Code Communicator - New Requirements for Insulation

Architecting Insights

New Requirements for Insulation in Commercial Buildings

The 2009 IECC, International Energy Conservation Code includes requirements for minimum insulation in commercial construction that have changed significantly from those requirements we have used in the past.

For a commercial building, select the appropriate climate zone from Table 301.1, “Climate Zones, Moisture Regimes, and Warm-Humid Designations by State, County and Territory.”

Refer to Table 502.2 (1), “Building Envelope Requirements – Opaque Assemblies” for minimum R-values depending on the climate zone and the type of construction.

For example;  A metal framed building in climate zone 5A would require:

  • Roofs, Insulation above deck                    R-20 minimum, ci (continuous insulation)
  • Walls, Above Grade                                       R-13 + R-7.5 ci
  • Walls Below Grade                                          R-7.5 ci
  • Slab-on-Grade Floors                                    R-15 for 24” below

The minimum roof insulation is a significant change from the average roof insulation we are familiar with using.  Basically, 4” of insulation is required, with the only exception at roof drains.  At roof drains, the 4” of insulation can taper down to 3” within the area of the drain sump.

In metal stud walls, the requirement for continuous insulation in addition to the insulation within the stud space is new.  Provisions for continuous insulation also occur in masonry walls.

Traditionally, we have designed 2” rigid insulation below slab-on-grade at the perimeter of a building for 24” below the slab and down the inside face of the foundation wall. The requirement for R-15 requires we now use 3” insulation as our minimum standard.

In summary, refer to the minimum insulation requirements for the building’s climate zone and type of construction for current code.

USA Architects Code  Specialists, Tara Dohoney, HHS and Joy Cohen, AIA are happy to answer questions you have regarding the new code.  They can be contacted via email at