I haven't posted many pics of our work but I thought this was an interesting venting solution that hasn't been discussed here, at least of late.
Our customer had major condensation issues with his old metal roof. The existing 2X6 rafters had little to no insulation and zero ventilation. We removed the existing metal roof and prepped the existing 1X decking for the installation of new materials.
TheHunter Panel does not call for a vapor barrier/underlayment but does recommend it. Weopted to install Titanium UDL 30 as you wouldunder a normal roof. We theninstalled a Cool Deck panel manufactured by Hunter. This had a 1" Rigid ISO spaced with 1X strips, laminatedto a 7/16" OSB coverboard. This was a fairly easy installation. With the exception of the screws required for fastening it cut and installed just like OSB.
Weinstalled ice guard inthe valleys and eve's as usual. We then Installed another layer of Titanium over thenew roof deck.A 16" SL Panel manufactured by Bridger Steel in Casper, WY was selected as the prefered covering. We had a bit of trouble keeping things square as the home is OLD and has been added onto a few times. For an old saggy roof I think it turned out pretty well.
As a bonus, it has snowed several time since with no sign of condensation!