Radiant barrier for the attic: I live in Dallas in a 20 year old home?

I am debating whether to spend either $800 on a radiant heat barrier or $1,200 on additional attic insulation. I am told that my current attic insulation is only 4 inches thick and it is a two story home. I have two power attic fans installed. Which product gives the most bang for the buck?

Answers:
Try putting that foil backed styro/foam on the under side of the rafters

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