Vapor barrier on deck

[SustainableSerenityAcres]

So we are close to the point of the platform building that we need to figure out the

insulation

and vapor barrier thing. We are pretty sure we are going to go with a mix of roll

insulation

and rigid foam to get up to R30 on the floor. The hubby has asked me to look into where the vapor barrier should go or if we should not use a vapor barrier. We are up in central NH, so a pretty cold and wet climate up here to begin with. Mainly looking for suggestions on if we should use something like plastic sheeting or Tyvek and if so should it go up under the T&G flooring or down on the bottom of the platform on top of the OSB?