SUMMARY:  Should I install a single gable vent in an enclosed attic space behind a knee wall, that hasn’t been properly encapsulated, in Climate Zone 2?

DETAILS:  
• The attic space is completely unvented:  no gable vents, no soffits, no ridge vent.

• I can install only one gable vent, because there’s only one exterior wall, and it’s big enough for only one vent.  The other end of the attic space ends with drywall, because there’s room on the other side with a cathedral ceiling.

• There were disintegrating fiberglass batts in the 5.5″ rafter bays, falling down, I removed about half of them.

• The underside of the roof sheathing is dry and perfect.

• There’s 3.5″ of batts behind the knee wall, I’m planning to add another 8.5″ of loose cellulose.  I’m also planning to pull up the plywood floor and put cellulose in the joist bays, making sure to add blocking under the knee wall first, see if I don’t.