[Joasis]

One of my comany's specialties is metal roofing, and we have done it both ways....but the safe answer is this: Felt is dirt cheap, why not? In my new construction, I do not deck the roof, but rather use 2X for strapping, and roll insulation before metal....you would not believe the break on the cooling load on a typical home......in Oklahoma, attic temps in the summer can easily reach 140 degrees....with insulation under the metal, temps are 40 degrees or more lower.

 

[Joasis]

most codes and good roofing practice would require felt. with metal roofing its also a good idea to put a layer of red rosin paper between the felt "or Ice&water shield" and the metal that way it wont potentialy stick to it and cause oil canning and would allow for expansion.

RooferJim
www.jbennetteroofing.com

And of course, there are a lot of styles of metal roofing....what we install,(vertical panel) for instance, does not oil can.