I live in Nova Scotia, Canada - Climate Zone 6 - and am considering installing a through-fastened steel roof (panels 36'wide cut to length). My house has a vaulted ceiling (no attic). The roofing deck consist of 2x6" T&G pine boards running from eaves to ridge and is visible from the interior as my finished ceiling.
The approach that I am considering using to install the fastened through metal panels on the BACK roof (4/12 pitch), in sequence from start to finish:
strip entire roof down to deck;
cover 2x6' pine roof deck with either an air barrier or vapor barrier. What is recommended at this stage of the install of the roofing assemby? Air or Vapor barrier?
install two layers of 1 -1/2 inch EPS expanded polystyrene;
cover with a high temperature roof underlayment; Air or Vapor underlayment?
installing 1x4" purlins; then
installing metal panels to purlins, leaving both eaves and ridge opened for air movement.
Would this be advisable? Any suggestions would be much appreciated.