Welcome to the forum Breleigh! I am assuming you are doing this over a concrete floor? I have heard of this being done.Laying 1" styro (usually about R8) then tongue and groove plywood fastened to floor then underpad and laminate. R19 seems a little extreme you would need like 2-1/2 " of styrofoam? Over concrete almost any closed cell styrofoam will give a dramatic difference in warmth because you are creating a thermal break from the concrete surface, so i don't think it is necessary to go super thick. good luck!
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