Should battens be installed?

We are getting ready to have a dark brown 26 gauge exposed fastener metal roofing put on our house. The roofer will be doing a complete tear off of our old shingles. He will be installing a synthetic underlayment onto the deck. The roofer has suggested that our house would be more energy efficient if he attaches horizontal battens on the top of the roof deck before screwing down the metal panels. Our house already has a continuous vented soffit and the roofer will be installing a vented ridge cap. I would love to have your professional opinion and advice concerning the battens. Would they help with energy efficiency? Even though we have blown insulation in our attic, I am also wondering if the air gap created by the battens lessens one's chance of getting mold in the attic from condensation formed on the metal. Please give me your advice as I desperately want to be a happy first time metal roof homeowner.

Charlie,

Is the roof solid decking? Is the attic vented and if so, how?

Yes, the roof is solid decking. We have continuous soffit vents and gable vents for the attic. The roofer said that he would be installing a vented ridge cap for ventilation, too.

I wouldn't worry much about the battens in this case. The metal will mostly cool to the outside here via convection and the venting (i.e. ridge vent and soffit) will handle the moisture.