Q: The attic floor in my one-story house has six inches of insulation on it, but there is none on the attic roof. Would it keep the attic cooler in summer if I installed insulation up under the roof beams and if so, should this insulation have a vapor barrier facing up or down?
A: Insulation up against the roof would keep some heat out in the summer, but frankly, I don't think it would be worth the extra cost and effort. If your main interest is keeping it cooler, I think you would be better off installing a roof ventilating fan. If you do decide to put up the insulation, install it with the vapor barrier facing down.
Q: My attic has fiber glass batt insulation that has a Kraft paper facing on both sides. Does this mean my insulation has two vapor barriers?
A: No. There is a vapor barrier on only one side. If you look closely you will see there is a difference in the paper on one side -- it will be heavier, and if you tear it, there will be a layer of what looks like tar paper or asphalt on the inside of the paper. That side is the vapor barrier -- on the other side is plain brown paper.