I’m in Baytown Texas which is on the southeast side of the Houston area climate zone 2. I started a diy attic insulation project. The attic has big gable vents on each side and no soffit vents. And a powered attic fan that’s never used. Sometimes I can literally feel a breeze up there. The attic has 2×4 ceiling joist, and on the living space side has shiplap boards with ceiling tiles attached to the shiplap. No Sheetrock. Which is nice when your trying to walk around up there. In between and on top of the 2×4 ceiling joist in the attic is yellow foil faced 2×4 size fiberglass insulation with the foil facing up towards the roof. My plan was to leave what was already there and add unfaced rolls of R-30 fiberglass perpendicular on top. This should get me up to at least R-40 or more. My question is can I just leave the old insulation with the foil face up and cover it up with unfaced R-30 fiberglass? In a lot of spots it’s dusty and the foil is crumbly. Also should I even worry about having a “kraft face” vapor barrier on the living space side? Do I even need that in the Houston area climate zone 2? Eventually we plan to remove the ceiling tiles because they’re  ugly and attach sheetrock to the shiplap. Based on what I’ve read, painted sheetrock acts as kind of a vapor barrier.