R-Value Information

Tech Hotline No. 0610-BSc
Continuous Insulation (ci) Requirements for
Steel Framed Walls in the United States

Continuous insulation (ci) is a required component of most steel framed wall construction in the United States. Table 1 shows relevant codes and standards and their prescriptive ci R-value requirements in relation to US Department of Energy (DOE) defined climate zones (Figure 1). StoTherm® Systems1 with built-in continuous insulation readily meet these requirements.

StoTherm ci R-Values:

1 inch
2 inches
3 inches
4 inches
5 inches
6 inches
7 inches
8 inches
3.8
7.6
11.4
15.2
19.0
22.8
26.6
28.8

Table 1. CI requirements expressed as R-value for opaque above grade steel framed wall assemblies

Code /Standard
Climate Zone
1
2
3
4
5
6
7
8
IBC and IECC(1) – 2009ASHRAE 90.1(2) – 2010 NR NR7.5(R) 3.87.5(R) 7.5 7.5 7.5 7.515.6(R) 7.518.8(R)
IRC and IECC(1) – 2009 5.0(3) 5.0(3) 5.0(3) 5.0(3)(XM) 10.0(4)(M4) 10.0(4) 10.0(4) 10.0(4)
ASHRAE 189.1(5) – 2009 5.0 5.010.0(R) 5.010.0(R) 10.0 10.0 10.0 10.018.8(R) 10.021.9(R)
IGCC 2010(5)
Achieve prescriptive ci R-values or comply with ASHRAE 189.1-2009
IBC and IECC(1) – 2012 5.0 5.07.5(R) 5.0(3) 7.5 7.5 7.5 7.515.6(R) 7.517.5(R)
IRC and IECC(1) – 2009
Varies: decreases with increasing cavity insulation or increased (24 in oc) stud spacing

NR = No Requirement, R=Group ‘R’ residential occupancy such as apartment, condominium, hotel, nursing home, XM = Except Marine, M4 = Includes Marine 4

1. IBC or IRC and IECC: the IBC, International Building Code, references the IECC (International Energy Conservation Code) for energy efficiency. The IRC, International Residential Code ci requirements are the same as the IECC requirements for Residential Energy Efficiency.
2. ASHRAE 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings, is essentially the basis for the IECC – 2009 energy efficiency requirements.
3. Less or no ci permissible with increasing cavity insulation R-value.
4. Less ci permissible with increasing cavity insulation R-value.
5. ASHRAE 189.1- 2009, Standard for the Design of High Performance Green Buildings Except Low-Rise Residential Buildings
6. IGCC, International Green Construction Code, scheduled for publication in Spring, 2012.