I had a roof replace recently. I requested ridge vents to replace my turtle vents. The person who wrote my contract strongly suggested ridge vents and thought ridge vent was the best choice. However, the project coordinator supplied turtle vents to be put on the roof.
Below is his reason from an email as why he changed the ticket order
"Ridge vent has an intake of 12.5 in.³ for every linear foot. Each turtle that has about 70 in.³ We could have installed 8 to 10 feet maximum of ridge vent. The total on that is only 100 in.³ to 120 in.³ whereas with the turtle vents just two of them would be superior."
He basically said my roof edge is too short to have ridge vent for proper ventilation.
Picture of my roof image2|690x180