Do I have to worry about condensation under the standing seam steel roofing, because several roofers have told me they woulod have to use a stick down moisture barrier like bituthane (sp?).
The only time you would need to use direct contact underlayment is when there is going to be a significant temperature difference between the two sides of a roof. In your case you haver placed insulation in the roof system to avoid that problem.
The space between the top of the roof, and the top of the insulatioon is where you need to be concerned about condensation. As long as there isnt a significant temperature difference within that area you are good to go.
As you state that there is a 1-1/2" vented space just above the insulation. That means that the material above that will be in the same temperatrure range on top as well as on the bottom.
Thank you, XXXXX XXXXX my theory by which I designed the roof system.