Recommended installation practices for refrigeration piping insulation and vapor barriers include ensuring a clean, dry, and contaminant-free surface before installation. The insulation material should be cut to fit snugly around the piping, with all seams and joints properly sealed. The vapor barrier should be installed in a continuous, unbroken layer, with all overlaps and seams securely taped. Additionally, the insulation and vapor barrier should be securely fastened to the piping using approved methods and materials.