We are considering adding a sunroom on to our home on a 14'x20' deck using 2x6's spaced 16" apart...this is over a poured concrete patio and under an existing second-story deck...using the deck idea so existing 6x6 posts and footings can be used instead of busting up the patio and pouring new....we will use 5/8" sub-flooring and plan to install hardwood on this & heat with a pellet stove in the long winters here in WI....I'm wondering what type of insulation I should use underneath between the floor joists, vapor barrier recommendations etc....note that to have sunroom floor even with first-floor, there will be less than 1' of clearance under the 2x6's....any suggestions appreciated!

After reading a number of other posts...Is it as simple as building up the sub-floor structure with insulated/vapor-barrier materials:

hardwood
hardwood underlayment
sub-floor
vapor barrier
foam sheet insulation
plywood sheathing (weather-treated)
joists (exterior weather-treated)

I have enough room so that it will not be a problem making the hardwood level with the first-floor as long as I know before hanging joists how much build-up will be required.