I have a bungelow house with a metal roof. IN the attic space I am planning to convert it into living space and would like to insulate and drywall is off. When I look at the underside of the roof I see there is boards running length-wise and a space of a few inches in between them. In the spaces in between I see the underside of the metal roof. How would I go about insulating that? Would a spray insulation be best or batts? I am worried about condensation and making sure i do the job right. if spray, what happens in 10 years when i need a roof? Thanks for any help.