International Energy Conservation Code

Section 502.2.1     Roof assembly

The minimum thermal resistance (R-value) of the insulating material installed either between the roof framing or continuously on the roof assembly shall be as specified in Table 502.2(1), based on construction materials used in the roof assembly.

Code Interpretation

This code establishes the minimum R-value required for insulation above the deck on commercial buildings. The thermal R-value required for insulation applied entirely above the deck is based on climate zones in the chart listed below. The code indicates that the thermal R-value prescribed is for the insulation only and does not include other building materials or air films.

Climate Zone  R-Value

  • 1          15
  • 2          20
  • 3          20
  • 4          20
  • 5          20
  • 6          20
  • 7          25
  • 8          25

TABLE 502.2(1)

 Building Envelope Requirements – Opaque Assemblies Roofs Insulation Entirely Above Deck