2 years ago I replaced a section and put on turbine vent and was planning on adding more vents as I work on the other sides. I am working on one side now and decided to look at the turbine vents after it rained. The bearings are already shot and before that hardly spinning anyways. Rain is coming in the attic and on top of the because of the pitch it dripping directly on the the decking and getting under the underlayment. So I have a some option to fix this. Since I only have one side done it wont take to much to do. Attic is 650 to 720 sq. My roof layout is shaped like a cross (so 4 valleys) with a 14-15/12 pitch for most of it but one section is a a little steeper. No soffits vents but might be able to add latter. I would be worried about only a few bays getting getting cooled and some of the rooms getting cold during the winter cause air is now passing the wall/celling. I attached some crap pic of the roof.
Option 1- Take the turbine out, put in a 12x12 plug, replace and add singles as needed, install ridge vent. I know they work better with soffits but they give more even ventilation. They also look better then 4-7 slant vents. May add some gable vents later on or soffits
Option 2- Replace turbine vent with slant vent and then add more. However, I would add some to the side that is already shingled. They are kind of big and any hail/rain noise would sound annoying just like the aluminum siding I have. Also with how steep it is water may leak in one. I find They are only rated for 8/12. May add some gable vents later on or soffits
Option 3- Replace turbine with powered fan that is H.E. with humidity and temp sensors. May add gable vents on. May add some gable vents later on or soffits
Option 4- find way to keep water off the decking and drip on to plastic sheet or bucket. Then just use slant vents.