Attic Insulation

I have just contacted radiant barrier contractor who suggests that I add 11.5 inches of blown-in fibreglass to my existing 22.5 inches. The house is 15 years old and the existing insulation has been disturbed by contractors.

This is in addition to a sprayed-on radiation barrier.

Also suggested is a fancy thermal zipper enclosure for the access stairs.

Is all this insulation necessary? It entitles me to 1/2 off the price of the radiant barrier. I am always suspect of these deals.