I should have described this better. Easy way,install R-19 first between foist and up tight to floor. Next install pex up tight to joist.Next install another layer of R-19 .This would be the same as site built and if there is a leak/tear in belly skin cold air does not affect whole floor cavity. Ins...

R-33 should be the minimum you install. If you check local bldg codes for Energy efficient homes they will point you in the right direction. Also insulation should be installed up tight to the floor, make sure your ducts are wrapped and your water lines mid depth in the insulation. Belly skin needs ...