N1102.1.3

Section N1102.1.3 is titled 'R-value computation' and covers requirements for energy efficiency. The clarification that insulation installed in layers in an assembly shall be summed to determine the total R-value, the use of the manufacturer's settled R-value figure must be used for blown-in insulation, the exclusion of materials which are not allowed to be considered as insulating from R-value calculations, and the requirement to reduce the manufacturer's listed R-value for insulated siding where used as a continuous insulation element of the building thermal envelope is established. The purpose of this section is to declare allowances and limitations when calculating R-values.

The model shows a section of a wall which is having the cavity filled with 2 layers of fiberglass insulation.