I put a metal roof on mine and it is super.I would suggest not putting plywood or any kind of solid material under it as this has been known to cause condinsation.I put 1x6 under it.These are called perlins.I placed them about 16 in apart.It is a good roof.As far as loosing insulating factor,if you feel that you need it you can go inside and put in a ceiling.You want to make sure that you have ventilation at the ceiling in the heat so that the heat can escape.This is a good aspect of the metal roof.If you do decide to put it on get online or ask someone that knows and find out the proper way to install.It's not hard,but there are a few things that you should know.Good Luck