We’re redoing our insulation. How do I know if I need a vapor barrier.
You shouldn’t need a vapor barrier in your attic in Oakland as long as there is adequate ventilation to exhaust any moisture in the attic space. You should also check to make sure all sources of moisture are being vented through ductwork to the outside of the thermal envelope either through the roof or wall such as bathroom/laundry fans and clothes dryers.
Always a good idea to consult a qualified insulation installer for any further recommendations pertaining to your particular building.