air in the cold weather it keeps the roof dry.
Gable vents are usually chosen for their visual appeal but can also serve as an exhaust vent.
Since we had the new roof we have had issues with ice dams as well as uncomfortable temperatures on the second floor of the house cold in winter and very hot in summer.
Ridge vents are much easier to install because they sit on top of the roof at the peak.
You merely have to climb up to the roof and place the ridge vent.
These vents are installed in the soffit the enclosed portion under the roof overhang and permit air to flow up under the roof and into the attic.
It will run the entire length of the gable roof peak.
Without ventilation unfinished attic spaces can end up having stagnant air.
Without any air movement temperatures in the attic soar in summer and plunge in winter.
The gable end vents were not closed up.
When the wind is perpendicular to the gable the cooler outside air enters the gable vent and drops to the floor of the attic before rising to exit at the other end again leaving zones of dead air right.
Many roofing contractors discourage using a gable vent with ridge vent and soffit vents because a gable vent interrupts the proper airflow and can cause the air current to flow perpendicular and unevenly throughout the attic.