The minimum thermal resistance (R-value) of the insulating material installed either between the floor framing or continuously on the floor assembly shall be as specified in Table C402.2, based on construction materials used in the floor assembly.
“Mass floors” shall include floors weighing not less than:
1. 35 psf (170 kg/m2) of floor surface area; or
2. 25 psf (120 kg/m2) of floor surface area if the material weight is not more than 120 pcf (1,900 kg/m3).