[momark]

I plan to have a metal building put up to be used for a weekender house/cabin. If I have insulation blown in the attic joists do I still need some sort of insulation just under the metal roof? It will have a ridge vent system also.

 

[Windows on Wash]

No.

At that point, the insulation/envelope is at the attic floor. Between the combination of a well ventilated attic and a nice tight envelope, you should be able to mitigate condensation potential on the roof surface.

Is the roof going over a solid deck or over a system of purlins/battens?

Be sure to air seal prior to installing the insulation and that should help it stay even warmer and keep the moisture from moving into the attic and possibly condensing on the roof.

 

[momark]

It will be over a system of purlins and battens. Thanks for the tips.