The gable end vents were not closed up.
Gable vents vs roof vents.
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.
This air then flows up the roof deck and out the ridge vent.
Ridge vents are much easier to install because they sit on top of the roof at the peak.
It will run the entire length of the gable roof peak.
A new roof was installed 10 years ago at which time a ridge vent was added along all ridges at the suggestion of the roofer.
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.
You merely have to climb up to the roof and place the ridge 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.
You would also have to cover up and close the gable vents because air would come in and go straight out the ridge.
Installing functional gable vents can take some time as you will need to fit them into the gable end of the roof.
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.
Without any air movement temperatures in the attic soar in summer and plunge in winter.
They range in style from 6 inch round stainless steel vent covers that are placed in the soffit between each rafter to continuous vents that run the entire length of the soffit.
Without ventilation unfinished attic spaces can end up having stagnant air.