Foamboard as a flooring insulator

[Rhende]

I have scavenged 3/4" x 5" tounge and groove (t&g) from a barn and want to use it as flooring in a pier and beam constructed house. subflooring in the house consist of 3/4" particle board, rolled felt and diagonally laid 8" T&G of yellow pine. I'll remove the particle board and felt...I want to lay down 15# felt atop the diagonally laid subfloor, then 1/2" sheets (4'x8') of foamboard...then lay down the finished flooring of 4" T&G...

Anyone have expereince with using this "sandwich" as means of floor insulation...does it appear stable over the longrun? There is currently no floor insulation other than particle board and felt. Recommendations as to type of foamboard?

 

[noseall]

stability-wise sounds o.k. not so sure on how reliable as an insulator though ? in the u.k. our building codes would probably ask for thicker insulation.