C402.2.3 Above-grade walls. The minimum thermal resistance (R-value) of materials installed in the wall cavity between the framing members and continuously on the walls shall be as specified in Table C402.1.3, based on framing type and construction materials used in the wall assembly. The R-value of integral insulation installed in concrete masonry units (CMU) shall not be used in determining compliance with Table C402.1.3 except as otherwise noted in the table. In determining compliance with Table C402.1.4, the use of the U-factor of concrete masonry units with integral insulation shall be permitted.

"Mass walls" where used as a component in the thermal envelope of a building shall comply with one of the following:

1. Weigh not less than 35 psf (170 kg/m2) of wall surface area.

2. Weigh not less than 25 psf (120 kg/m2) of wall surface area where the material weight is not more than 120 pounds per cubic foot (pcf) (1,900 kg/m3).

3. Have a heat capacity exceeding 7 Btu/ft2 x °F (144 kJ/m2 x K).

4. Have a heat capacity exceeding 5 Btu/ft2 x °F (103 kJ/m2 x K) where the material weight is not more than 120 pcf (1900 kg/m3).